You are correct. Oh my gosh with two 15's that port cross section would have a very high port velocity, probably resulting in some whistling. And I rarely use round ports, they are less predictable and forgiving.

 

Well, if you look at the output response curve of a square or rectangle port, it is smooth. If you look at the same enclosure/driver combo with an equal cross sectional port area, only round, it will have a series of peaks that progressively get closer as the frequency increases. They both will work, but if you aren't careful, the first peak inside the usable bandwidth of a subwoofer setup can really mess with you. You could see as much as a 6-9db peak, and if you have a good ear, it might annoy the crap out of you.

 

Yeah, the hardest part of doing a job like that is having the vehicle here for fitting. I had the 4runner for a week just working on it nights and on a weekend.

I don't mind helping people out, but I would by no means consider myself a pro. I've probably done 20 or so fiberglass enclosures and countless other MDF boxes.

 

There can be an upside, alternating layers of fleece and matte can make the structure stronger. By having the fleece sandwiched by matte, you've effectively done the same thing. It can't be that much stronger, so I always put all the matte on the inside, with the occasional layer of fleece.

Just remember that the fleece is made of Polyester (Polyethylene terephthalate), and the resin is polyester resin, so you don't really have any structure in the resin if you only use fleece. The fleece layer is only to space the glass fiber apart, kinda like an I-beam's vertical stringer.

I've never used Spandex. It is made of a polyurethane-polyurea copolymer and will not bond with the resin as well as fleece. There are other fabrics made of polyester, but the fleece works well because it can soak up more resin resulting in a faster kick off and a stronger layer than thinner fabrics.