Symposium Ulta Shelf under floor standing speakers - Any Thoughts ?

I use svelte shelves under my speakers, which are thinner than ultras, and I have ultras under my amp and DAC /music server.  Like any tuning device, whether it helps or hurts the sound quality is dependent on the room/system and what you are trying to achieve.

My setup is on a suspended wooden floor covered with wall-to-wall carpeting.  Speaker spikes would couple the speaker to the floor, which would act as a sounding board.  By using the svelte shelves, I got a tighter sounding bass response.  I have the speakers sitting directly on the shelves (to most effectively couple the speaker to the shelves, which in turn dissipate the energy in the core of the shelves).  In order to tilt the speaker back a bit, I use wooden shims under the front of the shelves.  It is probably best to have the svelte shelf flat on the floor, but, more importantly, the speaker bottom should be in full contact with the shelf, which I manage to do with my setup.  

By the way, I know someone who is in the business of setting up systems and he uses svelte shelves a lot under speakers and finds that in most instances it helps the sound unless the system is already overly dry sounding.

I have looked into more elaborate footers/platforms, but, not much more than a casual look.  The issue with many of them do involve leveling.  The ones with adjustable height of the feet, like the Townsends, would allow for leveling, but, I am not as sure about whether they can be used to tilt the speaker back a bit, without upsetting the spring/suspension mechanism which probably works best with the speaker completely level. 

The Ultras will certainly deliver a lot of vibration absorption (dissipation of energy as heat), but, you should at least experiment with the effects of raising your speaker that much higher off the floor.  If you cannot borrow a pair of Ultras, you might want to use wooden blocks or something to see if the extra height helps or hurts the sound and to see if adjustments to speaker placement can take care of any issues.

Other options include footers like those supplied by Stillpoint.  A local dealer really likes those footer under many of the floorstanding speakers they carry (Magico, Raidho, and Focal).  These things can be much more expensive than anything else mentioned here, but a lot of people swear by them.