Advice with sq install

[- Rovin's car audio -]

u can make a small fiberglass sub enclosure to fit on d side in d trunk ....

[kavaninho]

There many places for a sub without sacrificing trunk room.
Reardash/Under seats/Passenger footwell.

keep us updated with some build pics.

[Brian Steele]

The crossover points on the deck for the low pass only goes up to 250 which is a total waste since the 8s can go up to 5500hz

LOL - likely only if it was facing you directly . An 8" driver will start "beaming" long before then. You can expect the off-axis response to start dropping a lot earlier than 5.5 kHz. For example, here's some measurements I took of the Eminence Beta 8A in my Blastorama project that show it's off-axis response. I was trying to determine the best x-over point. Around 2 kHz or below seems best, but I eventually ended up with 3kHz for a number of reasons, including I didn't want a fuckwit at the volume control blowing up my tweeters because they were crossed over too low.

Or I can go two way and have a simpler setup since the tweeter can play down to 2000hz

"Can" is not the same as "should" .

[infinite_RPM]

Yeah I know lol.. I not gonna cross at those redic freqs.. I was just saying lol

Just for fun resp graphs

This tweet is one of those planar tweets... I went a lil overboard at parts express and buy stuff

Tweet

Woof

[TK!]

Sq posts

[infinite_RPM]

do the components affect final impedance in the crossover? Or does it operate like a normal circuit in terms of impedance calculations?

[kavaninho]

Not exactly sure what are you asking, but the impedance you enter into these calculators (or calculating by hand) is not the nominal impedance on the datasheet. The impedance vs freq. graph must be used and read off at the required cross points. At least that's how I learned to do it and does make sense since the impedance you entered would not be the load presented at the given frequency. Remember the loudspeaker is a reactive load.

Not sure if it works the same way with subs because the box messes with the impedance curve a bit. I should do some more research on this.

[infinite_RPM]

I tried the calculator with an actual crossover and it seems to work with the nominal impedance

[ruffneck_12]

yea it will work

but your amplifier 'sees' a load whose impedance changes with frequency

And adding a crossover to this mix changes that impedance relationship as well. I'm doing some research on this right now, can anyone tell me how to accommodate for this when designing a crossover?

[infinite_RPM]

Yeah I should of been more clear that's what I wanted to know lol.. like if u have a speaker with an inductor and capacitor on it if it will affect the impedance.

Need to know to finalize crossover design so I choose a suitable amp

[kavaninho]

I think you're over thinking that impedance thing a bit. Normal parallel rules still hold. Two nominal 4ohm components would need a 2ohm stable amplifier although connected using other components that make up the xover. That is assuming no attenuation resistors are used.

[Brian Steele]

I think you're over thinking that impedance thing a bit. Normal parallel rules still hold. Two nominal 4ohm components would need a 2ohm stable amplifier although connected using other components that make up the xover. That is assuming no attenuation resistors are used.

Um, no.

The attached image shows the combined impedance of an Eminence Beta 8A driver with a 1" tweeter in a CD horn. The impedance curve is in grey, and an adjusted one using impedance compensation (for use with cheap class D amps) is in blue. The Beta8A has a "nominal" impedance of 8 ohms, but its actual impedance can do down as low as 5 ohms. The tweeter has a nominal impedance of 8 Ohms. The combined impedance of the x-over and drivers does not drop below 5 Ohms, the minimum impedance of the Beta 8A.

I'll give you an example of a badly-designed x-over shortly. And this in what used to be a commercially-available system too.

[Brian Steele]

...and here's an example of a bad x-over. This was a commercial three-way pro audio system. Note the impedance drops BELOW the minimum resistance of the bass driver (around 5 ohms) between 80 Hz and 400 Hz, and again just below 2kHz. This could have been avoided with proper x-over design.

[infinite_RPM]

https://www.sonicelectronix.com/item_12 ... -8BXP.html

What y'all think?

And thanks for the info Brian, I'm always up for learning but this seems like a super simple solution instead of designing a crossover, with this I'll have flexibility

[infinite_RPM]

And to continue the discussion.. how is a x over properly designed to avoid this

[kavaninho]

I think you're over thinking that impedance thing a bit. Normal parallel rules still hold. Two nominal 4ohm components would need a 2ohm stable amplifier although connected using other components that make up the xover. That is assuming no attenuation resistors are used.

Um, no.

The attached image shows the combined impedance of an Eminence Beta 8A driver with a 1" tweeter in a CD horn. The impedance curve is in grey, and an adjusted one using impedance compensation (for use with cheap class D amps) is in blue. The Beta8A has a "nominal" impedance of 8 ohms, but its actual impedance can do down as low as 5 ohms. The tweeter has a nominal impedance of 8 Ohms. The combined impedance of the x-over and drivers does not drop below 5 Ohms, the minimum impedance of the Beta 8A.

I'll give you an example of a badly-designed x-over shortly. And this in what used to be a commercially-available system too.
2016-10-12.png

thanks for enlightening.

[Brian Steele]

https://www.sonicelectronix.com/item_125483_Audiopipe-XV-8BXP.html

What y'all think?

And thanks for the info Brian, I'm always up for learning but this seems like a super simple solution instead of designing a crossover, with this I'll have flexibility

Yes, active x-overs do offer a lot more flexibility. DSP offers even more flexibility (x-over slopes, time alignment and EQ).

[Brian Steele]

And to continue the discussion.. how is a x over properly designed to avoid this

Simple - design with impedance response as well as frequency response and power-handling in mind . This in turn requires the use of a good x-over design tool like XSim that can easily model these things.

Here's what the impedance response of a redesigned x-over for this particular speaker looks like. There were still one or two issues with this particular speaker that needed to be addressed when I took this measurement, a few that can be quickly identified from the response curve. I decided that the dip at around 1.8 kHz was small and over a very short frequency range, so it did not warrant any work to address.