picked up a JL 10w0-8 to throw in my truck. would have loved a lower ohm sub but the price was right.

local shop suggested an alpine MRP-M500 i need 200 rms at 8 ohm. sub is going to be going in a small sealed box. looking to get something to power them cheaply but it needs to be small as i have limited space available in the truck.

i was going to do a box to have the sub firing towards the rear of the back seat (almost up against it) but the local shop suggusted to have the sub fire towards the seat but partition it to fire downwards and between the seat back and the seat bottom (guy has worked on kicks before so he knew about the large gap in the seat)
so the bass wasnt wasted when the top was off.

so for the amp what am i looking for power ratings, (nothing is shown for 8 ohm, most ony show 4 ohm for specs)

At an 8ohm load your not going to get the power of out any amp that you should. You can get a lot more power and punch out of your sub with a 4ohm or below load on the amp... I would not waste my time with the additional design and build of a box that ports out through the 'crack' in the seat.. it's not necessary and will provide you with minimal (if any) improvement unless you have the proper airspace in front and behind the speaker... The design you are showing will essentially work like a ported box and will require much more room on the 'ported' side and will actually make your speaker work against it self unless properly designed.

You are looking in a decent power range, but I know nothing about the newer Alpine Amps (the use to be good for mid and high range speakers but not real good with the pull of Subs... Just do some on line research to make sure people are not having issues with them overheating and clipping out under the load of sub's.. also make sure it has a built in low pass crossover built in if your head unit does not have a sub out RCA.

Since you got the JL 10 8ohm for a good price, I would sit it in a sealed box and run it until you feel the need for more... then upgrade to a 4 ohm or a DVC sub in the future.

Zig

i gotta agree with Zukipilot.  it wont be worth your time to have it come thru the seat.  if your not dead set on a "seat fired" sub, i had down fire ones(basically turning the design down so the sub is on the floor boards) but if you do that you gotta have enought of a spacer so it doesnt shatter the rim of it.  Good luck, post it when your done!

is it going to be bad if the top of the sub box is against the seat? almost sealing off the box from venting sound up. im building the sub box into a full box for the trunk so i can have a locking rear compartment with my rear door.

im going to be building the box to have a lip to protect the sub (sitting the sub away from the seat)

should i leave an air gap (1") across the top to vent? (probably mesh it to keep it from getting things shoved down behind the seat.

depending on the size of the sub itll be more like a massage for whoever is sittin there.  if you want it to be loud it would be better to have it be firing down or backards towards a hard surface so it will resonate better.  i had 2 12s in my single cab truck facing the seats and it was loud but when i turned them around to the back of the cab it was a noticeable difference

what im worried about is its a soft top kick. so if i have them facing back its going to just hit the tailgate and go up and out.
also ive heard the rear tailgate likes to rattle like theres no tomorrow when a sub is pointed at it. so my thinking is the next best thing is to point it forward towards the seat. what if i still did the box style that had the port to push it down under the seat but also have it open at the top to vent there as well. but have a wood plate against the seat to minimalize the vibrations coming through the seat?

ok, ive made up my mind, im going to have it fire downwards and open to under the rear seat back (2"x15" opening)

ive checked out a couple places for amps and im being told to run the alpine mrp-m500 or the pioneer gm-d8400m both are rated for 300 rms x4 ohm which should give me 200 rms at 8 ohm, just what i need for that sub. just wondering whats going to do it better, both are pretty evenly matched. or is there another brand you can recommend.

i have never had any alpine stuff altho they are really good at what they do/make.  its not great but im a fan of Sony, quality on a budget