Technical Articles

[3stagevtec]

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Home Speakers Glossary

2-conductor speaker wire
Speaker wire that contains two separate wire conductors within the jacket, one used for the positive speaker terminal and one for the negative.

4-conductor speaker wire
Speaker wire that contains four separate wire conductors within the jacket, two each for the positive speaker terminals and two each for the negative speaker terminals. A 4-conductor speaker wire can be used with stereo-input speakers, including some in-wall and outdoor speakers, and in multiroom setups where the speakers are somewhat close together to send two different signals using one cable. You can also double-up the positive and negative wires for use with a single speaker when bi-wiring and bi-amping the speaker.

Acoustic suspension
A type of speaker enclosure that uses a sealed box to provide tight, accurate bass response. It gives up some efficiency to provide bass that is more accurate and controlled, so compared to a bass reflex design, it may require more amplifier power to play at the same volume level. See also bass reflex.

Automatic speaker calibration
Receivers with this feature analyze and automatically adjust the sound of connected speakers. The receiver sends a series of test signals to each speaker in your surround sound system, then measures the response with an included calibration microphone to optimize the speakers' volume level, time delay settings, and frequency response — making speaker setup easier and usually more accurate than manual methods. The most advanced auto calibration systems allow multiple measurements to be taken from different listening positions in the room to provide even greater sonic accuracy. Watch our video on automatic speaker calibration to see how it's done.

Bass reflex
A type of speaker enclosure that includes a "tuned" port or passive radiator to increase and extend bass response (by releasing some of the energy created by the inward movement of the woofer cone).

Bass reflex designs are more power-efficient than acoustic suspension designs — they'll play louder than an acoustic suspension speaker when driven with the same amplifier power. But they may sacrifice some bass accuracy in exchange for the added bass output.

Bi-amping and bi-wiring
It's becoming more common for higher-performance speakers to include dual sets of terminals, usually binding posts (see terminals, below). Models with dual terminals almost always also feature a special type of crossover with separate "high-pass" and "low-pass" sections.

Speakers with dual sets of terminals work fine when used with a single set of speaker cables. In fact, they usually come from the factory set up for conventional operation, with "jumpers" installed between the two sets. These jumpers can be easily removed for bi-amping or bi-wiring.

Bi-amping means that instead of driving a speaker full-range with a single channel of amplification through a single set of speaker cables, you actually connect two sets of cables, with each set carrying the signal from a separate amplifier (or amp channel). This way, both low-frequency drivers (woofers) and high-frequency drivers (tweeters) receive dedicated amplification.
Bi-wiring involves connecting two sets of cables to your speakers, like bi-amping, but both sets of cables connect to the same set of output connectors on your receiver or amplifier. Bi-wiring doesn't deliver more wattage to your speakers, so it doesn't offer as dramatic a sonic improvement as bi-amping. Still, many audiophiles find that it offers subtle improvements in imaging and detail.
You can also check out DaveB's blog posts on bi-amping and bi-wiring for more information.

Bipole
A speaker design that uses two sets of drivers to generate equal amounts of sound both forward and backward, or side to side, with the two sounds being "in phase." In a home theater setup, bipole speakers are particularly effective at creating a full, diffuse soundfield when used as surround speakers placed behind the listening position. Some speakers offer both bipole and dipole modes.

Center channel speaker
The center channel speaker reproduces almost all of a movie's dialogue and much of the special effects. Since its purpose is to keep sound anchored to the on-screen action, a good center channel speaker is crucial for a well-balanced home theater system. It's usually mounted on top of your TV or directly below it. See our articles on choosing home theater speakers and speaker placement for home theater for more info.

CL2/CL3 rating
A rating given to speaker wire by the Underwriters Laboratories, it means that the wire has been thoroughly tested for safety in case of fire or electric shock, and approved for in-wall use. The CL2 (Class 2) rating means the cable is certified for use in homes. A CL3 (Class 3) rated cable has a higher threshold for heat, so it's certified for commercial or industrial buildings. Some CL3 cables are also separately rated for direct burial, making them useful for outdoor installations.

If you're going to install in-wall, in-ceiling, or outdoor speakers in your home, then you're going to need to check which rating your local code requires. You can also check out our in-wall wiring guide for more info.

Coloration
Any change in the character of a sound that reduces accuracy, such as an over- or under-emphasis of certain frequencies.

Connectors (pins, plugs, etc.) (Click for pictures)
There are several different ways to connect the cables from your receiver or amplifier to your speakers. Bare wire connections are acceptable, especially with "spring clip" terminals. However, there are other connector types that provide more solid and secure connections, especially with binding post terminals.

Spade connectors are compatible with most binding post terminals. A spade fits around the terminal's central threaded post, allowing you to then tighten the collar down on the spade for a snug, secure connection. But keep in mind, some electronics now have terminals that prohibit the use of spade connectors.
Pin-type connectors will work with both spring clip and binding post terminals. This is probably the best type for connecting a thick, heavy-gauge wire to a small spring clip connector. On a 5-way binding post, this slender pin will also fit the hole that's back near the base of the central post (see binding post illustration, below). You can then tighten the collar down against it.
Banana plugs will plug straight into the center of 5-way binding posts. They make a quick and convenient connection — nothing to loosen or tighten.
Double-banana plugs are the same as banana plugs, except the positive and negative banana connectors are both fixed in a molded housing that spaces them 3/4" apart. (These are even quicker and easier to connect than regular, single banana plugs — as long as the terminals on your speakers and/or receiver are true 5-way binding posts with the proper spacing.)

Crossover
A circuit that divides the frequency spectrum into two or more parts. A crossover acts as a filter, allowing certain frequencies to pass through to the speaker while blocking others. It's the crossover's job to send only high frequencies to the tweeter and only low frequencies to the woofer. (And midrange frequencies to the midrange driver in a 3-way speaker.)

A high-pass crossover allows only frequencies above the "crossover frequency" to pass through, while a low-pass crossover (common in powered subwoofers) allows only frequencies below the crossover frequency to pass through. A "bandpass" crossover combines a high-pass and a low-pass so that the driver (often a midrange unit) only sees a restricted band of middle frequencies.

Decibel (dB)
The standard unit of measure for expressing relative power or amplitude differences. With audio, it represents loudness. One dB is the smallest change in loudness most people can detect. A 1 dB difference is barely noticeable, but a 10 dB difference is big — a speaker playing at 10 dB higher volume will sound roughly twice as loud.

Another amazing dB fact: For any given set of speakers, each 3 dB increase in volume level requires a doubling of the amplifier power.

Diaphragm
The part of a speaker driver that moves, producing the sound. Each diaphragm is directly connected to a voice coil. The diaphragm for a woofer is a cone, while for a tweeter, it's often a dome.

Diffusion
The scattering of sound. Diffusion reduces the ability of a listener to pinpoint the actual location of a speaker, a useful quality in surround speakers. Diffuse surrounds create a wraparound soundfield that draws you into the on-screen action.

Dipole
A speaker design that uses two sets of drivers to generate equal amounts of sound both forward and backward, or side to side, with the two sounds being "out of phase." Dipoles are often used as surround speakers, and are very effective at creating a diffuse soundfield when placed on the sides of the listening position. Some speakers offer both dipole and bipole modes.

Direct and reflected sound
The sound that you hear from your listening/viewing position is a combination of the direct sound that travels straight from your speakers to your ears, and the indirect, reflected sound — the sound from your speakers that bounces off the walls, floor, ceiling or furniture before it reaches your ears.

Dispersion
The degree to which a speaker's sound is spread over the listening area.

Driver
Any individual diaphragm (cone, dome, etc.) within a speaker that compresses and rarefies the air to create sound waves, such as a woofer, tweeter, midrange, etc.

Dynamic range
The difference between loud and soft sounds. A speaker with wide dynamic range — one that can reproduce the sudden and wide changes between loud and soft sounds in music and video soundtracks — will sound more realistic (all other things being equal).

Efficiency
Although a speaker's efficiency rating is almost always correlated to its sensitivity rating, it is actually a different measurement. The efficiency rating for a speaker is a measure of how well a speaker converts watts of electrical power into watts of acoustical power. Most speakers have a very low efficiency rating — between 1% and 10% — so manufacturers rarely provide this information, choosing instead to list sensitivity ratings.

Flat
When a speaker's response is described as "flat," that's a good thing. It means that the speaker can accurately reproduce a signal that is fed to it without adding unnatural coloration to the sound. Specific frequencies don't sound too loud or too soft.

Frequency response
The human ear responds to frequencies from approximately 20 to 20,000 cycles-per-second, or Hertz. A speaker's frequency response indicates how much of that range can be reproduced.

Front speakers
In home theater, the front left and right speakers deliver a wide soundstage that blends with the video to create a more realistic and exciting movie experience. In addition to reproducing the musical score, front speakers work with your center channel to reproduce the special effects, along with any on-screen action that moves left to right or vice versa. The front left and right speakers in your home theater system also act as the left and right stereo speakers for listening to music. See our articles on choosing home theater speakers and speaker placement for home theater for more info.

Hertz (Hz)
The unit of sound frequency; one Hz is equal to one cycle per second. The range of human hearing is 20-20,000 Hz. Points of reference: low "E" on a bass guitar is 41 Hz; middle "C" on a piano is 262 Hz; cymbals can go out to 15,000 Hz.

Imaging
The ability of a speaker to reproduce spatial information in a recording so that you can visualize the relative positioning of individual voices and instruments as you're listening.

Impedance
The load value (in ohms) that the speakers present to the amplifier — the amount of resistance to the flow of current. While playing music, a speaker's actual impedance constantly fluctuates; however, speakers are usually given a single nominal impedance rating for easy comparison. Low-impedance speakers (4 ohms or less) can cause problems with receivers or amplifiers that are not designed to deliver large amounts of current.

In-wall/in-ceiling speakers
Speakers designed specifically for placement inside your wall or ceiling. They work the same as regular speakers, but mount flush with your drywall. The space behind your wall or ceiling actually acts as a giant cabinet, so these speakers can produce more bass than standalone speakers. Many people prefer in-wall or in-ceiling speakers because they don't take up the floor or shelf space of traditional speakers, and can be painted to match the room's décor. Check out our articles on choosing, placing, and installing in-wall or in-ceiling speakers for more information.

Kilohertz (kHz)
One thousand Hertz.

LFE input
Found on some powered subwoofers, this special preamp-level input accepts the "Low Frequency Effects" signal that's output by digital 5.1-, 6.1-, or 7.1-channel home theater receivers, ensuring proper bass reproduction. This type of input doesn't route the signal through any processing inside the sub which could potentially interfere with the low-pass crossover built into the receiver's bass management circuitry.

Some powered subs feature an unfiltered LFE input/output — the output sends full-range signals minus the low frequencies back to a receiver or preamplifier's "main in" jacks for even more precise sonic control.

Line-level (Preamp) connections
These connections carry the low-voltage analog audio signals from source components, such as CD and DVD players, to your preamplifier or receiver. Generally, these connections are made with RCA patch cords, also called interconnects. See also speaker-level connections.

Midrange
Generally considered to be the range of frequencies above bass and below treble that our ears are most sensitive to, which includes most vocal and instrumental sounds. Sometimes refers to a driver designed to reproduce these frequencies.

Motor structure
The part of the speaker that moves a diaphragm to produce sound. The motor structure basically consists of a voice coil that sits inside a cylindrical magnet. Alternating current is pumped through the voice coil, which constantly changes its magnetic polarity. As the voice coil alternates between being attracted to and repelled by the magnet, it moves the attached driver to create sound.

Neodymium
A material used in some speaker magnets. Neodymium magnets are smaller and more powerful than conventional speaker magnets.

