I am in the process of finishing up a similar project myself!
I wanted to get a 5" radius edge on my speakers to minimize diffraction effects. Indeed, it is highly effective.
I went through three methods before hitting on a successful one.
First was to use 10" PVC pipe, cut it in quarters and glue the quarter pices to the edge of a box that has been built with a "step" of sorts on the edges. Unfortunately, I found that once I cut the PVC, it curled in some to a smaller diameter, making the box I had built the wrong size.
Scratch that. Didn't seem like the best idea.
Next idea was to laminate six 4.5" wide pieces of mdf together for a billet 4.5" square. Then I drew the arc on the end of the stock and ran it through the table saw 5 degrees at a time. After that, sand with an orbital sander until it is smooth instead of faceted.
This worked pretty well, but the radius was not perfectly linear in spots, and it produces an INCREDIBLE amount of MDF dust, which is hell to work with.
Current method; and this is working quite well now... I made a box with a skeletal rib-work for the cuves on the edges. Every 5 inches or so there is a routed curved piece. (I added more ribs after the shown picture)
http://www.hoppehome.com/Rounded Cab.jpg
I then used double-stick tape to attach a plastic sheet to the ribwork (similar material to overhead transparencies) and fiberglassed it from the inside. Peel off the plastic when it dries and there you have a nice smooth form to veneer over! Also, it is very strong and will not resonate, due to it's curved shape.
I will need to do a little bondo and sanding to get it just right, but this method is workind well.
Another good possibility is to use the flexible bending plywood that can be found at good lumber stores.
Also, you could cut deep scores down the length of a piece of veneered MDF of some kind and bend that around a form as well.
Hard work, but I think it's going to be worth it...
[Edited by Phloodpants on 12-03-2001 at 06:27 PM]