Bleach

So, do you want a sub box with a built-in rear strut tower brace or do you want a box so huge that it completely fills the rear hatch from the strut towers back?

1tuffz

my sub enclosure is sandwiched b/w the struts. we used marine 3/4" plywood [vs. mdf] for it rigidity and sound quality. i say we, but i had my friend who has built [his business] many pro competition cars in the past. anyway, i didn't want the weight behind the rear wheels as i do some autocrossing and a bit of track time [at watkins glen intl.]. by putting it between and fastening it to the strut towers it worked great for me. i still retain the use of my spare and the storage bins on my '73 240. he used a 10" jl audio sub-which fires backward into the hatch area [helping with the bottom end bass] with an alpine 100w amp driving it. the alpine indash am/am/cd powers the custom 5" kick panel/speakers. the system sounds great, doesn't rattle and is fairly light. while we had the interior apart we also covered all the plastic panels in a black tweed and used an upgraded fastener [sorry-a honda part to hold the plastic bumper caps on-no ricer comments please] vs. those lousy plastic rivets which always seem to get lost or damaged anyway. i've had quite a few people say they were very suprised that i only had 3 total speakers in the car-based on the sound quality.

David
1TuffZ
zccr.net

Bleach

Let me tell you right now, that even a 280ZX 2+2 could not fit a pair of 15 inch subs in a bandpass box in the rear area. I had a box for a pair of 12 inch in a bandpass and it barely fit with the back seats folded down in my 2+2. I couldn't even see out the rear view mirror! If you have a 2-seater forget about it.

You can fit the two 15s in there, but just go with a ported enclosure. if you have some good power to them, you don't need bandpass. Ported still brings out a lot more power than sealed but doesnt' take up nearly as much room as a bandpass. You will have to have them in the rear hatch area. Make the box full width and level on top. Maybe cover it with some black felt carpet or something so at night when people look in it appears to be empty in the back hatch. Also, get some dark window tint put on the back window.
If you are worried about weight savings for racing, then don't put in such a huge sound system. After all my sound systems, I have found that a single 12 sub has the best sound in the most compact size. You can buy a single 1000watt RF sub that will be more than enough for a Z. 10 inch doesn't go quite as deep, and a 15 is a little too big.