the SPL is also so what musical for a SPL based sub, im tuned below FS at 39Hz(it was saposta be 44 for a SPL box but i BBP6 ****ed that up) and it can sorta get low. it struggles with bluebarry yumyum and such, but for more rap and hip hop its fine. out put on the other hand is great. i did a 143.4 dB in my truck with 1 SPL 12 and a soundigital amp. one thing that we noticed was the impedance rise of the sub around tunning was 2.88ohms(coils wired in paralel) and my USamp MD3D just didnt have enough jam. so we had to call in the heavys to turn out a good numberactually i'd say tune to 40hz so it doesn't drop too low //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
I say go with the Mach5 audio SPL though, it's a monstrous sub and a damn good price. I've never had experience with one, but other Mach5 products i've used are pretty much solid.
NoWont 1 HDC3 15" and a 37hz box with 1.5k do UPPER 140's like 148
you need more than 1.5k for 2 subs if you want a lot of bass. Atleast 1k per sub.
I'd say 2 15's ported will be good but if it where me, id get 2 Fi Q's 12" and port them with 750w rms each, will sound nice and hit hard.
STFU2 13W7s.
No it wouldn'tit would be a great investment.