Wayne Parham Messages: 18790 Registered: January 2001
Illuminati (33rd Degree)
Sorry, Jeff, those dimensions aren't close enough to the three π cabinet that I'd feel comfortable making an assumption that the standing waves will line up the same. Down low, certainly they will, but up higher they'll be much different. And it's the midrange we're concerned about. I'd definitely model and/or measure the speaker, watching what it does above 150Hz or so.
The three π loudspeaker has outside dimensions of 30" x 20" x 13-1/2". That may seem pretty close to what you propose - and it is - but the difference is significant both in terms of overall volume and in the distances to interior cabinet walls. This will make enough difference you can't really compare one with the other in terms of where standing waves line up inside, particularly at the higher multiples, above the fundamental standing wave nodes. That's usually what you have to watch out for. It is important that the woofer and port not be near standing wave nodes ideally at all harmonic multiples from the fundamental up through the woofer's passband, or at least up high enough that the insulation can effectively damp the sound.