Craig Leerman wrote on Wed, 13 October 2004 18:13 
Thanks Mark!
I always thought manifold subs had the drivers directly facing each other like a EV MTL cab and not splayed at an angle like this type of design. I guess I'll call this one an "Angled Driver Manifold Design cab!
Craig

If there is one seriously important factor to impress upon a class regarding bass reproduction, that would be the concept of wavelength and significant acoustic dimensions. We get past many matters of confusion if this is understood.
Go with an average of 1130 ft./sec. and you are close enough for the purpose. Now point out that in general, any distance less than 1/4 wavelength is insignificant to that frequency. At 100Hz, this would be 1130'/100Hz = 11.3' (11'3.6") for one wavelength. Divide by 4 for 1/4 wavelength and you find that a total distance of anything less than 2.825' or ~2'10" is mostly insignificant at 100Hz. Since the wavelength continues to get longer with lower frequencies, this distance is insignificant to all frequencies below 100Hz.
Now cover the matter of scaling, where 2x that distance, or about 5'8" won't have much effect below 50Hz. On the flip side of that, you find that at 1/2 wavelength, or ~5'8" at 100Hz is where you see a cancellation in this dimension. Think about it... If two drivers are 1/2 wavelength apart, and you are standing just outside one speaker, looking at the other, the other will arrive 1/2 cycle late, which is equal to 180 degrees, and so they cancel to a large degree(one is late, so they don't cancel perfectly).