Internal enclosure bracing

Material, box size, boxshape, and to a lesser extent box type.

With a subwoofer you want to push any potential resonances above the passband so that there is no energy available to excite them.

Easiest with plywood and properly implemented braces.

In a woofer, balooning can alos be an issue and each brace should tie 4 sides together.

And push-push (2 woofers a size smaller than a single) will dramatically reduce energy getting into the box — tightly coupled they have active reaction force cancelation.

Braces should be placed such that the subpanel formed by the brace has a higher ratio of length x width than th epanel they are bracing and they should be asymetrically placed.

dave