Lets say I were to make a speaker plate between the passenger cabin and the trunk and seal all leaks off between the two compartments.

Is it viable to use the volume of the trunk as a speaker box or are there just too many leaks to try and seal them all?

I'm trying to design a new setup away from the midget crushing 80lb 3/4" mdf board leviathan. So far I've got a snug fitting plate between the trunk and the rear seat, snug to the point of getting stuck after I add carpet to it. I'm working on the mounting brackets at the top which will bolt up to the triangular braces just behind the seats. Where I get stuck is if I should design a box that lets me get to the spare easier or use said idea above and go wild with sealant.

Any ideas? not looking for bass boomer, just clear bass and easy access to the spare.

(will post pictures later after work)

I would say that between the many small holes and the trunk lid seal it won't work. Every time the bass hits the trunk lid moves and you would not have a functioning box. The only way that would work if you had a free air sub.

Build a box and then seal it off

You'd have to seal your trunk 100%

This was a very common thing to do 15 years ago...mounting subs free air. It does work, however the sound you'll achieve won't be as nice as with a properly designed & built enclosure. The reason we did this back then was that we didn't have the selection of subs that we do today that are optimized for small enclosures. With the box sizes required for todays subs being so small, this method of installing subwoofers lost it's attraction.

However, if you elect to go this route, select a driver that has a Qts in the .6 to .8 range for ideal results, preferably with a Qms >10.

I figured that much, the advice came from somebody who had speakers mounted like this in his trunk a decade ago..

I don't have the space for a larger ported box which would be optimal so it's going to have to be sealed.

sub info:
Qts= .42
Qms= 12.11
Vas= 63.93L
fs= 32Hz

Pretty much for space requirements ~1ft^3 per woofer will be within the range I'm looking for. Sealed rectangular mdf box mounted to a high ply face plate. The box should have a resonant frequency around 76Hz. So it will be roughly 17"x32"x8" in total size.

the face plate so far, have not taken the router to the edges for angles or anything cosmetic:


just for reference, the old 4.3ft^3 midget crusher before you ask yes it was my first box and it barely fit into the trunk even through the opening from the interior with the seat removed:

yes, this is a viable option, but i would tweak the design slightly. I would suggest going with an aperiodic enclosure.

give this a read
http://www.elitecaraudio.com/article.php?sid=18

Not all drivers work well in these enclosures, or free air for that matter.


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My fault, I didn't have the correct specs on hand and looked up the wrong sub woofer. Had to redo all of the box calculations again..actual stats are:

Qts= .66 Qms= 12.11 Vas= 82.84L fs= 32Hz

still a very good read, but after seeing this:

"You will find that it is mainly the subs designed for ported enclosures that fit the bill, as subs designed for small sealed boxes (you know the ones...massive, heavy cones, stiff suspensions, heavy voice coils, etc) have a Qtc of .6 and higher. These subs tend to have a boominess that cannot be overcome with resistive damping and frankly, they sound like ass in an AP, so forget about em."

Had the Qts been .42 I would have seriously looked into this, but I'll stick with my sealed idea unless I'm upgrading the speakers themselves.

if you decide to go free-air make sure your subs are designed for it, and yes you can get them to sound as good if its done right. done right will require you have a really good trunk seal (maybe go buy a new one or find a good one from the junkyard if yours isnt tight) seal up all the holes in the rear deck, making some fiberglass bowl covers for where the trunk arms go thru the rear deck, pulling your side panels off and sealing up the holes behind them (the holes go straight back to the trunk) and making your cover go out to the metal of the body not just where the plastic cover pieces are. you have to seal it up well.


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