In mid/late July (2002) I built some speakers with my friend Stephan (the other half of KromoZone). They were speakers originally designed by Dan Trueman's father (based on some research done by Perry Cook at Princeton) and built by Stephan under the mentorship of Curtis Bahn at RPI. They have powerpoint presentation about the first batch.
Here are some pictures of the second batch, which I was privledged to be a part of in construction. As you might notice from the pictures, they are built in "hemispheres" of six speakers each.
The speaker drivers are Polk DX-4 coaxial speakers (meant for car audio). The 4" speakers have a range of 65Hz-20KHz with a power rating of 80 Watts @ 4 Ohms. They are wired together as 2 sets of three (which is to say 3 in series, with the two sets in parallel), making the array 6 Ohms - close enough that no damage will come to the speakers.
The construction of the enclosure was done with MDF (Medium Density Fiberboard). 1/2" thick MDF was used for the 6 sides (5 trapezoids, 1 pentagon - all appropriately bevelled), and 3/8" MDF were used for the 18 1/2" disc that is the base. The circles were cut with a circle cutter on a drill press (with jigs to line it all up). The trapezoids each had a biscuit notch cut in them too, and then biscuits were inserted between the pieces to help keep them together on the glueing jigs (BTW, the key to the whole project are these fantastic jigs that they designed with the aid of a fabulous guy named Sid. The whole thing is glued together using wood glue.
Inside of the enclosure, every nook and cranny is sealed with Silicon Rubber. After sanding the outside, the enclosures are ready for painting. Stephan manged to find a really cool auto-body shop in Troy who were into painting them - so the paint job is truely superb (and yes, you can buff out scratches in the paint!).
When they are ready to go you can fit a "sphere" - that is two halves - prefectly into an SKB 16x14 tom (drum) case.
And they sound fantastic...