My knowledge of physics and science aren't worthy of any degree, but I've worked with the Gramma by Auralex long enough to say more than 'Dude it sounds gooder with it under my amp!'
I started to get more and more calls to play on demos and the Gramma seemed like it'd be a great home base to getting my amp setup and dialed in quickly.
If you search forums there are plenty of guys who think these are scams, truth is sure you can make your own, but Auralex made a quality product and for $50 I think it's worth every penny.
Today more and more bands are doing the DIY recording. Maybe you're going record in your friends basement or garage and chances are it is not acoustically treated. Sitting your amp on top of the Gramma will cancel out some of the room sound and give you more amp sound and less room.
There is a handle on the bottom that makes it easy to carry. I still keep the factory box to store it in just to keep it nice.
They make a few models and the Gramma is borderline too small for a 4x12 guitar cab. This is suited more for single speaker combos.
Heavy duty. It is supposed to be able to handle 300 pounds. At 180 pounds I stomped on it and it showed no signs of giving out.
Quit letting the room stand in front of your amp's tone, let your amp talk!
This review was originally published on http://www.musicgearreview.com