Outdoor speakers
Speakers that are designed specifically for placement outside your home. Since outdoor environments are much more open than spaces inside your home, many outdoor speakers are designed to project sound over a larger area and to provide a little more bass than your typical indoor speaker. They're also built to be weather resistant to withstand assault from the elements. See our article on choosing outdoor speakers and our video on outdoor speaker installation for more information.

Passive radiator
A type of bass reflex speaker enclosure that includes a "passive" woofer in addition to the main woofer. The passive woofer isn't powered, but moves in response to changes in air pressure inside the cabinet that are caused by movement of the main woofer. Passive radiators are often used in speaker cabinets too small for a properly tuned port. Plus, they avoid some of the issues associated with ports such as port turbulence, which can sometimes lead to a low-pitched whistling noise coming from the port. However, passive radiators tend to be more complex to design, so you'll typically pay more for speakers with passive radiators than similar ported models.

Phase
Refers to the timing relationship of two or more signals or sound waves. It's especially important to be sure that your stereo speakers are playing "in phase." This means that the drivers (woofers and tweeters) of your right and left speakers are moving in and out at the same time.

If your stereo speakers are "out of phase" — that is, with one set of positive and negative leads reversed — you'll hear significantly less bass, and instead of producing a strong center image, the sound tends to stay localized at the speakers. To learn how to be sure your speakers are in phase, check the Home Speakers FAQ.

Phase control
A 2-position switch found on some powered subwoofers that lets you delay the subwoofer's output slightly so that it is in phase with the output from your main speakers.

Power handling
A measure of how much amplifier power, in watts, a speaker can take before it is damaged.

Resonance
When a component or system vibrates more at a certain frequency than at any other frequency. In a speaker system, resonance with the speaker enclosure or any of the components can lead to colorations in the sound.

RMS
A term used to indicate the average level of power that a receiver or amplifier can sustain over a given period of time. Average power ratings (ex: 100 watts RMS) provide a more realistic assessment of your amp's performance than peak power (ex: 400 watts peak/dynamic power) since an amp can only sustain peak power for a short period of time. (RMS stands for "root mean square," which is one of the mathematical methods used to calculate an amp's average power output. While it isn't an accurate descriptor of the measurements themselves, it's commonly used throughout the industry to denote the average power rating.)

Rough-in bracket
A mounting bracket used as a placeholder for in-wall and in-ceiling speakers in homes under construction or undergoing heavy renovation. If you choose to install one before the dry wall goes up, the drywaller will cut a hole for your speaker in the drywall for you, making speaker installation easier.

Satellite speaker
A small speaker with limited bass response that's often designed to be used with a matching subwoofer.

Sensitivity
A sensitivity rating tells you how effectively a speaker converts power (watts) into volume (decibels). The higher the rating, the louder your speakers will play with a given amount of amplifier power. Sensitivity is often measured by driving a speaker with one watt and measuring the loudness in decibels at one meter.

The chart below illustrates that a few dB in sensitivity can make a big difference:

Speaker Sensitivity rating Power needed
to produce a given volume
Speaker A 85 dB 100 watts
Speaker B 88 dB 50 watts
Speaker C 91 dB 25 watts
A speaker with a sensitivity rating that's 3 dB higher than another
speaker's only needs half as much power to deliver the same amount of sound.

Soundstaging
A stereo or home theater system's ability to present music, dialogue, and other sounds as taking place within a physical space with definite width, height, and depth. The individual vocal and instrumental "images" are part of the "soundstage."

SPL (sound pressure level)
The intensity or volume level of sound (measured on the dB scale). See sensitivity, above.

Speaker-level connections
These carry the higher-voltage, higher-current signals produced by a power amp or receiver to drive a speaker. These connections are made with speaker cables. See also line-level connections.

Standing waves
Standing waves occur when the sound from your speakers is reflected back and forth between the parallel surfaces in your room: the side walls, the front and rear wall, and the floor and ceiling. This effects amplifies some frequencies while others might get canceled out, creating areas of differing sound pressure or loudness around your room.

Subwoofer
A speaker specially designed to reproduce a range of very low frequencies only (the bass). The typical range for a subwoofer is about 20-200 Hz. A "powered subwoofer" includes a built-in amplifier to drive the speaker. See our articles on how to choose a sub and tuning your sub for more info.

Surround
Connects a driver's diaphragm to its basket. The two most common surround materials are rubber and foam. Rubber typically lasts longer than foam, especially in warm, moist climates, but tends to cost more.

Surround speakers
In a home theater system, the speakers located beside or behind the listening/viewing position. These speakers can be mounted on the walls, placed on stands, or set on bookshelves. They help create an enveloping three-dimensional soundstage by reproducing the surround information on video soundtracks and music recordings encoded with surround sound. For details, check out our nuts and bolts discussion of the different surround sound formats.

Some multichannel movie soundtracks also take advantage of surround back speakers. These speakers are used in addition to the regular surround speakers mentioned above, and can either be a pair of speakers placed behind and slightly to the sides of the listening area, or a single speaker directly behind it. You'll need a six- or seven-channel receiver for this type of setup, but adding surround back speakers can give you even more convincing wraparound effects. See our article on choosing home theater speakers for more info. You can also watch our video or read our article on speaker placement for more tips.

Terminals
You probably don't think about the connectors on the back of your speakers until you go to hook them up. There are two basic types: spring clips and binding posts.

Spring clip terminals are usually found on lower-priced speakers, and low- to medium-priced receivers. They work best with bare wire connections with small-gauge speaker wire, or pin-type connectors.
Binding post terminals are a sturdier, more versatile type of speaker jack, often found on higher-quality speakers and receivers, and on most amplifiers. They're threaded, so you can tighten them down against the wire or connector for an extra-snug connection.

A common variety of binding post, especially for speakers, is known as a "5-way" binding post. This type accepts bare wire, pin connectors, spade connectors, banana plugs, and double-banana plugs.

Timbre
Pronounced "tam-burr." The quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature — for instance, why a trumpet and a saxophone sound different when they play the same note.

Transducer
Any device that converts a signal from one physical form to another. Examples: a phono cartridge (mechanical to electrical); a speaker (electrical to mechanical).

Transient
A short-lived aspect of a signal, such as the attack and decay of musical tones. A speaker that can react quickly to rapid changes in the music is said to have good "transient response."

Tweeter
A small, lightweight driver that reproduces the highest musical frequencies, like violins, cymbals, female vocals, etc. The typical range for a tweeter is everything above 2,000 Hz or so.


Video shielding
A way of containing a speaker's magnetic energy inside its enclosure. This is usually achieved by placing another speaker magnet back-to-back with the existing one so that the two magnetic fields cancel each other. Shielding may also be achieved by lining the inside of the speaker cabinet with metal.

Video shielding is important for home theater speakers — especially the center channel speaker — because if an unshielded speaker is placed too close to a tube TV, the magnetic energy can cause picture distortion and even permanently damage the TV's picture tube.

Voice coil
The cylindrical coil of wire that moves in the magnetic field of a dynamic driver. The voice coil is bonded to the diaphragm, which actually produces the sound.

Voice-matching
When speakers possess a similar timbre or tonal quality. Voice-matched (or timbre-matched) speakers in a home theater system will result in more seamless, consistent, convincing wraparound sound. A good way to get voice-matched speakers is to stay within a family or series of speakers from a single manufacturer, or to get a pre-matched multi-speaker system. Check out our article on choosing speakers for more info.

Watt
A unit of power. Named after James Watt for his contributions to the development of the steam engine.

Wire gauge
The "gauge" (or AWG) is a unit of measure used to describe the diameter of round, solid wires, with 0000 gauge (or 4/0) being the largest possible diameter up to 46 gauge being the smallest possible diameter. Speaker wire typically ranges in gauge from 18 AWG to 10 AWG. The larger the gauge, the lower the resistance of the wire, giving you a better, more accurate signal transfer where long runs are necessary. You can also check out our in-wall wiring guide for more info.

Woofer
A type of driver that features a cone-shaped diaphragm, commonly used for producing the mid- and low-frequency portions of the music signal.






Source
http://www.crutchfield.com/S-MLIdlc3FE4h/learn/learningcenter/home/speakers_glossary.html

[3stagevtec]

Audio Terms For Tonal Accuracy

Airy: Spacious. Open. Instruments sound like they are surrounded by a large reflective space full of air. Good reproduction of high-frequency reflections. High-frequency response extends to 15 or 20 kHz.

Bassy: Emphasized low frequencies below about 200 Hz.

Blanketed: Weak highs, as if a blanket were put over the speakers.

Bloated: Excessive mid-bass around 250 Hz. Poorly damped low frequencies, low-frequency resonances. See tubby.

Blurred: Poor transient response. Vague stereo imaging, not focused.

Boomy: Excessive bass around 125 Hz. Poorly damped low frequencies or low-frequency resonances.

Boxy: Having resonances as if the music were enclosed in a box. Sometimes an emphasis around 250 to 500 Hz.

Breathy: Audible breath sounds in woodwinds and reeds such as flute or sax. Good response in the upper-mids or highs.

Bright: High-frequency emphasis. Harmonics are strong relative to fundamentals.

Chesty: The vocalist sounds like their chest is too big. A bump in the low-frequency response around 125 to 250 Hz.

Clear: See Transparent.

Colored: Having timbres that are not true to life. Non-flat response, peaks or dips.

Crisp: Extended high-frequency response, especially with cymbals.

Dark: Opposite of bright. Weak high frequencies.

Delicate: High frequencies extending to 15 or 20 kHz without peaks.

Depth: A sense of distance (near to far) of different instruments.

Detailed: Easy to hear tiny details in the music; articulate. Adequate high-frequency response, sharp transient response.

Dull: See dark.

Edgy: Too much high frequencies. Trebly. Harmonics are too strong relative to the fundamentals. Distorted, having unwanted harmonics that add an edge or raspiness.

Fat: See Full and Warm. Or, spatially diffuse - a sound is panned to one channel, delayed, and then the delayed sound is panned to the other channel. Or, slightly distorted with analog tape distortion or tube distortion.

Full: Strong fundamentals relative to harmonics. Good low-frequency response, not necessarily extended, but with adequate level around 100 to 300 Hz. Male voices are full around 125 Hz; female voices and violins are full around 250 Hz; sax is full around 250 to 400 Hz. Opposite of thin.

Gentle: Opposite of edgy. The harmonics - highs and upper mids - are not exaggerated, or may even be weak.

Grainy: The music sounds like it is segmented into little grains, rather than flowing in one continuous piece. Not liquid or fluid. Suffering from harmonic or I.M. distortion. Some early A/D converters sounded grainy, as do current ones of inferior design. Powdery is finer than grainy.

Grungy: Lots of harmonic or I.M. distortion.

Hard: Too much upper midrange, usually around 3 kHz. Or, good transient response, as if the sound is hitting you hard.

Harsh: Too much upper midrange. Peaks in the frequency response between 2 and 6 kHz. Or, excessive phase shift in a digital recorder's lowpass filter.

Honky: Like cupping your hands around your mouth. A bump in the response around 500 to 700 Hz.
Mellow: Reduced high frequencies, not edgy.

Muddy: Not clear. Weak harmonics, smeared time response, I.M. distortion.

Muffled: Sounds like it is covered with a blanket. Weak highs or weak upper mids.

Nasal: Honky, a bump in the response around 600 Hz.

Piercing: Strident, hard on the ears, screechy. Having sharp, narrow peaks in the response around 3 to 10 kHz.

