While doing some deep thinking, and noticing that there are a hell of a lot of cats around here,and that they tend to manufacture themselves, I came up with an idea for an even better system of damping.
I found that cats, properly drugged, are excellent passive dampers but,even better, they make superb active vibration dampers under things like CD-players turnatables etc. What I tried was using a motion sensor feeding an op-amp circuit that in turn sends the signal to the Feline Motion Feedback Circuit.
When the motion sensor detects low-frequency vibration (under 200hz) it sends a signal to the op-amp which then sends a counter signal to the individual Feline Vibration Units. So, for example, if the motion detector senses the shelf moving up due to the positive side of a large bass note, the signal is sent to the FVU to move down thus cancelling out the motion of the shelf. Due to the FVU natural quickness I figure that the system can be actively damped up to 200hz.
There were, and are, a few bugs to work out of the system though. One is finding 4 cats of equal size; it is hard to system level bias when the felines are not of equal height. The other problem is getting cats of equal age and neural response; older cats seem to respond less to the Feedback signal. These problems were both solved by the use of the Feline Individual Bias System (FIBS for short).
A DtoC (Direct to Cat) voltage is applied to each individual Feline Unit to establish proper level adjustment. Of course, having four balanced Feline Units is best but raises the cost somewhat.
The other problem was the sibilence occasionally heard during testing. This was solved by the use of more, and better, drugs. (As is usually the case.)
The results were really quite good but only up to about 200hz; after that the inertial mass of the turntable prevented any response. So, it being obvious that the Single-Ended Feline Vibrational Units were not powerful enough to respond, I tried the Push-Pull system. In this system the four FVU are set under the load as in the SEFVU but we now add four units on top. These are wired counter-phase to the lower unit so that as the lower unit goes up, the upper units go down. And so on. This raised the response frequency to about 1khz.
This system works very well and even small earthquakes are dampened out. The sound quality is vastly improved. There is now a smooth,silky sound on the mids and highs (except for the earlier sibilence). Bass is solid with a quick,rhythmic reaction. One gets the feeling that the bass is ready to spring at a instant!
I did run into a small problem in my early tests: My neighbor, wondering what the hissing was about, came over to see my experinments. Unfortunately he brought his dog with him... After spending 2 hours getting my turntable out of the tree, I thought it prudent to up the drug dosage. There have been no further problems.
The FVU work well with cd-players and turntables but I found that they are too small and light duty for the subwoofer; they had a tendency to go into spontaneous vibration and then collapse. I am working on a substitute.