Using 16 inch and 12 inch shelving stock with simple butt joints and holding the 16 inch outside dimension, the clear dimensions inside would be 14.5 inches by 12 inches. R-13 batts are nominally 3.5 inches thick. Install them on the front and one side would reduce each of the clear inside dimensions by that same amount. The resultant internal "open air" dimensions would then be 11 inches by 8.5 inches. Given a 1 inch nominal thickness of material to "frame" the "window" opening would yield an opening size of 10 inches by 7.5 inches.

And as long as there's no crossover and we already have a port, couldn't I just wire the drivers directly to the posts on the amp and run the wires through the rear port? (Remember I like simple.)

BTW, using 16 inch and 12 inch stock (with the same cabinet height) the internal cabinet volume is only off by 0.16%, so I doubt if it'll make any sonic difference. (That amounts to less than the width of a saw blade when cutting on the wrong side of the line when cutting stock to proper length - which I'm more than capable of doing.)

Any amp suggestions for 2,000 - 3,000 cu. ft. room, listening to classical/jazz at 85 dB peaks?

thanks