Originally Posted by mandos

You don't tune a sealed enclosure, a ported enclosure is tuned based on box size/port length/area. A sealed box, you can change the size to slightly move the place the box peaks but it definitely isn't tuned in the same sense of the word.

Plus, modifying box size to change the peak of the enclosure severely changes how the speaker reacts in said box. Granted, a ported box will change the behavior as well, but generally won't change the sound as severely as just...say...making a sealed box bigger to lower the tuning.

When building a sealed box, most people aim for a specific Qtc in their car of .707 which is the "ideal" box with the flattest response. Obviously putting this same box in different cars changes the response based on cabin gain though.

http://www.carstereo.com/help/articles.cfm?id=29

^^ that's a good explanation on Qtc

Looking good, we had a similar set up to that in our GTi once upon a time.

And 3 on the same power will definitely be louder, no way to really get cancellation as long as it's crossed over at 60ish Hz, at which point the waves are so long there wouldn't be any sort of cancellation in a tC.

The other advantage to more drivers in SQ competition is that they have more surface area, less distortion since to reach the same level(volume wise), each sub travels less.