Open Baffle Speakers: Question About Materials

When @ricevs (Ric Schultz) was making open baffle/dipole speakers and subs (employing the Rythmik Audio/GR Research Sub DIY kit) he made his baffles by gluing together three layers of 3/4" MDF, using Green Glue iirc.

One great method for creating very non-resonant baffles is to put a layer of ASC Wall Damp material between two layers of MDF or Baltic Birch Plywood. 

Yes, it is just as important for open baffle speakers as box speakers to have a stiff baffle. Spatial uses a thick wood material (I think it is a composite of some kind). PAP uses metal bracing to reinforce their baffle panels.

My open baffle speakers (based on GR-Research designs) use a separate enclosure for the woofers to handle the bottom three octaves, built with 1.5" high quality MDF. The second enclosure handles everything else and is built using a composite material.

If you have FB there are a few DIY Open Baffle groups