Presence: A sense that the instrument in present in the listening room. Synonyms are edge, punch, detail, closeness and clarity. Adequate or emphasized response around 5 kHz for most instruments, or around 2 to 5 kHz for kick drum and bass.

Puffy: A bump in the response around 500 Hz.

Punchy: Good reproduction of dynamics. Good transient response, with strong impact. Sometimes a bump around 5 kHz or 200 Hz.

Rich: See Full. Also, having euphonic distortion made of even-order harmonics.

Round: High-frequency rolloff or dip. Not edgy.

Sibilant: "Essy" Exaggerated "s" and "sh" sounds in singing, caused by a rise in the response around 6 to 10 kHz.

Sizzly: See Sibilant. Also, too much highs on cymbals.

Smeared: Lacking detail. Poor transient response, too much leakage between microphones. Poorly focused images.

Smooth: Easy on the ears, not harsh. Flat frequency response, especially in the midrange. Lack of peaks and dips in the response.

Spacious: Conveying a sense of space, ambiance, or room around the instruments. Stereo reverb. Early reflections.

Steely: Emphasized upper mids around 3 to 6 kHz. Peaky, nonflat high-frequency response. See Harsh, Edgy.

Strident: See Harsh, Edgy.

Sweet: Not strident or piercing. Delicate. Flat high-frequency response, low distortion. Lack of peaks in the response. Highs are extended to 15 or 20 kHz, but they are not bumped up. Often used when referring to cymbals, percussion, strings, and sibilant sounds.

Thin: Fundamentals are weak relative to harmonics.

Tight: Good low-frequency transient response and detail.

Tinny: Narrowband, weak lows, peaky mids. The music sounds like it is coming through a telephone or tin can.

Transparent: Easy to hear into the music, detailed, clear, not muddy. Wide flat frequency response, sharp time response, very low distortion and noise.

Tubby: Having low-frequency resonances as if you're singing in a bathtub. See bloated.

Veiled: Like a silk veil is over the speakers. Slight noise or distortion or slightly weak high frequencies. Not transparent.

Warm: Good bass, adequate low frequencies, adequate fundamentals relative to harmonics. Not thin. Also excessive bass or midbass. Also, pleasantly spacious, with adequate reverberation at low frequencies. Also see Rich, Round. Warm highs means sweet highs.

Weighty: Good low-frequency response below about 50 Hz. Suggesting an object of great weight or power, like a diesel locomotive.





Originally posted my Nigel 1977
http://forums.trinituner.com/forums/viewtopic.php?t=204106&highlight=

[Soundstream_626]

http://www.nousaine.com/nousaine_tech_articles.html

[3stagevtec]

An excellent read on Woofer Speed by Adire Audio

http://www.adireaudio.com/Files/WooferSpeed.pdf

[3stagevtec]

The Big 3

The big 3 is upgrading 3 specific sets of wires that will greatly help with current flow in your vehicle.. Usually 4 or 2 gauge wire will be sufficient because of the short distances.. but you will often see it done in zero gauge wire for the very high end installs..

1) Engine Block to Battery Negative
2) Vehicle Chassis to Battery Negative
3) Alternator Output lead to battery Positive.

The most important upgrade out of the three is engine block to battery negative, as the true ground point in your vehicle is actually alternator's casing!

and as the alternator is bolted to the engine, you must properly connect your engine block to the vehicle's chassis...

extra reading

http://www.the12volt.com/installbay/forum_posts.asp~TID~73496~PN~1

too lazy to read?? well..

[3stagevtec]

SPL ENCLOSURE GUIDELINES

Part two of our enclosure-building series.

Have you ever wondered what it takes to be a big time competitor in the SPL arena, posting the big numbers -- you know, the ear-shattering 170-plus decibels? If you know something about physics, you may think you have it figured out. You would know that rapidly compressing and rarifying the air can change the pressure within an airtight environment, in this case the cab of the vehicle. And if you were so inclined, you would likely apply this knowledge in SPL competitions by searching for the "golden subwoofer" with high power handling potential and the longest excursion (so that as much air as possible could be moved). Once you found the "golden subwoofer" you would measure the vehicle to see just how many of these puppies you could stuff into the interior. And, since you want to compress and rarify the air, it would make sense to have a sealed chamber, where the front and rear wave of the speaker could not interact. All the while you would want to minimize the volume of the chamber (cab of the vehicle) so there would be less air to move. In the end, you wind up with a sealed enclosure.

Stepping into the SPL lanes will cause most physicists to become confused. Immediately, they'll ask, "Where are all of the sealed enclosures?" You see, the majority of warped and extreme competitors taking top honors in SPL competitions today use ported enclosures, not sealed. Why? I think it is safe to say that many of these competitors don't actually know themselves, they just learn from trial and error. Cut and try.

So where does the answer to high SPL lie? The physicist is actually correct in theory to recommend a sealed enclosure. However, there is one small problem: subwoofers. Current subwoofer designs cannot move enough air due to excursion limitations. On the other hand, ported enclosures are slightly less dependent on excursion. So how are they producing such high output? There are a couple of reasons for this. The first is the design of the enclosure. Ported enclosures can be tailored to have a large gain in response over a small bandwidth by simple alterations of the enclosure volume and port dimensions. These simple alterations can produce a peak from 10 to 15dB, raising the sensitivity of a normal speaker within the small bandwidth over the 100dB mark. The second reason for such high output is the alignment of the front and rear sound waves based on a specific vehicle. This is the portion of the design that eludes most competitors.

SPL Waveform
In Box Basics, Part 1 (January 2002), I covered the differences amongst a variety of today's popular enclosure styles. One particular enclosure, the ported, is the basis for the SPL waveform theory I am about to go over. But, before I get into thick of things, I would like to recap the design principles of a ported enclosure.



Ported enclosures are distinguished by a vent or duct in the structure. This vent allows the rear sound wave of the woofer to interact with the front sound wave. The coupling of a vent to the air inside the enclosure reinforces the low-frequency response of the subwoofer system and can greatly increase the efficiency. By changing either the length or surface area of the port, the resistance to motion of the column of air within the port changes its resonant characteristics, thus causing the tuning frequency of the enclosure to change.

These traits are very important to the design of an SPL enclosure. However, the key element of this design is the rear sound wave interaction, better yet, the coupling with the front wave of the speaker. These two waveforms are naturally out of phase with each other (figure 1) and can cancel one another out in a free-air setting. The idea is to get the rear sound wave in phase with the front sound wave. This can be accomplished by the design of the enclosure and will yield a significant increase in output that is ideal for the SPL lanes (figure 2).



Unlike a normal ported enclosure that is built for a broad range of frequencies, an SPL enclosure is designed to be more "frequency specific". In other words, sound quality is not a priority in the design of these earth-shaking mutants. Rather, the concentration will be to produce a one-hit (frequency) wonder. This will likely require a substantially sized enclosure and the port or vent to be commonly larger than the Sd (cone area) of the subwoofer.

The Design Process
The first step in designing an SPL enclosure is finding the frequency that will work best in your vehicle. But how do you know what is the correct frequency to use? This is not as complicated as it may seem.

A single frequency sound wave will take the form of a sine wave. This sound wave can be measured or equated by using a simple formula. Sound waves are normally measured in feet, but since we are working in the small confinements of an automobile, it will be more practical to show this in inches. This means that you must first start by converting the speed of sound, 1130 feet/second, into inches. This can be accomplished by simply multiplying 1130 x 12 for a result of 13560 inches/second (figure 3).



Now let's start the design of the enclosure within the vehicle. Using the rules for dB Drag Racing (Super Street and Extreme competition), we have the following: "All loudspeaker enclosures, and/or baffle boards, with the exception of those mounted in the kick panels or doors, shall be located behind an imaginary plane that stretches from the trailing edge of the driver's door to the trailing edge of the passenger door". With this in mind, placement of the enclosure will likely be positioned slightly behind the door jam, as shown in figure 2.


In figure 2, there are four lines marked A, B, C, and D. Since line A is technically in-phase, we will start with this. Line A relates to the measurement from the speaker cone to the point of reference at the dash where the microphone is placed during competition. Let's use a nice round number for this length, say 50". Knowing this we can now calculate the frequency, employing the equation in figure 4a. At 50", the equation tells us that the full waveform at the dash will be 271Hz. Unfortunately, this will not fly in dB Drag Racing where the rules state that the frequency used in the competition must be 80Hz or below. So how do we get the frequency from 271Hz below the 80Hz mark? If we break down a sound wave into four sections, 90/180/270/360 degrees, it is possible to lower our peak frequency. In this case using a 1/4 of the waveform, 90 degrees, our peak frequency will lower to a very usable 68Hz (see figure 4b). Perfect!



Now that we know that 68Hz is going to be our peak frequency, it is time to hit the computer for our enclosure volume and port dimensions. There are several enclosure programs available that can perform this task. LEAP by LinearX is far superior to most because it takes into consideration the behavior of a loudspeaker at high power levels (see p. 72). But others such as Termpro and BassBox Pro do an excellent job as well. The goal of designing the enclosure is to create the loudest peak possible near the 1/4 wave frequency (see figure 5). Be prepared, the design of the enclosure may take some time; this is basically trial and error to find the correct volume, and an estimated port area and length.



Once the enclosure volume and port are decided, the actual design must take place, the most integral part of the process; so we are certainly not out of the woods yet. Figure 6 displays both the front and rear wave and how they should form in the vehicle. Reverting back to figure 1 for a second, the front of speaker is noted as 0 degrees and the rear is 180 degrees. This is the same as in Figure 6 (noted by the yellow and green lines). The idea is to align the rear wave with the front wave. This means that the front wave starts at 0 degrees and reaches the reference point at the dash at 90 degrees. On the flipside, the rear wave of the speaker starts at 180 degrees and reaches the dash in-phase with the front wave at 90 degrees. This means that the rear wave of the speaker must be exactly three times the length of the front. In equation form: 3A = B + C + D (refer to figure 2).



There is a good chance that you may be using more than one subwoofer in your competition vehicle, so there is one other issue you need to consider. By now you understand how to control the sound waves produced by the subwoofer. When multiple subs are used, each needs to be on the same wavelength, so to speak (playing the same frequency). This means that each sub needs to be the same distance from the microphone as the next. This also means that the rear sound wave has to be the same distance. Keep in mind that the enclosure volume and port must stay the same per subwoofer, but the dimensions of the enclosure may change so that the rear wave remains in-phase with the front. Now you are set to start building the enclosure -- but be sure to leave yourself room for adjustments, mainly with the port length. Computer programs will give you a good base to work off of, but it's not always exact.

There are several other aspects to the design of an SPL competition vehicle, such as altering the interior volume and strengthening the enclosure. The interior volume should generally be more than or equal to that of the enclosure; otherwise the peak frequency may change and alter the output of your design. The strength of the enclosure matters greatly to reduce harmful resonance. Any structural support should be done on the outside of the enclosure to assure that there are no additional reflective surfaces in the enclosure that may add cancellation.

Hopefully I have provided you with an understanding of what is happening in some of these competing enclosures on wheels. Controlling the waveform inside a vehicle can have substantial benefits in terms of SPL, and coupling the rear wave of the speaker with that of the front wave substantially increases volume, which is advantageous when you are reaching for high scores.

The speed of sound can vary depending on the temperature of the air. As an example, at 60 degrees (F), the quarter wave of a 50Hz sound wave will form a complete wave in 67 inches, whereas the same frequency (50Hz) needs 69.13 inches at 90 degrees (F). A drastic change in temperature may vary the peak frequency in your vehicle by 1-3Hz.

