[71lemans71]

I have a 71 lemans and I'm wondering if any one on here has specs to buil a custom sub box

[sts]

The vendor I bought the system from calculated the cubic-feet, air-space for me. Actually, JBL calculated the dimensions because the vendor couldn’t do it; also, it took JBL a couple of days to get back with the measurements because they were a collective project from its engineering department, and they wanted to make sure it was right.

I supplied the maximum top and side, and the length into the car was determined by the top/side measurements. If I recall correctly it’s 5/8” particle board. I ended up with length in to the car calculated to 1/16” to make it a practical layout. As a result, I ended up with a 1 & 3/8” cube to attach inside the enclosure, adjusting the airspace to within .1” cubic inch of exact airspace, about as close to perfect as it gets. The delay in calculations was the cube; simply, without that cube, the length into the car would have been an ugly fractional numbers like 3/132”. All the speaker knows is how much volume it has to flex, not whether or not there is a small cube placed in the corner. By the way, it doesn’t thump. It EXPLODES!

The point is that for maximum performance, the cubic air-space needs to be matched to the speaker. The traditional way is an enclosure built to the speaker’s speck, and what-you-get is what-you-set into position. I suggest that you ask your retailer for technical assistance, and based on my past experience JBL was more than willing to calculate dimensions for custom enclosures.

[HJones1313]

STS is right, you need to contact the sub manufacturer with max dimensions. You'll find most all of them will have ideal volume specs on their website that you can massage to make fit your application, leave enough room for the spare etc. I strongly recommend that you use 3/4" MDF as a bare minimum for the box, heavily braced. You'll need to adjust the box volume to allow for the bracing too, which is just simple math, but tedious. Don't do what I did, and leave yourself with no trunk....