This article is courtesy of Andy Wehmeyer
Ceo of audiofrog ans former top iasca competiter
If you're a car audio tech and you've been doing this for awhile, you've probably built this system hundreds of times. Install a new head unit, a DSP, a couple of amps, front components and a sub.
If you've built this a bunch of times, you've probably tuned this a bunch of times.
To make this sound good in one seat, there are a few basic audio processing tools you use to make this sound great--to make this win a competition, maybe.
Those tools are:
1. Crossovers. We have to limit the low frequency content that we send to small speakers to keep them from bowing up. It's a good idea to limit the high frequency content that's sent to larger speakers. This helps us create a center image and helps us blend the sound of the speakers so we hear the location of the sound in the front and near the location of the tweeters.
2. Delays, polarity and phase. We use delays to make sure that the sound from each of the speakers arrives at the same time, which puts the speakers in phase, so long as we have the polarity correct. That also helps to create the center image. When left and right speakers are in phase, we hear a sound that's recorded the same in the left channel and in the right channel in between the two front speakers. That's our center image.
Basic crossover design is predicated on simultaneous arrival time from the speakers to which the crossover has been applied. Delay is also important to make our crossovers work. When we get those two things right, we hear the image at or near the location of the high frequency driver. We hear the bass in the front and we hear the midrange and the midbass near the location of the tweeter. So, tweeters in the top of the doors, the dash or the a-pillar will define the height of the image--if we get this right. Some crossovers--second order, primarily, require us to swap the phase of every other band. That's because second order crossovers shift the phase and the high pass and low pass are 180 degrees out of phase. Other common crossover alignments don't require this because the phase change isn't 180 degrees.
If we don't get this right and the midrange and the tweeter aren't in phase at the crossover (where both speakers contribute to the sound), then instead of hearing ONE location (just like the center image when left and right speakers are in phase), we hear the locations of the two speakers.
This why we sometimes hear the bass in the back or the midbass low in the door.
3. Equalization. In order for the image to appear in the center and to remain there no matter which note the singer sings or the instruments play, the level and the frequency response has to match pretty closely when we measure it at the listening position.
All high performance speakers for home audio or pro audio or even car audio are designed to make this configuration work. All the other components in the system are also designed to make this work. A stereo recording is designed so that when it's played back over a system designed this way, we hear an image of performers and instruments in some arrangement from left to right.
These are the basics of what EVERYONE does when they design high performance audio (HiFi) systems.