Originally Posted By Fuzz 174

http://forums.trinituner.com/forums/viewtopic.php?t=105718&highlight=

http://www.caraudiomag.com/technical/0203cae_audio_speakers_basics/index.html

[fuzz_174]

i remember that article

Good post!

[Chiney]

yeh dread.. GREAT READ!

[3stagevtec]

The Relationship Between Xmax and SPL

This is always an interesting and controversial topic. Every couple of weeks, a debate rages regarding the relevance of high Xmax and whether it is truly valuable to achieving SPL scores. Perhaps the greatest argument is that Digital Designs Audio drivers, who have a very impressive track record in SPL competition, have been routinely tested to show below average Xmax numbers. How is it possible that a driver with limited linear excursion can still be amongst the loudest? The answer is simple and complex all at once: Xmax is relevant to SPL and it's not. Now that I've confused you, let's proceed.

I'll touch on how a speaker makes sound and how it's interpreted at a later time, but let's skip to some ground works. Acceleration is a critical component of creating SPL. The higher the rate of acceleration, the more pressure that can be created. Let's figure out how to get there.

If you've been through any high school physics classes, you're probably very familiar with this equation.

F=m*a

Hey, that looks like Newton's Second Law of Motion. In short, it states that the net force of an object is equal to the product of it's mass and it's rate of acceleration. Of course, we can re-write the simple formula to better suit our needs.

F/m = a

After our spinning, the formula reads that the rate of acceleration is equal to the net force of an object divided by it's mass. Let's apply this to speakers for a moment, shall we? The force of an speaker is determined by the two factors:
1. BL - the combination of the magnetic field strength (B ) and the length of the voice coil in the gap (L)
2. i - the level of input current

Taking that information and our above equation, we can easily translate this to a speaker relevant equation.

(BL* i)/m = a

Let's make some logical conclusions from this formula.

1. Increasing the magnetic field strength (B ) or the length of the voice coil in the gap (L) will increase the rate of acceleration
2. Increasing the level of input current (i) will increase the rate of acceleration
3. Increasing the mass of the driver will decrease the rate of acceleration

Naturally, the inverse of these conclusions holds true as well. For example, if you decrease the moving mass of the driver, the rate of acceleration will increase. Simple stuff, me thinks. Now we have our foundation for understanding why Xmax is and is not relevant to SPL.

We know what we want to have a really loud driver, don't we? Huge BL, ability to take a lot of power, with extremely low moving mass. When looking at thiele/small parameters, we are looking for something with a high BL^2/Re, high power handling, and low Mms. It's odd that Xmax isn't factored into that equation, don't you think? Ahh, but it is, in a sense.

Once we apply current to the voice coil, it moves. Based on the Understanding Power Compression thread, we know that as the voice coil moves out of the gap, BL decreases. It stands to reason that as the voice coil moves out of the gap, BL decreases, and based on our previous conclusions, so does the rate of acceleration! In this sense, high Xmax is a good thing because it means the driver is capable of moving further without an alarming decrease in BL. In this sense, high Xmax is a great thing. A driver that can move great distances while keeping BL very linear can make for a very good, very loud driver. This is handy for competitions like Bass Race, where everyday music is played for longer durations.

With that said, there is another aspect of SPL competitions where high Xmax may not matter so much. In DBDrag style competition, high Xmax is not always critical. Typically, a competitor plays a short burst sine wave near the resonant frequency of the port(s) used in their enclosure. This excites the air mass in the port, causing it to become the primary source of our pressure. Meanwhile, the driver that is exciting the air mass is relatively stationary; it is not excurting itself very much at all. If your driver is only moving +/- 2mm, what is the difference in BL between a driver with 16mm of Xmax and a driver with 100mm of Xmax? Not much at all.

There is one more important consideration in the "high Xmax vs. SPL" equation. Again, looking back at that original equation, we know that high moving mass decreases our rate of acceleration. Let's pretend I'm engineering a driver for a client who wants high Xmax using conventional designs (more on this another day). How do I do so? Quite simple: I add length to the voice coil. There is, however, a caveat to adding length to your voice coil: more wire (be it copper, aluminum, etc) adds mass to the driver as well. This is not a good thing from an SPL standpoint.

As we can clearly see, high Xmax and SPL are not necessarily mutually exclusive; in fact, sometimes they go hand in hand. At the same time, some situations call for very little Xmax. This is why companies like Fi Car Audio deserve more credit than they receive: there is no one answer for every question, but we'll allow you to customize our answer to suit your question.

The point comes back to a daily engineering focal point: where can I afford to make sacrifices for the application? And that ultimately brings us to Newton's Third Law:

For every action, there is an equal and opposite reaction.

Cheers!


Article from Neil on the SSA Forums
http://www.soundsolutionsaudio.com/forum/index.php?/topic/8375-the-relationship-between-xmax-and-spl/

[a little louder]

Air Gap
In a speaker's motor section, the space between the top plate and the pole piece. This is where the magnetic flux field is concentrated and where the voice coil interacts with it.

Amperes
Ampere is a unit measurement of current of electrical energy equal to one coulomb of charge per second. Most DC applications refer to positive current - current which flows from a positive potential to a more negative potential, with respect to a reference point which is designated as zero or neutral potential (usually ground). The electrons in a circuit flow in the opposite direction as the current itself. Ampere is commonly abbreviated as "amp", not to be confused with amplifiers, of course, which are also commonly abbreviated "amp". In computation, the abbreviation for amperes is commonly, "I".

Amplification Classes
All sound is a sinosoidial waveform. It has alternating peaks and valleys. The center point of each wave is the zero, or switching point that separates the positive (top) from the negative (bottom) portion of each wave. When a tube or transistor amplifier operates in Class A, the output tubes or transistors amplify the entire waveform without splitting it into positive and negative halves. In Class AB, used in the overwhelming majority of amplifier designs, the signal is split into two halves, positive and negative, and each half is sent to a tube or transistor circuit for amplification. Both sides work in tandem, and the two halves are recombined at the output section to reconstruct the whole signal. This technique increases the amount of power that can be applied, but increases distortion. Class A amps usually provide lower, often imperceptable distortion, but at the expense of reduced power output.Class D or High Current operation is essentially rapid switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Theoretically, since the output devices are either completely on or completely off they do not dissipate any power. If a device is on there is a large amount of current flowing through it, but all the voltage is across the load, so the power dissipated by the device is zero; and when the device is off, the voltage is large, but the current is zero. Consequently, class D operation (often, but not necessarrily digital) is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product yet to be made; meanwhile designs do exist with efficiencies approaching 90%. This is a design that is increasimgly popular for use in bass systems, where maximum power is necessary, and slightly elevated levels of distortion are easily tolerated.
Amplifier A device, either a single stage or a large scale circuit with mutiple stages for creating gain, ie. making small signals larger.

Back Plate
The part of the woofers metal Basket or frame on which the Magnet structure is mounted.

Baffle
A flat panel that divides the front and rear sound waves produced by a woofer. Sometimes baffle is used to mean an enclosure or the front panel on which the speaker is mounted.

Bandpass (box or enclosure)
An enclosure that is specifically tuned to give maximum energy to a very limited range of frequencies, usually the lowest. In this arrangement, the woofers are fully enclosed in the box with the sound pressure being vented through one or more ports.
Bandpass filter A filter that has a finite passband, neither of the cutoff frequencies being zero or infinite. The bandpass frequencies are normally associated with frequencies that define the half power points, i.e. the -3 dB points. In multi-driver speaker systems, the Midrange driver may be fed by a bandpass filter.

Bandpass Gain
The increase (or decrease) in efficiency of loudspeakers, due to the enclosure size and tuning. This is measured by the midband sensitivity of the speaker as a whole.

Basket
The metal frame structure of a standard dynamic loudspeaker. In larger, heavier speakers, this may be made of cast metal for extra strength and rigidity. All the other elements of the speaker are mounted on this structure.

Bass
The portion of the audible sound spectrum that contains the lowest frequencies. These frequencies have the longest wavelength and require considerably greater electrical power to render them at their original strength. In a good modern speaker system, the bass portion of the response curve extends from as high as 500 hertz, down to 20 Hz.

Bass Boost/Enhancer Circuit
An active low pass amplifier section added to some receivers, equalizers, and amplifiers that allows as much as an 18 decibel boost to be applied to an audio signal in the low frequency 35 to 90 Hertz range.

Bass Reflex (box or enclosure)
A speaker box design that makes use of a port or Passive Radiator which allows the energy derived from the motion of the back of speaker cone to be redirected in such a way as to reinforce the front radiation. This smooths and extends the low frequency response, but the effect is sharply Rolled Off on the low end, as the port signal goes back out of phase with the front. The overall effect of this is to tune the bass response to a particular point on the lower end of the spectrum, below which it rolls off sharply.

Bridged Power
Bridging an amplifier, combines the power output of two channels into one channel. Bridging allows the amplifier to drive one speaker with more power than the amp could produce for two speakers. Because of this high power output, bridging is the best way to drive a single subwoofer.

Capacitor (Power audio)
Power stabilizing capacitors store the necessary power amplifiers need to punch larger bass notes while limiting clipping. They store energy during intervals when it is not required, which is most of the time, and release it when demand exceeds what is available from the car's power system. The amount of capacitance to be used is half (.5) farad per 500 watts of available RMS power. Capacitors are not used with amplifiers that supply less than 300 watts RMS in total.

Component System
This term is used in relation to speaker systems, to indicate a system in which separate mounting arrangements are provided for each component of the system. In a typical car system you might see a woofer in a box in the rear, midranges at the side and tweeters mounted on the dash panel. This compares to the typical integrated speaker enclosure in which all the Drivers are mounted in the same box.
Compression Driver

Compression drivers are usually dynamic; that is, with a magnet and interacting coil arrangement, and a small diaphragm as the main transducer. These are the motor parts, also known as the driver, of a compression horn tweeter or compression horn general-purpose speaker, such as those used for Public Address (PA) purposes. These drivers are usually coupled to the throat of an exponential horn. Such an arrangement enables this type of tweeter to have very high directional characteristics, which allows them to be especially effective in situations requiring a very wide sound field. In typical home and car stereo near-field applications, large horns can be a bit too narrowly directional to be practical. For this reason, compression horn systems are usually found only in special purpose speakers used in mid and wide field applications such as PA systems or the sound systems installed in large theaters. However, some specialized horns have small apertures and very shallow horns, and can be quite suitable for close spaces.

Compressor
A type of dynamic range processor which reduces the gain of audio signals which are over an adjustable 'threshold' level, therefore reducing the dynamic range. Generally allows the operator control over threshold, ratio, attack and release times. Both analogue and digital types are available.

Crossover
A device or passive circuit used in systems with separate tweeter and/or midrange Drivers. It Rolls Off frequencies above and below certain points in the range, to allow the sound to be tailored for the specific driver to which it is sent. Most speakers have crossovers that consist of passive elements such as capacitors, coils, and resistors to separate the various frequencies. In a bi-amped or multi-amped system, the crossover is an active device that feeds the various frequency bands to the inputs of the amplifiers that operate the individual drivers.

Crossover Frequencies
The frequencies at which a passive or electronic crossover network divides the audio signals, which are then routed to the appropriate amplifiers or speakers.

Cutoff Frequency Filters
The frequency at which a signal falls off by 3 dB (the half power point) from it's maximum value. Also referred to as the -3 dB points, or the corner frequencies.

Decibel or dB (see also Efficiency and Sensitivity)
One tenth of a Bel. This is a measurement of the comparative strength of two powers, and can be applied when measuring any signal in the audio, video, and electromagnetic spectrum. If two powers differ by one Bel, there is a difference of 10 times the power. If comparing amplifiers, where one is rated at 10 watts while the other is 100 watts, then we have a difference of 10 decibels, or one Bel. Decibels should be understood as ratios, not fixed quantities. smallest difference in volume that can be heard by the average person. The term is derived as an honor to Alexander Graham Bell, who invented the telephone, and did much of the preliminary work in the modern science of acoustics.

