Again, I will say you do not need aluminum to make a great line source speaker with Neo 10s and 3s. Look at this thread again:http://www.audiocircle.com/index.php?topic=142235.0
He is using two 3/4 inch pieces of 13 ply birch plywood and a piece of 3/4 inch highly refined particle board with green glue in between all layers. This is very rigid....is it as rigid as much thinner aluminium? who knows. His speaker can be made to look much better with veneering and just a small layer of felt around the front drivers....it would look very good. You could also round and flare or sculpt the top or bases, etc, etc. It can look as good as your imagination allows. He did not care what they looked like (has his own basement) and therefore spent no time on looks. You can also flare out the backs of the baffle where the drivers are to give the drivers more air to breath and more dispersion....still, I would put felt in those flares to smooth the response and, of course, felt on the wing.
I have no doubt that these speakers sound better than the big ones Danny made with the aluminum baffles because the xover parts and wire and connectors (none) are way more transparent than what Danny uses. Maybe an aluminum baffle would give you 5 percent better sound? Certainly the better xover parts, wire and no connectors would give you 20% better sound.
My friend Miguel, who owns the aluminum speaker that Danny had built for him, is ordering better xover parts and wire now and I am sure he will be thrilled with the difference. The original idea for that line source speaker came from me. I sold Miguel on the idea and made him a super modded Behringer xover to tri-amp the speakers with. Miguel decided he wanted an aluminum baffle and tried to find someone to make it for him. Since he as buying the servo woofs and amps from Danny he called him and they talked and that is when Danny decided to help Miguel with his "dream speaker" and then Danny could then bring out a new model of Serenity speaker based on this proto. The next speaker up from the "super 7" that Danny had imagined was an over $100,000 monster made from carbon fiber and had a ton of drivers.....see this thread: http://www.audiocircle.com/index.php?topic=110891.0
Bottom line is you can make a seriously great (and great looking) line source using Neo drivers using 16 ply birch and highly refined particle board mit green glue. Even the one shown with 4 Neo 10s is 96 db efficient and kicks butt. About $3700 for the Neo 10s and 3s for a stereo pair (4 Neo 10s and 12 Neo 3s per side)....add woofs and amps (three servo 12s per side) and xover and wood and felt and veneer and xover parts and wire and you are looking at about $7000 total with everything. Not cheap but oh my....what sound you would have. My home made speakers use one Neo 10 and one Neo 3 per side and with great xover parts, felting, wire and no connectors (all on open baffle) it sounds really, really great. I have no speaker envy.