Ok, on the new box I built I have 1.395 cubic ft of airspace in the box. Right now I have one 12" Type R that has a displacement of .128 cubic ft. That leave 1.267 cubic ft. I am going to get another type R after I get the JBL 1200.1 amp and it will take away another .128 cubic ft. That leaves me with 1.139 cubic ft. The type R's are supposed to have .7~1.0 Cubic ft per sub, sooo, my box is a little small by at least .261 cubic ft. How much will this affect sound? would getting some of that polyfill stuff (ala pillow stuffing, I used it in my old box, seemed to help a bit) make up for the .261 cubic ft? And then if I put a divider between the subs that gives each sub .633 cubic ft. Should I use a divider or will it sound better without one? Do I need to rework my box or am I fine with what I have? Thanx for any help!

 

At best, poly fill can help fool the subs into thinking it's got an additional 10% of airspace.

Personally, I ALWAYS build my boxes bigger than what the speakers call for because I prefer a smoother response that you get from a larger system Q. If it were me, I'd build a new box for the 2nd sub so that they both get over a cubic foot each. Even at .7 cubic feet each, I think you'll find that they tend to be a bit boomy and drone within a narrow frequency band.

 

I would stick to the one 12" in a 1.267cu. ft. box. Each high powered 12" should get at least .8-.9cu. ft. (and that's a minimum for a "small" style box). You see, sub enclosures are like a sliding scale of performance: on the one end is the bigger box, these will make a more resonate rumble you will get, plus the subs will hit lower frequencies. On the smaller end, the subs will hit faster base rythoms and can be crossed over higher without causing distortion. This spectrum has a relivent range, with the small end at about .8cu. ft. per sub and the large end at about 2-3cu. ft per sub, but remember, the bigger the box, the more power you will need to make it sound the way you want. If you had enough power, you could make a box as big as space permits. Basically, when I'm designing a system for some one, the first thing I ask is, "what kind of music do you listen to?". If the answer is Rap and Hip Hop, the biggest box size would permit, or even a ported box would sound the best. If you're like me, you would answer Classic rock, Hard rock, Alternative, and in that case a small box is the way, but .633cu. ft. per sub might be a little small and produce short boomy base hits. For an FBody, you should be completely content with just the one 12" in the 1.267cu. ft. Personally, I have two Kicker Comp VR 10s in a sealed and fiberglassed dual chambered box with .8cu. ft. per sub in my 4Runner (it takes a lot more to make an SUV bump) with the amp crossed over at 100htz and I love it. I know some of you might think that's a high setting for the crossover, but I designed the system to hit higher base without distortion. That's why I went with a small box. If you set the crossover to 60htz (like most stereo shops to to hide high end distortion), music like ACDC doesn't even hit at all. I know that's a lot of information to digest, but I hope it helps.

 

yes the poly fill does help i couldnt believe the difference but i still dont know how it works

 

it slows down the resonant air in the box, "tricking" the subs into thinking theres more air in the box.