I've drawn up some preliminary plans for a larger cabinet with an internal volume of about 9 ft 6 in (before any internal bracing). Briefly, internal dimensions of W 26 in x H 43.5 in x D 14.75 in. This will result in a W 27.5 in x H 46 in x D 16.25 since I will use 3/4 in Baltic Birch plywood all around and will sit the speakers on 1 in spikes, or maybe a 1 in pedestal. The GPA datasheet for the 604-8H-III also recommends 2 round ports of 5.25 in diameter x 2.3 in long ducts, so will try that to begin with, too. Will place the ducts on the back panel approx 16 in above the internal floor, which results in the center of the port being approx 17.25 in below the center of the speaker.

Billfort had remarked in some of his posts that he wanted to keep the front baffle width 26 in, b/c with narrower baffles he felt like he lost some bass. Because my wife was more concerned about keeping the speakers from sticking out too much from the wall, I went with a slightly wider internal width, resulting in a front baffle width of 27.5 in instead of 26 in. I don't think the wider baffle will be a problem, but I'm not really sure, either.

These cabinet dimensions will result in the center of the speaker being 35 in above the floor, which may be a little low since my ears will be about 42 in above the floor. I figure I can always tilt the speaker back a bit if this seems to be a problem. This also leaves 3 in from the edge of the speaker to the top of the cabinet.

If anyone sees any "fatal flaws", or has any comments/suggestions, would be glad to hear about them!

Dave