Ed RazorLite

A port in a sub box is tuned to a specific range a frequencies, usually to match the frequency response of the sub. inside the box there is positive and negetive pressure due to sub movement, this creates air molecules to vibrate and move really fast. when this air moves across the opening of the port it causes the air inside the port to move in such a way that the port creates positive and negetive pressure also. essentially its like blowing air across an opening of a bottle. the diameter and length of the port will determine the tuning and when done properly the port acts as another driver because it effectively uses the back wave of the sub to match the front wave in the listening environment.

And fiberglass is not bad at all. I build boxes everday. I used MDF to build the frame, plywood is not good because it flexes too much. Birch is good too but expensive. I rarely ever get fiberglass on my hands or anything. I just use a pair of rubber gloves and go to work. If you are fiberglassing an area of the car, cover that whole area with masking tape, spray glue tin foil to the tape, then cover the foil in release wax or PAM and start laying fiberglass.Its fun

tahenke

It is a lot of fun because of what you wind up with in the end, a kick but form fitting purpose built enclosure! Another tip is don't be stingy with the tape or the tin foil. Mask off an area considerably larger than what you need and put down some plastic over everything you think you might accidentially drip some resin on (this will save on frustration later). The worst part is the sanding but since the enclosure will be behind the panel there will be very little (if any) sanding required Once you get good with fiberglass you can actually knock out a box quicker than you can with wood and way nicer. As for how thick to make it, a general rule is 1/4" thick. When youre done just spray paint it black (flat works best) to help hide it and you are on your way!

Ed RazorLite

Elmers resin and evercoat body filler sand nicely. Still a pain though

Lee3333

Well, I have officially given up trying to get good sound from a free air sub without an enclosure. I will now make my expensive compartment (lined with Dynamat) into a storage bin. Here is the adapter ring I made to ensure a tight seal of the speaker.



For my ultimate solution to getting great bass and still retaining use of all three storage compartments without giving up too much cargo space, see the following link.

By the way, I built a total of three (3) sub boxes (one ported and 2 sealed) as well as comparing them all to a pre-built ported Q-Logic box, and found my final enclosure to be the best both in terms of sound and compact size. It is exactly .754 cubic feet, just what the specs for the Kappa call for.

https://www.chevyhhr.net/forums/show...t=3464&page=13