What is your favorite material for loudspeakers?

Higher end Sonus speakers are more/less all curves. .. hence the heavy use of custom plies. According to Sumiko, by using these custom plies Sonus achieves higher rigidity/damping with low mass. G.

Sonus is an interesting case. . . rather than constructing speakers with plywood, they layer selected veneers in place with crossing grains into a custom ply pre-molded to the shape of the speaker. I understand that the top models use over 20 layers of veneer.

Interesting. . . in most cases, Baltic Birch is not from the Baltic region. . . it usually denotes a somewhat hiher grade birch ply from Russia, Bielorus, or China. Finnish birch instead. . . is a different kettle of fish. One of the highest grade materials I have found is from Finnish fabricator UPM, which can be sourced in thicknesses up to 50MM:
http://w3.upm-kymmene.com/upm/internet/cms/upmcms.nsf/$all/af4c54532110776dc22570ba00304034?OpenDocument&qm=menu,4,5,1&smtitle=Plywood
Material uses outdoors bonding agents and has 21 plies on the 1 inch thick product. This appears to be higher grade material than what is usually called 'baltic' or 'marine' plywood. G.

Johnk, the goals of cabinet construction for a string instrument and for a speaker are subtly different. . . a luthier uses the entire case of the instrument as a mechanically active amplifier. . . As such laminates like timber plies make for inferior student instruments because they lack the ability to propagate/amplify mechanical vibrations, not to talk about particle board which simply is anathema in cello/violin construction. The top of a cello is usually made from carved and finely graduated thin spruce. . . the bottom plate from almost equally thin maple or poplar. . . the two are mechanically coupled by an oaken post. . . . then of course there is the coupling to the strings through tailpiece, neck, and elastic maple bridge. The instrument is incredibly light and thin-walled, and vibrates and rings like it's going out of style. I haven't seen too many speakers that attempt to do the same. Hence, invoking the Cremonese masters is effective markcom, but. . . G.

Johnk, Sonus claims their cabinets are built like Cremonese string instruments of old. . . fabulously effective markcom. . . reality is different though. . custom ply cabinets of Sonus do not vibrate. . . they are desirably dead as doornails. But yes, it would be interesting to develop a speaker that truly vibrates like a fiddle. . . would probably be incredibly efficient. G.

Soundsrealaudio, this is very encouraging. . . if you consider that it took about 500 years for fiddles to progress from early Moorish example to reach the greatness of the Cremonese masters. . . while contemporary luthiers have already achieved respectable results having experimented just for a few years with carbon fiber composits. G.

I checked my old notes on birch plywood. One of the highest grades I have found is from a Finnish company called UPM. The standard UPM birch products come in 5x5 feet and 4x8 for product bonded with exterior grade glues. Price seems to be about $130 per sheet, but the importer (Plywood & Door) has a minimum of several sheets per order.
Max thickness for standard product is 1 and 1/8 inch with 22 plies per sheet.
I spoke to Rod at Plywood and Door
866. 738. 7265

The prices I mentioned are unit prices. . . I believe prices may go significantly down for quantity orders.

Fascinating article. Complete text at:
http://pubs.acs.org/doi/full/10.1021/nl802750z
Not material for speaker enclosure. . . actually looks like completely new technology for speaker design/construction. . . possibly eventual future alternative to current electrostatic bipolar designs. Technical details are beyond me. The article may deserve its own thread. G.