ha.....i have built MUCH larger ones than that.....i'll have to dig up the pics, of doing that on a MUCH larger scale to "miss nude canada" with our old armored car at a show in toronto, which had a total of 60 15" woofers in it.......it would do 169db at 32hz.
this is from db drag finals in 1998 in nashville......
at 1:08 you'll see it......also there is a short shot towards the very end.......yes those are an extra 10 alternators being driven by the pto off the front......i'll see if i can find some more video......