The physics of multiple speakers.

[bishopdante]

This may be a silly question, but why is it that most speakers use a system of one driver per frequency band? Surely you could use many speakers positioned as close as possible to each other to produce a good wavefront. I would be fascinated to know why this approach has not been taken to PA speakers where stereo imaging is not as important. Most huge PAs are made up of massive arrays of individual boxes so this is in many ways the approach that they take, but I was thinking of smaller club systems. My thought was a driver size of around 4 to 6 inches, and a separate sub bass enclosure. Is this mad? it's certainly not conventional. I was also thinking individual amps for every 4 speakers. Would it help to have flat 'cones'? Would it help to have the baffle coated in a porous material? Could you design a horn/waveguide that would eliminate the areas between the speakers?

My thoughts on the advantages are these: Narrow dispersion (hence less volume decrease over distance), no mid frequency crossovers, Warm sound, very quick transient response, decreased point source sound.

You see, with PA, the idea is not transparency, but fullness and warmth. A clean system with linear frequency response will sound harsh at high volume. You would need a few tweeters though, I guess.

One thought I had is that loads of little drivers cost a lot more than one big one, and economics rule our world.

[johninCR]

Narrow dispersion is exactly the problem. You will end up with no horizontal dispersion due to the line array effect in all for directions. In the old days they stacked walls of speakers in that fashion. Later it was found that you get much better horizontal dispersion with vertical line arrays, plus it's less equipment to haul around. Vertical arrays of small drivers works well, but for drivers with significant power handling for a large venue arrays of small drivers would be less cost effective as you pointed out.

Small cheap drivers like those used for TV's can be very effective. I'm currently working on my 5th OB line array project using my favorite $1.50 driver 4" driver.

[Paradise_Ice]

How many amplifiers would you need to drive all of them? i only have 6, i find less is more and more is less, but then again, i never did make a wall of speakers, i think it would be over powering! but interesting!

[johninCR]

The more drivers you have, the less power you need. One of my arrays has over 106db of sensitivity, so it can be driven well even by a flea powered tube amp.