Subwoofer and bare floor

I have discovered that I get better bass from my speakers (hybrid electrostats with integrated subwoofers) if I put a folded up towel under the down-firing base drivers. I have them on bare floors, normally.

Does anyone have an explanation for this? Is it common for subwoofers to work better on carpeting than bare floors?

In case anyone is wondering, I discovered this while moving the speakers around to try different placements: I put them on towels to slide them around. Usually I take the towels out before playing them, but this time I forgot. The difference in sound is really striking.
Depends on the woofer and the type of floor. I use Auralex Gramma (or SubDude) between my sub and the wood floor. It reduces the floor resonances.

Auralex Gramma? What is this and can u send us a link?
is it softing the bass and making it more defined? you still have the speakers spiked? Or is it coupling the speaker tot he floor where you are feeling more vibration.
Each speaker has two 10" bass drivers in the same enclosure, one driving down, the other driving forward. Each has it's own internal amp.

The two drivers clearly must interact with one another, and on the bare floor it seems the forward-driver doesn't produce much sound. With towels underneath the bottom-firing units, there is a lot more sound coming from the forward-firing units. I wouldn't say the bass is softer, or more defined, it is not as subtle as that; I would say rather its more an issue of there being more bass or much less bass. I do care about quality, but right now I'm facing a much larger order of difference: if I can't even hear the bass note it's hard to tell how well-defined it is ;-)

Anyway, thanks for comments!

You could google Auralex or Gramma or SubDude.
You could search at or or
You could read my review at

Kal: thanks for your response, I did indeed google Auralex, thanks for reference. I wish my problem were as simple as a resonance, which would manifest itself, perhaps, as a booming or suckout in certain frequency bands. My problem is more across-the-board, covering a broad swath of bass frequencies. This is a hybrid speaker design where the electrostat panels really depends on support from the woofer/bass subsystem, which it is not getting unless I put the towels underneath.

Note that I have been talking to the manufacturer of the speakers and I believe my issue is... unique and not something pervasive. But we don't know what is going on, it's apparently very odd behavior, and any ideas anyone might have would be greatly appreciated. One theory is that the two bass drivers in each cabinet have been internally wired out-of-phase, but given extensive factory quality assurance, this is seems highly unlikely.
You can test for a polarity error with a bassy mono source by trying it with normal wiring and with one speaker reversed. The correct polarity will give a summation rather than a cancellation of the bass.

Floor resonances are usually wide-band since the surface consists of many planks with different characteristics loosely coupled to each other.

I cannot think of how the towel is having an effect unless it is damping higher frequencies that should not be coming out of the woofer.