Diaphragm
This term describes the sound-producing element in a tweeter, or Horn. This is the surface that produces the sound you actually hear. The motor that drives it can be any of several technologies including Piezo, conventional dynamic, or ribbon types. Diaphragms do not produce low and low midrange frequencies well, so they are not usually found in that application.

Die Cast (basket)
A type of speaker basket or frame that is cast as a single piece of relatively thick, rigid metal. This contrasts with a Stamped frame that is shaped by pressure, much like a car body fender. Cast metal is heavier and more rigid, and thus less likely to "ring" at certain frequencies, and will hold its shape somewhat longer against the pull of gravity. This is mainly advantageous in the larger woofers of 12" or greater. Smaller drivers will likely not benefit perceptibly from being cast.

Dispersion
The extent to which a sound emitter yields acoustic radiation over a given area. This is a particular concern in tweeters and midranges whose portion of the audio spectrum has a much more directional character than woofers. Many Horn tweeters, while very energetic, have a more limited area of dispersion within which their effect can be fully perceived. Generally, Dome tweeters can be heard over a much wider area, all other factors being equal. But each particular example must be assessed individually for this factor. Some radiator designs are better than others.

Displacement
The measurement of cubic volume that an item (such as a speaker or port) takes away from the internal volume of an enclosure. When designing an enclosure, this figure must be added to the enclosure volume .

Distortion
Any departure from a true and accurate reproduction of the original waveform. It can include Noise, Clipping Distortion, Harmonic, and Intermodulation Distortion. These last two forms are fairly common in loudspeaker reproduction and can be reduced but not entirely eliminated in the existing technology. It would be fair to say that modern amplifier design fairly eliminates nearly all forms of inherent perceived distortion, leaving only that caused by inappropriate user settings and overloading. Distortion is the name given to anything that alters a pure input signal in any way other than changing its size. The most common forms of distortion are unwanted components or artifacts added to the original signal, including random and hum-related noise. Distortion measures a system's linearity - or nonlinearity. Anything unwanted added to the input signal changes its shape (skews, flattens, spikes, alters symmetry or asymmetry). A spectral analysis of the output shows these unwanted components. If a circuit is perfect, it does not add distortion of any kind. The spectrum of the output shows only the original signal - nothing else - no added components, no added noise - nothing but the original signal.

Driver
An alternate term for: speaker, transducer, or radiator. Properly speaking, the term speaker should refer to an entire sound producing system with whatever combination of woofer, midrange and tweeter; in whatever enclosure type it is housed.

Driver Volume The amount of enclosure airspace that is displaced by the speaker itself.

DSP (digital signal processing)
A technology for signal processing that combines algorithms and fast number-crunching digital hardware, and is capable of high-performance and flexibility.

Dual Channel or Dual Voice Coil (speaker)
A woofer with two voice coils mounted to a common cone, which can be connected to separate amplifiers, to produce a common bass output. Since bass has a non-directional character, this still permits the optimum reproduction of the stereo image via other speakers. Care should be taken in making connection, to observe proper polarities, however. Failure to do so can result in the quick extinction of the Driver if the amplifiers are pulling the cone in different directions at once.

Dual-Cone
Many factory installed auto speakers are of the dual cone type. Sometimes also referred to as a "full-range" speaker, it uses an inexpensive, efficient design. The small "whizzer" cone in the center of the woofer reproduces high frequencies, but not with the dispersion, range, or intensity of a separate tweeter.

Dynamic range
The ratio of the loudest (undistorted) signal to that of the quietest (discernible) signal in a unit or system as expressed in decibels (dB). Dynamic range is another way of stating the maximum S/N ratio. With reference to signal processing equipment, the maximum output signal is restricted by the size of the power supplies, i.e., it cannot swing more voltage than is available. While the minimum output signal is determined by the noise floor of the unit, i.e., it cannot put out a discernible signal smaller than the noise. Professional-grade analog signal processing equipment can output maximum levels of +26 dBu, with the best noise floors being down around -94 dBu. This gives a maximum dynamic range of 120 dB - pretty impressive numbers, which coincide nicely with the 120 dB dynamic range of normal human hearing (from just audible to uncomfortably loud).

Dynamic Range Suppression
A signal compression technique which raises the level of lower passages without affecting overall volume. Especially useful with high noise levels, such as a moving vehicle.

Efficiency (see Sensitivity)
The ability of an audio system to convert electrical energy (watts) into mechanical energy (Decibels of acoustical energy). This ratio is usually given as the amount of energy measured in Decibels at a distance of one meter from the input of one watt of electrical energy. In most speakers, the greater the efficiency rating, the louder the unit will play in response to the same setting of the volume control, in comparison to less efficient types. The overall efficiency for most speakers systems is under 20 percent. Typical speakers can be rated at anywhere from 85 to 110 dB. Keep in mind, of course, that efficiency is only one parameter of a speaker's overall quality.

Electrolytic Capacitor
A polarized capacitor with a negative and a positive terminal that is commonly used for DC power filtration and energy storage. As with all capacitors, the dielectic insulator separates two plates and holds a charge. In this case the dielectric is a form of chemical electrolyte that is polarized. Smaller types are mesured in microfarads while the large ones used for amplifier stabilization are measured in farads. Values in the range of .5 to 3 farads are typical for use with car audio amplifiers.

Enclosure, or Box
A cabinet in which the various Drivers are housed. This arrangement is absolutely essential if bass response is desired from the woofer, which by itself in the open air, will produce very little low frequency response. This is so because of an effect called phase cancellation. This means that the sound wave coming from the back of the speaker at low frequencies is identical in form and intensity to the one coming from the front of the cone. When they meet, as in the open air, they are exactly 180 degrees out of phase and thus cancel each other out. An enclosure either prevents this from occurring or modifies the interaction so that the backwave actually reinforces the front wave. Tweeters and midranges are less severly effected by the phase cancellation effects, and are not in need of enclosures.

ESP
Electronic Shock Protection.
An electronic circuit that stores the audio data stream from a CD or MD in a memory buffer. If the laser pick-up mistracks, audio still flows from the buffer preventing an interruption.

Flush (mounting)
Mounting a speaker in such a way that the speaker and its Grill do not protrude above the surrounding surface. Usually, this means mounting it at the back of the baffle board (the board the speaker is mounted on).

Former
The cylindrical portion of a speaker's voice coil section. A wire is wound around this cylinder to form a coil such that when current interacts with the magnetic field it produces a pumping motion that alternatively compresses and rarifies air, and creates the velocity for such air masses to reach our ears as sound.

Frequency Response
The range of frequencies that a speaker will reproduce (lowest frequency to the highest). While the optimal normal is 20 - 20,000 Hz (Hertz), the range of human hearing for individuals is often much more restricted. A good full-range speaker system however, will reproduce as much of this range as possible in order to cover all variations. Individual Drivers are limited to reproducing only that part of the spectrum for which they were made, so their response will be limited, but still a necessary point to consider when designing a complete sound system.

Gain
An increase in volume or amplitude, usually measured in dB.

Grill
A barrier meant to prevent damage to the Driver that it covers, or that creates a more attractive appearance.

Ground
A term that describes anything having an electrical potential of zero relative to other points in a circuit. Most modern vehicles are designed around a negative ground system, with the metal frame being the vehicle's ground.

Ground Loop
The term given to the condition that occurs when a voltage potential exists between two separate ground points.

Heat Dissipation
The function of transfering heat away from a component into the air to prevent damage to the output section of an amplifier or the voice coil of a speaker.

Heat Sink
Parts of an amplifier, typically heavy metal "fins," and a section of the frame of the speaker used to conduct and radiate heat away from the ponit of electrical consumption, or motor assembly.

Hertz
The measurement of frequency. One hertz is equal to one cycle per second, or the complete cycle of an alternating (AC) waveform. Higher frequencies are measured in kilohertz, (thousands of cycles per second) Megahertz, (millions of cycles per second), etc.

Impedance
The totality measured in Ohms of all electrical opposition to current flow: resistance, reactance, capacitance, as well as all mechanical factors inhibiting the completion of energy transfer in a contained system. In practical terms, this means that most Drivers are assigned a certain nominal impedance based on their DC voice coil resistance and mechanical stiffness. For car audio this is usually 4 ohms; for home stereo, 8 ohms is the standard.

Input Sensitivity
is the SPL (sound pressure level) a speaker will produce given one watt of power as measured from one meter away given a typical input frequency (usually 1kHz unless otherwise noted on the speaker). Typical sensitivities for car audio speakers are around 90dB/Wm. Some subwoofers and piezo horns claim over 100dB/Wm. However, some manufacturers do not use true 1W tests, especially on low impedance subwoofers. Rather, they use a constant voltage test which produces more impressive sensitivity ratings.

Input Voltage
The power voltage provided to an amplifier. While most cars can be expect to reliably produce 12 volts, amplifiers are sometimes measured at higher voltages; up to 15 volts. In this way, higher power can be developed, albeit at the expense of longevity. It is a practice that allows higher power figures to be claimed.

Load
The resistance or impedance to which energy is being supplied. In amplifiers, the speaker or speakers connected to the output of the amplifier.

Low Frequency
Refers to radio frequencies within the 30-300 kHz band. In audio it usually refers to frequencies in the 20-160 Hz band.

Low Pass Filter
A network of components which attenuate all frequencies above a predetermined frequency selected by the designer. Frequencies below cut-off are passed without any effect.

Magnet Boot
A rubber or plastic cover for the magnet housing for protection or appearance, mostly the latter.

Magnet/Magnet Structure
A combination of magnetic material and connected field concentrators that creates the magnetic field within which the voice coil interacts to produce sound. Magnetic materials have changed greatly over the years to produce much higher concentrations of magnetic fields (rated in gauss) with lighter and smaller volumes of material. In marketing speakers, a great deal of hype is often applied to the question of magnet weight. But many of these claims should be treated with skepticism. With greater and greater concentrations of gauss fields being developed from ever lighter and smaller mass metallurgical materials, the only good measure of adequate power handling is the manufacturer's RMS Wattage rating. Hefty magnets may look impressive, but while capable,they are no longer an essential index to a speaker's power capacity.

Midrange
A Driver that is usually much smaller than a woofer, but with a surface area greater than the typical tweeter. It reproduces the mid frequency range from approximately 300 to 5000 Hertz. This optimum range can vary considerably from one driver to the next, thus giving the system designer more flexibility in choosing Crossover points for the other drivers.

Mono (monaural)
The operation of an amplifier in one channel for both input and output. Can refer to an amplifier with only one channel of amplification or operating in bridged mode. For low frequency amplification applications, it provides better phase coherence and less distortion than stereo operation.

MOSFET (Metal Oxide Semiconductor Field Effect Transistor)
A type of large output transistor used in the final stages of many power amplifiers, and commonly found in most car and home amplifiers today.

MOSFET Power Supply
A power supply that employs MOSFET transistors to convert DC to AC. Offers superior thermal stability and more accurate switching.

Motor Structure
In speakers, the complete sound generator or transducer that converts incoming electrical signals to mechanical/acoustic energy or sound. In a dynamic Driver, this includes the magnet, its directive field concentrators or Pole Pieces, and the voice coil that interacts with them.

