David,
I put this same question to Cube Audio a while back and got this response:
"Hello Mark,
The simplest way is to make a platform with a slightly larger cabinet outline at a local carpenter, with acoustic polymers placed underneath. It may be a rubber element that dampens vibrations very well.
We have often seen such solutions in rooms with long pile carpets.
I hope that this solution will be helpful."
Best regards
Ewa
David Ten infers the efficacy of maintaining the "tilt" angle with the small rubber domes in the rear of the speakers and the spikes in the front to perhaps to give the bottom-firing bass response to be optimal. I personally dislike speakers with a tilt and at the moment have the speakers level with rubber/foam blocks from McCarr Masters under the corners resting on slightly oversized 1/2" MDF pieces of wood on my carpet. Not addressed in the response I got from Cube Audio is the issue of whether the opening on the bottom of the Cube speakers is optimized with the factory "tilt" similar to sizing a bass port on the back of speakers, which is not trivial a matter.
I started with the factory tilt on my thick wool carpet and it clearly muffled the LF response. Leveled up on the wood platforms with rubber/foam blocks on the corners yielded a massive improvement in the LF as might be expected.
Any thoughts, David?