I have the RF premium system with 8 spkrs. including the sub under the driver seat. I am pretty happy w/ sound and bass is not bad (someone had an idea on this site of opening up the enclosure and poly filling it partially. I think i'm gonna try that to tighten it up a little. At higher volumes it vibrates a little). Anyway, I want to add another sub under passenger seat, and was thinking of going with RF Punch series amp & sub. The area is only about 12" x 12" with 5" + change of mountable height. The models that look good for this size would be P2502 amp (250w x 1 bridged @ 4 ohms) and P38D2 8" sub (max mounting depth of 5"). I am told I can pickup the imput signals at the wires leading into the factory sub, and the remote turn-on from orange wire going from sub to factory amp. But I'm not sure if I should go with a ported enclosure or closed box, and whether to fire the sub downward or up. I don't want to blow the passenger's "you know what" out. Anybody have any experience with this?

it will give them a little massage. You will not get much bump out of it. I actually built boxes for the sub under the front seats, and they are a nice little sound finishing bass. I have a thread of the ones I built in the interior section.

here is the link

http://www.clubtitan.org/postt3396.html

Thanks Jay. I have seen your install before. You said I wouldn't get much bump? out of it. Is it because the enclosure would be too small? I would not be using free-airs such as you have. I e-mailed RF to see what enclosure size would be good for the models I mentioned, and the pdf file said the cubic feet based on using 3/4" wood should be at least .251
I was wondering how you mounted your amp to the back wall. Does it screw right to the sheet metal and if so, how do you keep the screws from poking out of the cab?

the enclosure is very small. Mine is barely bigger than the speakers. I forgot to measure them, before I put them under there. But it was trial by fire. I measured the space and found it did not fit, so had to get the peices under there and figure out were I needed more room. The depth on mine are 1/4 inch taller than the speakers and that was all i could get , so the speakers are almost tocuhing the floor. When trying this do not forget about the mounting on top. My speakers took up about a 1/4 inch on top, and had to readjust for that, since it would drag under the seat. I have not been much into the bump, but I have heard bigger is better for enclosure size.

The amp fit right in a indent in the back wall, and it fits so perfect no screws were neccessary, so I did not have to worry about the sheetmetal. Most people say there amp will not fit back there, but Ithink I have the perfect shape one to fit there. the seat holds the top still from rattling, and since the seat is sloped a little it still gets air.

What holds it from falling down when you fold the seat back down???

it sits on the floor, that spot on the wall is at the bottom