I have been interested in exciter based panel speakers since I started reading the thread, "NXT.....rubbish??...THINK AGAIN!" in the circle "Open Baffle Speakers" several years ago. I spent most of my spare time for about a year experimenting with corrugated cardboard panels treated with shellac, trying different sizes, shapes, thicknesses and layers of cardboard, different numbers and types and mounting positions of exciters, etc. The end result, so far, is a panel about 2' x 3' of single thickness corrugated cardboard with a second layer added around the perimeter, powered by 2 exciters placed in the first 2 Monacor positions, suspended by cotton string placed through a hole in each upper corner of the panel.
Danny was willing to give these a listen and do his usual thorough job of testing them, so I packed up 2 panels and sent them off to GR Research. One of the panels is just a single layer, the other has the double layer edge treatment. To my ears, the added layer somewhat improves FR by increasing the bass and reducing the treble.
I am really interested to find out what Danny measures, and what he thinks about how they sound; I hope some of you will be, too. These speakers are incredibly cheap (less than $20 in parts for the two panels I sent). As I told Danny, I think they have their good and bad qualities--I am amazed at how quick and detailed these funky cardboard panels are. They are very efficient and play quite loudly, with big character.
We'll see what Danny says.....