On another forum, there have been casual references to reducing edge effects on an OB.
Post 858
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100392&perpage=10&pagenumber=86JohnK recently posted 3 scenarios regarding OB response. 1 Flat, circular baffle, 2 Circular baffle with large round-over, 3 Flat, rectangular baffle with offset driver.
My thoughts were the rectangular baffle was very effective in spreading out the inverse peak, both in frequency and time. Would edge treatments such as holes in the baffle or felt edges be of further benefit?
Thanks for your time.
Doug
I suggested a few posts back (OK, maybe several hundred) that if you access to a NC drilling machine, drilling a series of random-sized holes close to the edge, with the hole size varying from 12 to 1mm, and the largest holes close to the baffle edge. I think I gave it a corny name like Progressive Loss Mesh, but the concept is simple: a random structure with progressively increasing loss, and all of the holes less than the minimum wavelength of audio frequencies.
The same principle is used for vented speakers with intentionally lossy vents - instead of a conventional duct, the vent is filled with closely-packed drinking straws, all of which have diameters much smaller than audio wavelengths, and act as acoustic resistors, not a duct.
Yes, if you were crazy enough, you could trim a zillion drinking straws to the depth of the Baltic Birch ply of the baffle, and pack them into a vertical slot, so they'd form an acoustic resistor between front and back. That would look truly strange, and I suspect would not work as well as the random array of holes.
In terms of the visibility of the holes, there have been some very attractive OB's using veneered wood only for the driver mounting area, and perspex/acrylic for the outer wings. (Some people have even used glass for the outer wings, although that is very heavy. I imagine the commercial versions of OB's use tempered glass to address safety concerns.)
I'd vote for perspex outer wings, with the computer-drilled hole pattern on the outer edge. It would have considerable visual interest, and would sound good as well. If you want a Museum of Modern Art look, you can trans-illuminate the perspex with an array of white and/or multicolor LEDs at the base, which would light up the outer edges, and make the perspex seem to glow from within. Now that would make a visual statement about OB speakers!
