Just a thought. You could cut the area needed for two woofers in half if you built a clamshell isobaric box...

Isobaric boxes have a very small frequency range and will require you to know the resonate frequency of your cockpit in order to tune the box to sound decent.

Last year I was running these subs of this amp

http://www.crutchfield.com/S-RbetZxL...wer-T8002.html

While its a monster, and cranks out some serious power, its a real voltage sucker. At 2ohms, it puts out over 1000 watts RMS bridged(according to the brith sheet). Plus, its size is very large. I like to run the stereo while at the beach, and having that big fosgate and another old school amp for the mid's, just drains too much power.

I just purchased an Alpine PDX-5M, to run my 4 cockpit speakers, and 2 subs. I'm a bit worried now that this amp may not have enough power for the 2 subs. Rated at 300W RMS (actually closer to 400W according to the birth sheet) to the sub channel at 2 ohms. Considering going to the PDX-V9, which is also a 5ch, but has 500W RMS (around 600w according to the birth sheets I've seen) to the sub channel.

http://www.alpine-usa.com/product/view/pdx-5m/default

http://www.alpine-usa.com/product/view/pdx-v9

dont underestimate that amp .. you dont need 1000 watts to power hard hitting subs ... my first sub amp wAS A, M 1400 JL ,, 250 mono amp .. running two jl infinites .. now run a 1200 by 1 . jl hd amp .. with four 10s .. and i dont think its that much more thumping ... especially for all the extra i paid for them .. i run two kinetic hc 2400 batteries all day long . and roll over the motors just fine at end of day .. .. you need good batteries ... they pricey but people are blown away when my boat starts .. and so was i at first .. .. pdx line are awsom amps run them in my ski boat .. my new system has hd 600 , hd 750, hd 1200 ,, i love great sounding loud music .. good luck . glad you stayed on board love youre threads ..

Thanks Rob! I guess I can try the PDX-5M, and if i feel its underpowered, I can easily upgrade to the PDX-V9 later, since its basically same dimensions and hookups.

Joe, if you look in the manual there should be a table of Thiele-Small Parameters. You can enter this table manually into enclosure design software (I like WinISD) and it will generate a volume for you based on that data and some other stuff you put in, target frequency IIRC.

I have a PDX-V9, it's not installed yet, but it came highly recommended from a few members here, Griff being one of them. I'll have to get out it's birth sheet tonight and see what it says.

Here is a combination I run in one of the boat's a single 12 thin mount...it takes away all of the tuning issue's of a big box......... and use's by far less space........, a single 12 will be just as loud and have a more of a authority (hear Hit) than 10's........... Dual driver's in a boat are a bit like dual drives on a 20' boat....remember your 15' away at best....... proximity is what count's here......... two 10's doing 82 db will not have more sonic output than one 12 doing 84....... As to amp's they are just motor's no more no less....yes there is some integrity issue but the below amp is at the top or the heap in term's of sheer performance...there marketing suck's a bit but that's to you advantage. Don't let the refurb bother you they are under a 3 yr warranty...they pay the shipping and you get a new one back and yes they will run with the alpine line 7 day's a week 24/7 better service than brick&motor.

http://www.ebay.com/itm/Infinity-KAP...item2a312b5114

http://www.crutchfield.com/S-aDxs2Dv...-12TW3-D4.html

http://www.jlaudio.com/12tw3-d4-car-...-drivers-92185

If you build the proper box with that combination your only complaint will be with your boat and how badly it resonate's and you will have money left over for other essential's...

I think you have Isobaric confused with bandpass.

I would definitely go with the larger of the two Apline if you go that route. Both will be less power than you have now. I would suggest getting a bigger house battery for your system. I went from a series 27 that I would kill in a couple hours, to a series 29 that lasts almost all day. I run my system pretty hard at times and that 29 has no problem with it. I run 3 old school Autotek amps and they draw some heavy current.

I think you will be happy with the sound from the Alpine amp in you mid/hi's but not enough power to get the most out of the subs.

Something seems off to me,,, 4.9 cubic feet for a single sub???? How big is the sub?? in general in the car world I used to put 12's in a 1~1.5 cubic foot box and that worked nice. 4.9 is just not making sense to me.