Ohm
The measurement of electrical resistance and system impedance. It is a measure of the degree to which electrons are limited in both velocity and quantity in passing through a circuit. In Impedance measurements, this takes into account, the mechanical resistance inherent in the motion of transducers. The standard is usually 4 ohms for car audio and 8 ohms for home and commercial audio. Some specialty woofers may be rated at 16 ohms.

Ohm's Law
The mathematical relationship between voltage, current, and resistance. It is named after George Ohm, it's discoverer. Ohm's law states that current volume in a conductor is directly proportional to the voltage flow across it and inversely proportional to its resistance. In general, this means that more voltage will produce more current, if resistance stays the same, but higher resistance will cause current to decrease if voltage stays the same. In mathmatical terms, V = I x R, where V is voltage, I is current, and R is resistance. Ohm's law is a description of electron behavior upon which virtually all understanding of electronics is based.

Output (Audio)
The high level (speaker) or line level (RCA) signals sent from one system component to another, or the high level signal from an amplifier to the system speakers.

Peak Power Handling (MAX)
Peak power handling refers to the amount of power a speaker is estimated to handle during a brief high-intensity musical burst. Since this can vary with both frequency and amplitude, it is a much less accurate way to judge speaker durability and performance than RMS (see RMS).

Pole Piece
The ends or "Poles" of a magnet from which the magnetic lines of force, measured in Gauss, are at the greatest strength. In a typical speaker, this will be at the gap within which the voice coil is located.

Polycarbonate
A polymer based plastic material offering superior resistance against resonance.
Polypropylene A plastic based material used primarily for speaker cones due to its rigidity, damping and resistance against harsh environmental conditions.

Power Handling (continuous or RMS)
A rating of a Driver's ability in optimum conditions to handle a specified amount of audio power (electrical current power) on a constant basis, without damage. This is generally considered to be a conservative and reliable figure to use in judging what types of amplifier power will be most successful with a particular speaker design.
RMS Root Mean Square is a formula that provides a reasonably accurate means of measuring and comparing continuous AC power. The use of this measure is preferred when matching system components, like amplifiers and receivers.

Roll Off
A graduated reduction in the strength of audio output above and below certain specified frequencies.

Sealed (enclosure)
Sometimes known as an Acoustic suspension type, the sealed enclosure is a simple design in which each woofer is mounted in a sealed, airtight box or compartment with a specific internal volume for precisely the woofer being used. The air contained within the box or compartment then acts as a spring that allows more control over the speaker's behavior. Great care must be taken in design, as too small a box will sound "boomy," while too large a box may have hardly any bass at all. This should be remembered when replacing a woofer in such an enclosure. Best results can be expected when using woofers with a QTS between .30 to .90. These speakers offer good control, low Distortion and high power handling.

Sensitivity (Efficiency)
The rating of a loudspeaker that indicates the level of a sound intensity that the speaker produces (in dB) at a distance of one meter when it receives one watt of input power.The Efficiency or Sensitivity rating indicates how effectively a speaker converts electrical power from the amplifier into sound pressure. This is frequently related to larger magnet sizes, larger voice coil diameters, and more compliant suspensions. Optimized enclosures are essential in achieving maximum sensitivity, overall. The higher the Decibel number, the more efficient the speaker and the louder it will play with the same input power. While usually more expensive, an efficient speaker helps maximize the potential of the available power.

Signal processors
Electronic devices which alter sound either to achieve a particular effect or to solve a problem with that sound (e.g. delays, compressors, reverbs, noise gates, equalizers).

Signal To Noise Ratio
A measurement of noise level in a device compared to the level of the signal. Higher numbers signify a greater difference, which is better. In technical terms, it is the ratio, expressed in dB, of signal power at a reference point in a circuit, to the noise information that would exist if the signal were removed (the noise floor). The maximum signal to noise ratio (equivalent to dynamic range) of a given piece of equipment can be seen as a measure of functional fidelity. This ratio is how much absolute noise it produces, compared to the highest signal voltage it can pass without distortion.

Sound Pressure Level (SPL)
An acoustic measurement of sound energy. 1 dB SPL is the smallest increment in sound level to which the average human is sensitive. Theoretically, 0 dB SPL is the threshold of human hearing while approximately 120 dB is the threshold of pain.

Spider
The rear suspension element on the cone of a loudspeaker. All the moving parts of the speaker are suspended by the spider in the rear and the Surround in the front. The spider is so named because of its resemblance to an arachnid, especially in the way in which flexion is obtained in the design of the concentric pleats that allow back and forth motion.

THD
Total harmonic distortion is a measure of the how much a given audio device may distort a signal through the introduction of added harmonics or overtones. These figures are usually given as percentages. THD figures below approximately 1% are inaudible to most people. However, distortion is a cumulative phenomenon, so that if a receiver, equalizer, signal processor, crossover, and amplifier are all rated at "no greater than 1%THD", together, they could produce 5%THD, which may well be noticeable in the perceived sound.

Two-way (car speaker)
Music's high frequencies are reproduced accurately by two-way, or coaxial, designs. These speakers use a separate tweeter to deliver high frequency reproduction that surpasses that of dual-cone "extended range" models with whizzer cones. This tweeter, usually a cone or a Dome, is either on a post or bridge inside the woofer.

Variable LP/HP Filter
Crossover components which provide adjustable cut-off frequencies, and levels.

Vented (enclosure)
A type of speaker system also known as Tuned, Tuned Port, Ported, or Bass Reflex. They are basically Acoustic Suspension enclosures with the addition of a port or opening with a specific length. This allows a portion of the lower range to be coupled to the front wave produced by the woofer, in order to enhance the low frequency response. The portion of the range below the tuned point (Fb) is essentially a Free Air Driver that subjects the unloaded woofer to the possibility of severe, even catastrophic damage if the energy below this point is highly amplified. The best results for a vented speaker come when using woofers with a QTS in the range of .10 to .40.

Voice Coil
The voice coil is the coil of wire fixed to a cylinder at the apex of the loudspeaker cone that interacts with a magnetic field. With the help of other speaker components, the voice coil is the active transducer that converts electrical signals from the amplifier or receiver into mechanical energy, which we hear as sound. The voice coil cylinder is the part of the speaker around which the voice coil is wound. More advanced speakers offer a heat-resistant voice coil to prolong speaker life.

Voltage
Voltage is an electrical charge, or potential difference, between two points, one being of higher relative voltage than the other is. A 1.5-volt 'C' battery has 1.5 volts of difference between the positive and negative terminals, for example. The unit of voltage is called the "volt," named after Allesandro Volta. Voltage can be thought of metaphorically as a pressure, such as water pressure in plumbing, that is available to initiate action or work. It, however, cannot do any work until a circuit is complete so that current (measured in amperes) can flow.

Watts
A measurement of power. In speakers, wattage is a term that indicates power-handling characteristics in dealing with electrical voltage inputs from the amplifier. RMS or continuous power handling is the only accurate basis for comparing the capabilities of Drivers. In determining the proper power input for a speaker, use this measure only. So-called Peak Power handling is often only the manufacturers best guess at the power dissipation point, beyond which the unit will fail.

Woofer (Subwoofer)
The bass and lower midrange sounds are reproduced by the woofer. To operate efficiently, a woofer's cone should be made of material that is stiff, yet lightweight. Cones made of polymers, polypropylene, light metals, or poly mixed with other materials including carbon strands and metals, provide excellent sound, and stand up to the heat, cold and moisture that car speakers face daily. Paper cones treated for moisture resistance also do a good job, and are usually very efficient. For car usage, untreated cones should be avoided.

Xmax
A measure of a speaker cone's maximum Excursion (back and forth motion) in one direction while still maintaining a linear behavior (moving in a straight line with high precision). This factor is measured in inches or millimeters. Xmax is more precisely defined as the width of the voice coil that extends beyond the front plate plus 15%. This relates to how far the speaker can move in either direction without appreciable distortion.

[kurpal_v2]

I gained a DB reading this thread..



Who could help me explaining dB dust?

[3stagevtec]

How to achieve awesome mid bass

I have recently received many questions about mid bass. Instead of making several replies I have opted to make this post. Questions and additions welcome.

This is one of the most complex and misunderstood topics in car audio for the following reasons that I will explain.

1. Phase
You must be able to grasp the concept of sound in the incremental phase domain as well as sound in the frequency domain. I will explain.
2. The cars dimensions
The car itself conflicts with good mid bass response do to various interior dimensions of a typical automobile coinciding with the physical size of sound waves in this frequency range.
3. The misconceptions
The misconception that poor mid bass is due to low amplitude in this range. More won’t help. I will explain.
4. Futile attempts
Many of the attempts people make to increase mid bass response only make it worse including gaining up, expanding crossover pass band, adding more speakers, and placing the mid bass drivers in an enclosure.

The term mid bass can be interpreted many ways. In car audio however this band is pretty much set as the band between 50hz and 250hz. This is due to many reasons that are beyond the scope of this article. What’s important to understand is that in the 50hz-250hz range humans are the very least sensitive to variations in frequency response but we are the most sensitive in this range to changes in phase. As frequency rises above 250hz the opposite becomes true. Humans become less aware of phase response and much more aware of frequency response.

Phase
Phase is the angle measured at a given point on a sound wave.


Here you can see that from where Homer sits the sound wave arrives at his ear at one angle but below you can see that when he changes is position relative to the speaker the angle of the sign wave changes as well.


he can’t hear any difference in the sound. But when you add a second speaker things change.


Now his brain is picking up one sound coming from two different places. His brain knows its coming from two different places partially because the phase angle is not the same. When this happens your brain will red flag this sound information as “invalidâ€

[sMASH]

3stagevtec, like u pick up sumting from me after all (reference to the constructive interference of waves)

[3stagevtec]

http://www.caraudiomag.com/specialfeatures/0111cae_anatomy_power_amplifier/index.html

Anatomy of the Power Amplifier
By Robert Zeff

With the Proliferation of Different Amp Types, Which is the One for You? In the past we had essentially two types of amplifiers to choose from: Class "AB" and class "A". Today we have AB, A, D, G, H, & T, in addition to some that do not have a class name. New technology brought down the size and price while improving performance and efficiency. We'll review the various topologies of the modern amplifier, spending extra time on the aspect of efficiency (as the quest for smaller, more efficient designs have spawned the class D, G, H, & T designs). We'll also try to dispel some of the misconceptions and folklore that seem to surround amp design.

Amplifiers require circuitry for short and thermal protection, fan control, turn on delay, and over voltage protection. In the past we littered the designs with dozens of components to handle these events. Today we can use a single microprocessor to handle all of this in addition to having many more features without additional cost. The microprocessor can monitor the battery voltage, internal voltages, temperature, control volume and crossovers, and drive external displays. These embedded computer chips also allow features like compression and power limiting with little added cost. Of course, what is an amplifier without a power supply? First we'll visit the power supply designs, as every amplifier needs one.

The Power Supply
The purpose of the supply is to convert the auto's battery voltage to a higher voltage. For example, if an amplifier is to produce 100 watts into a 4 ohm speaker, we need 20 volts RMS. This implies that we need about +/-28 volts. (20 volts R.M.S. = 28.28 volts peak). We call that the "rail" voltage. Since the amplifier's output transistors cannot pull all the way up to this rail, we actually need a slightly higher voltage.

The process is to convert the 12 volts DC into AC, feed it to a transformer and convert it back to DC again.

Converting the 12 volt battery voltage to AC is simple, a PWM (pulse width modulator) IC feeds a bank of MOSFETS (MOSFETs are switching transistors perfectly suited for this task).

The 12 volt power is switched at a very high frequency, somewhere between 40 and 150 kHz. Slower switching speeds require a larger transformer, but high speeds have more switching loss. Advanced transformer core materials, faster rectifiers, and clever winding methods have enabled us to utilize very high frequencies. Some of today's better amplifiers have very small power supplies that produce enormous amounts of power.

