Even the worst internal shapes (i.e. round) can work just fine with a little foam. It doesn't take much foam to adequately kill the intenal cabinet modes.
I agree the curved shapes in cabinets look very nice. Usher, B&W, Sonus Faber all make a very nice looking round back cabinet. This looks high tech. It is very appealing to the eye! I like this look a bunch, and have considered many ways to build such cabinets. Such consideration is only present because of appearance. IMO, the only reason to build a nice round cabinet is because they look better. There are excellent acoustic examples of rectangular cabinets in VERY high end speakers.
F. Alton Everest in the Master Handbook of Acoustics addresses the issue of odd acoustic shapes. The essential summary is that ALL shapes will have acoustic modes. The placement of these modes can be altered by the acoustic shape, but the modes WILL be present. The only real method of dissipating these modes (without absorption) is via diffraction:
http://www.audioholics.com/techtips/setup/acoustics/RPG-Roomacoustics.htmlThe QRD works.
Now... to your questions:
This would however significantly widen the baffle which is probably not a good thing?
Er, you should keep the baffle approxomately the same width. Making the baffle wider will lower the onset of baffle loading in the midrange. I have not experimented with this, but know that wider is worse. This is simply because the crossover is designed to chop an appropriate amount of baffle loading for the current design. Increasing the baffle width significantly will necessitate a crossover change. The easy fix is to use a significant edge roundover and arrive at about the same baffle width. The flat portion of the current 1801 baffle is about 7 1/2". You should aim for this too.
If I keep the volume of the enclosure and the width of the baffle the same as your design can some shape changes be made without affecting speaker performance?
Yep, sure, you betcha'. As mentioned above, a little foam will cure even the worst cabinet shape.
I see that you have made changes in the way you put holes in your internal reinforcing braces. Has this affected sound colorations?
Nope.
Years ago I was very concerned about breathing room behind the woofer. I am not significantly concerned about this anymore. After some experimentation I have learned that a big open area directly behind the woofer isn't very critical. Some cross braces in this region are just fine. Futher, when looking at a woofer there is already a big obstruction directly behind the cone. It's the magnet/motor. I felt kinda dumb after 1-2 years of thinking about bracing configuration to arrive at this conclusion. A few cross braces are very minor when compared to that big whopping magnet behind the cone.
Egg carton type foam should disperse sound pretty randomly regardless of shape, correct?
Er, egg carton foam shape is simply convenient to cut and use. It absorbs sound, but has extremely small diffraction effect. I believe it's safe to eliminate the diffraction effect from the environment. While there is some diffraction effect, it's extremely small. Flat foam will work equally well to absorb the sound waves. This is all you will need to produce the desired effect.
Hopefully my response is adequate.
