What can the front baffle for spkrs be made from?

Paul Hales used concrete for the front baffles for his earlier speakers. He later switched to 4" MDF (at least for the revelations, not sure about transcendence), which, and i think i remeber this accurately, was reported to have the same or similar effect as the concrete. Good luck with your speaker building.

AudioXpress ( www.audioxpress.com )just had a very detailed article that tested over a dozen different combinations for baffle materials. While the best choice would be something that was infinitely light and rigid ( which doesn't really exist or at least isn't commercially viable for speaker production ), the next best thing was MASSIVELY thick MDF.

According to the graphs presented, 2.25" thick gave the best results out of the materials tested. One can probably find better results going thicker, but that was as thick as they went. Keep in mind that these test results are VERY subjective due to how they were conducted, but the results do tend to agree with those that think a "dead" cabinet works best.

While I do think that Michael Green's idea of "variable tuning" of the cabinet itself might have "some" validity in specific situations, i would venture to say that it could introduce one more variable that the end user might not know how to properly use or dial in. As such, most designers typically try to minimize variables and go for the surest ( and most rigid ) cabinets that they can when it comes to speakers. Sean
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Read Martin Collom's "high performance loudspeakers", Vance Dickason's Cookbook of Loudspeaker design, and the two books by David B. Weems, those will all help. You can build it out of concrete, MDF, soapstone, marble, corian, special honeycomb structured aluminum composites, special plastics, etc. The deader stiffer stronger the material the better. They are all good, but beyond MDF they can be expensive and difficult to work with, albeit better.