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I humbly solicit advice to avoid running myself in further circles:

Have an OS Punch 12" DVC HX2 in a 1.25cu ft sealed box that flat killed it in my old Nissan hatchback(rear-firing corner loaded using hatch to make folded horn) running off the rear half of an RF 4004 (BA 6.5Pros on the front, Alpine CDA-9855 HU, 1F cap). I built a nice 3/4" plywood spare tire shelf to hold it up and it sounds great - BUT... I get nowhere near the output my old hatchback had...

I use no rear fill, therefore the stock 6x9 holes are wide open.

I have tried to corner-load it (was great with rear seat out/down) and tried loading it into the rear seat. with mixed results thus far.

Am trying not to throw more power at it (have more amps), or start giving up my whole trunk to additional drivers. I have a solid 2nd-order bass reflex box that is right at 2.0cu ft and tuned to 30Hz originally built for this sub, and a fairly esoteric .75cu ft sealed bx that has run 2-12" DVC's (both OS RF and type-S alpines) in a push-pull that was very deep in the Nissan but the sealed 1.25was chosen for overall SQ, output, and space considerations.

I also am not a fan of bandpass, unless that is the only way to get what I want outta this thing. My other vehicle is quite loud, i just want all i can get out of my current setup if possible.

Ideas, anyone?

TIA!

 
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Hatchback vs. trunk is drastically different acoustically, that's the source (obviously) of this issue.

My first question is what frequency is the sealed box tuned to?

In general, sealed boxes in vehicles in the trunk work real nice when tuned to around 40-50Hz. (I realize this seems a high frequency but vehicle transfer function will completely change that curve.)

The .75 cu ft (I think you're saying Isobaric setup) probably will not get you any closer to what you want.

 
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Definitely food for thought - I haven't done a 'trunked' car since '88 or so...

IIRC 1.25cu ft box for the HX2 is about 35Hz. I think .75 is about 40Hz+ or so with that same speaker, so that may be an easy and small-footprint solution and I generally don't like vented enclosures for SQ reasons.

I have also tried to rear-fire the 1.25cu ft box from against rear seatbacks into open space and got more output but it sounded sorta 'tubby'.

Just out of curiosity: Earlier today I made a .75cu ft sealed box + adapter ring and mounted my old Alpine 12" type-S speakers in a 'face to face push-pull' configuration rear/up-firing (abt 35 degrees from vertical) with back of cab against rear seatbacks. It is heavy/ugly as hell and draws lotsa current thru the amp but goes very deep and gets pretty darned loud - makes me wonder what the lone HX2 would do in that same box since I had long ago forgotten the car-coupling end of the equation.

Thanks!

 
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I built a couple of boxes a year or so ago. they are made for 10's and are made to fit on either side of the trunk. each box is 1 cu foot and is sealed. they aren't super loud, but they sound amazing, as the boxes were designed with the sub in mind. I'm sure you know this, but if you look online at the specs of you sub, you can find the throw and other stuff, punch it in a calculator that you can also find online, and it spits out a cubic foot rating that is perfect for your sub. also I had a 1.5 farad cap, which didn't work. it pulled all the power from the battery, and the rest of the car would drop to 6 or 7 volts right after the sub hit. I'm not sure if it is just me with this problem, but you may run into it as well.

 
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click the link on sub boxes and we can talk if you want one

 
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My 04 got smashed 4 weeks ago and after the second trip to the body shop all appears to be correct again (I'm a picky bastard)...

But more importantly, and since I have/had plenty of 3/4" MDF - I made a gargantuan 2.4cu ft 2nd order box with a 4" aeroport tuned to to 33Hz containing a 4ohm dvc OS RF HX2 wired at 2ohms (using a subsonic filter to keep amp from going into protect mode from uber-low impedance in bridged mode). Mounted rear-firing with back of box against rear seats using trunk area as a folded horn to pressurize interior thru open rear-deck oem speaker holes.

and a bulk-pack of Dynamat Extreme...

It absolutely hammers! This is the first vehicle in which I've actually had to use the visor mount for my Valentine One because it won't stay on the windshield at low freqs Amp does not overheat, and fit my 'simple' design goal of 1-4(3)ch amp, 1 cap, 1-12" sub, 2-6.5" midbass, 2-1" tweeters.

I saw a lot of interesting ideas here in the forums, and will keep my 1.25cu ft sealed box/12" dvc combo in case I want the trunk space back later.

 
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give us some pics!

 
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Here ya go, I'll finish the trunk out when I get to feeling better (I'm still kinda beat up from the impact). Subfloor will be 3/4" birch plywood and trunk will use modified stock carpets on floor & sides with very close matching carpet on the box.