Hi Tompy
I asked about the disks - they were there to get the tweeter height up a bit to improve the sound heard by the second and third row of chairs. Ideally a plinth should have been used.
Because we mount our bass drivers in a reaction cancelling arrangement, spikes have no effect whatsoever on our speakers. No vibrations are transmitted to the cabinet and thus there is no need to couple it to the ground as spikes do. We provide spikes mostly to aid stability on carpets and also obviously because most people want them, but they provide no acoustic enhancement.
The other interesting thing about using reaction cancellation is that because there is no vibration transmitted, our cabinets can be made lighter. This is hugely advantageous as the heavier your cabinet is, the lower the primary harmonic resonance. The lower it is, the more likely it is to be excited by the bass drivers which possess the highest kinetic energy of all drivers. Making the cabinet light allows us to push this modal frequency up, further and further away from the highest energy source and therefore avoiding this common cabinet problem.
If we didn't cancel out the driver reactions, we would be forced to make the cabinets heavy, and thus miss out on a really crucial advantage, one that really benefits the acoustic performance .
Next time you play Vivid speakers really loud, put your hand on the cabinets and appreciate just how "dead" they are. They're not contributing to the acoustic waveform and since they have a lot of surface area, even a small contribution can really mess with the intended output.
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