Regulated Power Supplies
Most early audio amplifiers contained unregulated power supplies. Regulated supplies require very high quality filter capacitors (called "low ESR" capacitors), output chokes, and an optically isolated voltage feedback circuit. Regulation occurs by controlling the switching pulse width from 0 - 100% to compensate for changes in the battery and rail voltage. The same action occurs when the audio level increases. As the amplifier draws more power from the supply, the rail voltage drops. Again, the regulator circuitry senses this drop and responds with an increased pulse width.

The high frequency PWM waveform is rectified (converted to DC) and applied to the output filter choke and capacitors. This output of this circuit is the + and - DC rails that feed the power amplifier.

Unregulated Power Supplies
Unregulated power supplies are less expensive than regulated supplies. They do not require an output choke, voltage sense or isolation circuitry. Because the duty cycle is nearly 100%, capacitor ripple current is much lower in unregulated supplies. Lower ripple current requires less expensive capacitors throughout.

Often we hear that unregulated designs have more "headroom". That means that the amplifier will produce extra power during transients. Most home audio amplifiers employ unregulated power supplies. The power supplies in these amplifiers run at 60 Hz, thus the filter capacitors must be 200-500 times larger than those used in high frequency switchers. The extra capacitance in home audio amplifiers results in extra headroom. Headroom for anything other than very short transients simply doesn't exist in the unregulated designs. The following is an example of specifications for an unregulated vs. regulated amplifiers.

Unregulated designs have a higher supply voltage at low power, causing higher voltage on the output transistors. This reduces the amplifier's efficiency.

Small amplifiers (less than 100 watts) cannot justify the extra cost of the regulation circuitry, so we often see unregulated supplies in these amplifiers.

Pros and Cons of Regulated / Unregulated SuppliesSome designers try to keep their supplies regulated down to battery voltages as low as 9.5 volts. The supply compensates by increasing the current. The following table shows voltage and currents for a 500 watt over-regulated amplifier operating at full power.

The current increases dramatically at the lower voltages. Because of higher currents at the lower voltages, the supply efficiency drops further, requiring even more current.

At higher voltages, the pulse width reduces, causing increased ripple current. This high current creates heat in the filter capacitors and can destroy the capacitor's electrolyte. Some manufacturers do not use capacitors of sufficient quality for this range of regulation. These amplifiers may not perform up to specification just one year after installation. Also, the extra current at low voltages is extra hard on a battery that is already suffering! So, we recommend that amplifiers stay in regulation down to about 11 - 11.5 volts. Any properly working charging system can easily keep the battery voltage well above this.

The Amplifier Section, Class AB and AClass AB and A amplifiers are similar, so we'll discuss both here. Class AB amplifiers have transistors that pull up to the positive rail and transistors that pull down to the negative rail. This corresponds to the action of pushing the speaker cone out and in.

Class AB means that the output transistors do not always have current on them. For example, when the upper transistors are pulling up towards the positive rail (pushing the speaker out), there is no current in the lower transistors. When the output signal swings through zero, towards the negative rail, the output transistor must go through a transition from zero current to a non-zero current. The best analogy that I can think of is driving an old car with too much slop in the steering. As you go from one side of the road's crown to the other, the steering crosses a "dead" zone, and you tend to over-steer. Special temperature compensated bias circuitry reduces this dead zone, known as notch distortion. The figure below shows the output of a class AB amplifier with too little bias and the resulting distortion. Notch distortion increases at higher frequencies and low volume levels. Some modern designs have reduced this type of distortion to very low levels.

Class A means that every transistor is always conducting current. They are very similar to class AB amplifiers, but the bias circuitry is set so that there are very high currents in the output transistors. Because these amplifiers do not have this "dead zone', less feedback is required to achieve low distortion.

A 100 watt amplifier may dissipate nearly 100 watts internally even when there is no audio output. This type of design is impractical in the harsh auto environment. Many class A amplifiers pedaled for the automotive market are not really class A. They are huge power wasters in the home as well.

Input and Driver Stages
The amplifier works this way: A small audio signal is presented to the amplifier's input. Transistors are not linear, which means that the input signal will distort somewhat as it passes through the various amplifier stages. To correct this distortion, a portion of the output is compared with the input. The difference creates a correction signal reducing this distortion. The input stage is a special type, called "differential". It has a + and a - input because it must accept both the audio input and the input from the feedback circuitry. Excess feedback can lower distortion dramatically, but cause instability. Careful design rules must be followed to avoid this instability.

The output of the input stage feeds into the driver stage. The driver stage may use one, two, or three devices. Often this circuitry is referred to "Darlington", or "Triple Darlington". The driver circuit feeds the output stage, which may have two, four, six, or more transistors. The more output transistors, the better. Multiple output devices reduce distortion (requiring less negative feedback) and improve reliability.

Bipolar or MOSFET?
We have seen both MOSFET (Metal Oxide Silicon Field Effect Transistor) and Bipolar transistors used in audio amplifiers. Claims have been made that each is superior. I have seen claims that MOSFETs have a tube ("Valve" for the Brits) sound. This is more folklore. The musicians and their instruments are supposed to have "the sound", not audio equipment! MOSFETs are tougher than Bipolars, and can pull closer to the supply rail. It takes more Bipolar transistors to achieve the same power as a MOSFET, therefore Bipolar amps tend to be more expensive. But, MOSFETs are very non-linear, compared to Bipolars and require much more feedback to achieve reasonable distortion numbers. They are a great choice for bass amps, as low frequency audio is not difficult for a MOSFET. The most expensive car and home amplifiers almost always use Bipolar transistors.

Efficiency
What makes an amplifier get hot? Both the power supply and the power amplifier generate heat. The maximum efficiency of the power supply is nearly 100%. Good power supply designs, with the highest quality components approach 85%. The class AB amplifier efficiency at full power can approach 75%. The total efficiency, including the power supply, can be about 65%. But, efficiency drops at lower power and can typically be under 20%. A class AB amplifier actually runs cooler at full power than it does at half power. Run this amplifier into clipping and it might run even cooler! Where is all this power going? The output transistor is basically a large variable resistor. If the instantaneous output voltage should be 40 volts and the power supply is 100 volts, then 60 volts must be "wasted" in the output transistors. Driving a reactive load (like a speaker) causes the efficiency to drop ever further. This brings us to the other audio classes designed to improve efficiency.

Class D
First, let's dispel another myth: Class D does not stand for digital. The input is converted to a two-state (binary) representation of the audio waveform. That's where the similarity ends. This distinction is important because class D doesn't provide the benefits normally associated with digital components.

That being said, class D designs dramatically improve efficiency. Instead of wasting power in the output transistor, the output is switched at a very high frequency between the positive and negative supply rails. If the output is to be zero, then the waveform is at a 50% duty cycle. If the output is to be a positive voltage, then the duty cycle would be greater than 50%. Because the output devices are either completely turned on (no wasted voltage) or completely turned off, theoretically efficiency is 100%. So the audio input must be converted to a pulse width modulated waveform (PWM). The yellow trace below is the output of the amplifier; the blue trace is the PWM waveform. The blue waveform is fed to an output filter, which results in the yellow output waveform. Notice that the output looks somewhat distorted. All of the switching noise and distortion cannot be removed and the result can be seen here. Because of this process of converting the input signal to PWM and converting back to analog, a good deal of distortion is introduced. Conventional feedback like that used in class AB designs is used in these amplifiers to reduce distortion.

MOSFETs are the only choice for class D designs. Most class D designs are useful only for bass amps as they can not switch fast enough to reproduce high frequencies. Some high quality, full range class D designs exist for pro audio, but they are complex with multi-phased outputs.

Class T
Class T (Tripath) is similar to class D with these exceptions: This class does not use analog feed back like its class D cousin. The feedback is digital and is taken ahead of the output filter, avoiding the phase shift of this filter. Because class D or T amplifier distortion arises from timing errors, the class T amplifier feeds back timing information. The other distinction is that this amplifier uses a digital signal processor to convert the analog input to a PWM signal and process the feedback information. The processor looks at the feedback information and makes timing adjustments. Because the feedback loop does not include the output filter, the class T amplifier is inherently more stable and can operate over the full audio band. Most listeners can not hear the difference between class T and good class AB designs. Both class D and T designs share one problem: they consume extra power at idle. Because the high frequency waveform is present at all times, even when there is no audio present, the amplifiers generate some residual heat. Some of these amplifiers actually turn off in the absence of music, and can be annoying if there is too much delay turning back on.

Class G
Class G improves efficiency in another way: an ordinary class AB amplifier is driven by a multi-rail power supply. A 500 watt amplifier might have three positive rails and three negative rails. The rail voltages might be 70 volts, 50 volts, and 25 volts. As the output of the amplifier moves close to 25 volts, the supply is switched the 50 volt rail. As the output moves close to the 50 volt rail, the supply is switched to the 70 volt rail. These designs are sometimes called "Rail Switchers". This design improves efficiency by reducing the "wasted" voltage on the output transistors. This voltage is the difference between the positive (red) supply and the audio output (blue). Class G can be as efficient as class D or T. While a class G design is more complex, it is based on a class AB amplifier and can have the same clean characteristics as well.

Class H
Class H is similar to class G, except the rail voltage is modulated by the input signal. The power supply rail is always just a bit higher than the output signal, keeping the voltage across the transistors small and the output transistors cool. The modulating power supply rail voltage is created by similar circuitry that you would find in a class D amplifier. In terms of complexity, this type of amplifier could be thought of as a class D amplifier driving a class AB amplifier and is therefore fairly complex.

How to Choose?
Regulated or unregulated? Class AB, D, or T?If you're really into a lot of bass, the class D or T may be for you as these amplifiers will produce the highest SPL with the smallest size. If you just want to wake the neighbors, blur your vision, or make a big splash in SPL contests, maybe you just need one of the inexpensive, powerful, & dirty class D designs. Want the cleanest high frequencies? Maybe a good class AB amp would be your selection. Whatever you choose, I hope this information helps you achieve the sound you're looking for!

see link for pics..

[D_bodyguard]

WOW ......sticky ....lol nice read though!!

[ruffneck_12]

I think Earthquake has Class J amps, 95% efficiency me thinkz

[ruffneck_12]

http://www.obadimports.com/gallery.html

^ class T amps

[noyztoyz]

i had a class T i think once from crystal mobilesound, rel top a d line ting, always wondered what class T was..

[viking1705]

nice post.this shud be stickied

[3stagevtec]

http://www.monstercable.com/mpc/stable/tech/A2412_Damping_Factor_Article.pdf

DAMPING FACTOR
By Richard Clark

At a recent AUTOSOUND 2000 manufacturer sponsored seminar, we were asked to comment on the
subject of amplifier damping factor. I was extremely surprised to find how much importance was attached
to this single specification. Since most folks are a little unclear as to the true meaning of damping factor,
we're presenting the following article.

First of all, let's discuss the items that enter into the damping factor calculation. At the heart of this
calculation is the output impedance of the amplifier. Most all-modern feedback type amps are of the
variety known as constant voltage. This means that they will deliver a constant voltage regardless of their
load - at least in theory. Sooner or later the limits of the amplifier's design will prohibit its constant voltage
characteristics.

