@hilde45 - Are the bases already drilled/tapped for spikes/feet? If so, I would recommend a set out outriggers from parts-express. It will provide a bit wider stance, increasing stability, and provides a good platform for the spikes. The spikes will pierce the carpet and go down to the concrete, providing a nice stable base for your tower speakers. You can still use them if your speakers are not tapped, but you'll need to drill holes for the anchors.
Under my tower speakers -- Isoacoustics Gaia, other options?
I have Ascend towers (45lbs each) on a concrete floor covered in thin wall to wall with an area rug on top of that. I am looking into different footers for my speakers and am curious what people with towers on concrete have tried and liked.
To my mind, something as expensive as Townshend platforms do not seem worth it, as they'd cost about a third of the price of the speakers themselves.
If you've tried Gaia III isolators or other kinds of feet for your speakers, especially on concrete floors, I'm curious to hear your observations. Thanks.