It is this constant voltage output characteristic that permits modern car audio amplifiers to deliver more
power into a 2 Ohm load than into a 4 Ohm load. A perfect amplifier should be able to double its power
every time its output load is halved. Remember, Power = E x E divided by R. As an example, examine the
following chart:
8 Ohms = 25 Watts
4 Ohms = 50 Watts
2 Ohms = 100 Watts
1 Ohm = 200 Watts
.5 Ohm = 400 Watts
.25 Ohm = 800 Watts
.0125 Ohm = 1600 Watts

If an amplifier were theoretically perfect, then it would be capable of the type of performance described in
the chart. However, there are many factors that influence this capability. First there is the power supply
section of the amplifier. Even if an amplifier had an unlimited power supply with output transistors that
could handle the current, the design would still not be able to achieve the theoretically perfect output. The
reason being that we do not have access to theoretically perfect components.

Never lose sight of the fact that real components in real amplifiers are subject to real losses. These
losses are a result of junction losses; IR drops in connections and losses in resistances and reactance.
Losses in the output stages essentially form a voltage divider on the output of the amplifier. This drop is
always in series with the load and can be indicated as in Figure N.

In the design of an amplifier, the feedback network is usually wrapped around the section with the most
losses. These losses can be greatly minimized due to the fact that the feedback node is constantly being
corrected. This can be depicted as in Figure O.

Output Impedance Determines Damping Factor

If the output impedance of an amplifier is extremely low, the effect of loading on the output of the amplifier
will be minimal. This means that it will not experience a voltage loss across its own output impedance.
This output impedance does more than determine the effect of loading on the amp. It also determines its
damping factor.

Whenever a signal is fed into a loudspeaker the cone of the speaker will move. Since the cone has mass,
there will be mass in motion. Mass in motion means momentum. When the signal is removed from the
loudspeaker, the momentum of the cone causes the energy stored in the cone to be fed back into the
amplifier. If our perfect amplifier were connected to this speaker, the loudspeaker would be trying to
produce a voltage into 0 Ohms. Remember, a perfect amplifier has an output impedance of 0 Ohms
which is essentially a short circuit.

A voltage cannot be developed across 0 Ohms because it would require an infinite amount of current. It is
this same infinite amount of energy that would now be trying to prevent the speaker cone from moving. If
such were the case, we would certainly have a "tight" sounding speaker with absolutely no hangover.
The good news is that quality amplifiers have very low output impedances. We are very pleased to report
that there are many car audio amplifiers on the market with output impedances on the order of .01 Ohms
or less!

Calculating Damping Factor

Let's clarify a few points before starting our calculations. The frequency of the measurement and the
impedance of the load need to be specified. For example, the use of a 1 KHz signal and a load
impedance of 4 Ohms would be a typical specification.

DEFINITION = A good definition of damping factor would the ratio of the output impedance of the
amplifier to the impedance of the load specified at a given frequency.

An amplifier with an output impedance of 0.5 Ohm will have a damping factor of 8 when connected to a
theoretically perfect 4 Ohm loudspeaker (i.e. purely inductive voice coil.) since 4/.5 = 8.

The following chart assumes such a 4 Ohm speaker:
Output Impedance Damping Factor
4 Ohms 1
2 Ohms 2
1 Ohm 4
.5 Ohm 8
.25 Ohm 16
.125 Ohm 32
.062 Ohm 64
.031 Ohm 128
.0015 Ohm 256
.0007 Ohm 512
.0003 Ohm 1024
.00015 Ohm 2048
.00007 Ohm 4096
.00003 Ohm 8192

Now, for the bad news; it is easy to see how a race to produce such a high damping factor led to a
specification so often quoted by salespeople. The numbers on modern amplifiers (with lots of feedback)
can get very large and they are easy to compare. Sometimes we can get caught up in these big numbers
and we totally miss the point.

Effective Damping Factor (EDF)

In the case of damping factor, I believe that it could be compared to the old saying of not being able to
see the forest because of all the trees. The only thing that really matters is Effective Damping Factor
(EDF). Effective Damping Factor more accurately describes the interaction between a real amplifier and a
real speaker. Unfortunately real speakers have a real problem with EDF. This is due primarily to the DC
resistance of the voice coil. When we calculate the EDF of an amplifier and speaker, it is absolutely
necessary that we include this DC resistance into the formula. Figure P illustrates the inclusion of the
speaker's impedance into the EDF.

The actual impedance of the speaker may be 4 Ohms. If we measure the voice coil of this speaker, we
will probably find that it has a DC resistance of about 3 Ohms. When calculating the EDF effect on this
speaker, we must add the 3 Ohms of DC resistance as if it were a resistor between the output of the amp
and the voice coil of the speaker. Remember the resistive part of the speaker is the part where the signal
is turned into heat. No work is actually done in this resistance.

The inductive element of the voice coil is the only part that does work to create sound. This is one reason
speakers are so inefficient. Most of the voice coil is a resistive element that can do no work. Someday if
we develop room temperature superconductors and can afford to use them for voice coils, we are going
to see some really efficient speakers.

From the damping factor chart it is obvious that the most damping we can expect from our amp/speaker
combination is only about two. An amplifier with a damping factor exceeding 10 times this amount is no
longer going to play a significant role in this overall calculation. This would yield a practical limit on
amplifier damping requirements to about twenty.

There are times when the actual damping factor can exceed this number; one such case would be that of
a dynamic loudspeaker in resonance. As we have learned, at resonance a loudspeaker's impedance is at
a maximum level. At resonance, the DC element stays the same and only the reactance increases. This
means that the ratio gets larger and the DC element becomes a smaller percentage of the total.
For example, if the speaker impedance at resonance increased to 40 Ohms and the DC resistance was
still 3 Ohms and the amplifier were .1 Ohms, and then the actual damping could be 40/3.1, or 13. This is
certainly much better than 2, but quite a bit short of the 100, 200, or 500 claimed by salesmen who
unknowingly think this factor so important. Fortunately for most loudspeakers this extra damping happens
where they need it the most. This is because at resonance, speakers typically are very uncontrolled and
have the least mechanical damping. It is also this factor that enables us to be able to connect speakers in
series and not have to worry about losing damping. The actual impedance of the loudspeakers in series is
doubled, but the ratio to the amplifier must also be increased by a factor of 2 to 1. The result is no change
in performance.

It is quite possible that this information may be in stark contrast to current marketing trends. However this
does not change the fact that this information is accurate. The best way to achieve total control over
speaker movement is with a servo system. Only armed with a quality servo system can effective damping
characteristics be achieved. A servo essentially puts the loudspeaker in the corrective feedback loop of
the amplifier. This topic will be the subject of a future article.

[3stagevtec]

by Stephen Mantz

Damping Factor – This amplifier specification has been blown out of all proportion. What it means is the ability of the amplifier to resist a change in it’s output voltage. The formula is DF = Speaker Z/Amplifier output Z (where Z is impedance). So many manufacturers have claimed ridiculous, and often false damping factors. A damping factor of 1000 implies that the output impedance of the amplifier is .004ohm (4ohm load). The only way to attain this figure is to apply masses of negative feedback (or use positive feedback) and too much feedback makes amplifiers sound harsh and clinical. Also damping factor changes with frequency. The lower the frequency the higher the DF number. Typically the DF can be ten times larger at higher frequencies.

Let us take this amplifier whose output impedance is .004 ohms (Zout). The speaker circuit is a series circuit and the following impedances (resistances) are in series with this .004 ohms. Let us assume that this DF measurement was made at the amplifier’s speaker terminal. The first extra contact resistance is the speaker wire to the speaker terminal (WT ohms). Then there is that of the wire itself for two conductors (W). Next is the contact resistance of the wire to the speaker terminal (WS). Next there is the contact resistance of the wire from the speaker terminal to the voice coil (WV) and lastly there is the DC resistance of the voice coil itself (DCR). So what we have is a series circuit with the following resistances in series and adding up. WT+W+WS+WV+DCR+Zout. WT, W, WS, WV and Zout are very small indeed. Certainly less than .1 ohms. Whoa, look what has happened the EFFECTIVE DAMPING FACTOR has been reduced from 1000 to 40 by just taking into account those pesky unavoidable contact resistances. Now for the cruncher, remember that the DCR is also in series and is typically 3.2 ohms for a nominal 4ohm speaker. So we must add 0.1+3.2 = 3.3 ohms and now EFFECTIVE DAMPING FACTOR is now a magnificent 1.212! (4 divided by 3.3). This is the real world. We see that the DCR of the speaker swamps all other resistances in the speaker circuit and the .004 ohms amplifier output impedance is almost meaningless. It has been found that a DF of about 20 is quite sufficient to dampen the voltage spikes from the speaker. An eye opener this one is it not? Good tube amps sound marvelous – low damping factors!

_______________________________________________

here's another article from audioholics..

it's a long but excellent read..

http://www.audioholics.com/education/amplifier-technology/damping-factor-effects-on-system-response

[3stagevtec]

This one is for the Pro Audio Guys..

From
http://www.crownaudio.com/pdf/amps/damping_factor.pdf

UNDERSTANDING DAMPING FACTOR

Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing."

In other words, the speaker produces sound waves that are not part of the original signal.

Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope. When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb.

Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. Let's explain.

If the speaker impedance is 8 ohms, and the amplifier output impedance is 0.01 ohms, the damping factor is 800. That's a simplication. Since the speaker impedance and amplifier output impedance vary with frequency, so does the damping factor. Also, the impedance of the speaker cable affects damping. Thick
cables (with low AWG) allow more damping than thin cables with (high AWG).
The lower the amplifier's output impedance, the higher the damping factor, and the tighter the sound is. A damping factor of 1000 or greater is considered high. High damping factor equals tight bass.

How It Works
How does an amplifier control speaker motion? When the loudspeaker cone vibrates, it acts like a micro-phone, generating a signal from its voice coil. This signal generated by the speaker is called back EMF (back Electro Motive Force). It travels through the speaker cable back into the amplifier output, then returns to the speaker. Since back EMF is in opposite polarity with the speaker's motion, back EMF
impedes or damps the speaker's ringing.

The smaller the amp's output impedance, the greater is the effect of back EMF on the speaker's motion. An amplifier with low output impedance does not impede the back EMF, so the back EMF drives the loud-speaker with a relatively strong signal that works against the speaker's motion. When the speaker cone moves out, the back EMF pulls the speaker in, and vice versa.

In short, the loudspeaker damps itself through the amplifier output circuitry. The lower the impedance of that output circuitry, the more the back EMF can control the speaker's ringing.

To prove it to yourself, take a woofer that is not connected to anything. Put your ear next to the cone and tap on it. You might hear a low-pitched "bongggg" if the speaker itself is poorly damped. Now short the speaker terminals and tap again. You should hear a tighter thump.

Damping factor varies with frequency. As you might suspect, damping factor is most important at low fre-quencies, say 10 Hz to 400 Hz. The chart on the next page shows typical damping factor vs. frequency of a Crown CTs 600/1200 power amplifier. It's well over 3000 from 10 Hz to 1 kHz.

All Crown amplifiers are designed to have high damping factor. That's why you can count on Crown amps to deliver clean, tight kick drum and bass.

[- Rovin's car audio -]

^very nice


for those who new into car audio : http://www.glasswolf.net/papers/index.html ...

[carfreak1024]

wayz that last part 3 stage posted really clearing things up for me.

[Kasey]

so ah sealed box will add to damping? So it is better than ported for accuracy?

[1MADE]

Good Read

[3stagevtec]

--deleted--

[3stagevtec]

http://www.peavey.com/support/technotes/

Dig through the articles, some good stuff..

[ruffneck_12]

http://www.rane.com/pro-style.html

http://www.peavey.com/support/technotes ... _terms.cfm

definitions on words regarding audio/video and other electronics

[ruffneck_12]

http://www.peavey.com/support/technotes/

Dig through the articles, some good stuff..

more pro audio stuff
http://www.rane.com/library.html