Vibraplane vs. Minus k for Turntables

Hi Larry,

I have a Minus-k BM-8 system that supports my TNT Mk.? (upgrades of various vintages). Performance is extremely impressive and I especially like the maintenance-free aspect of the isolator. Although I have no experience with the Vibraplane per se, I have professional experience with similar isolation systems for electro-optical instrumentation and atomic-force microscopy (I'm a biophysicist). You can expect significantly better performance from the Minus-k BM-8 than is available with passive air isolation due to the fact that the BM-8's resonant frequency of 0.5 Hz is at least a factor of 4 lower than that of the Vibraplane. What this translates to is 99% isolation at 5 Hz vertical frequency versus 50-75% for the Vibraplane (depending on load and air pressure). To get better performance than this using an air table requires some sort of active isolation, which is not worth the trouble or expense in my opinion.

I'd be happy to tell you more offline, so feel free to send email to me directly.

I am using the Promethean Base. 100% effective. Brings the resonant frequency to below 2 HZ which is more than enough. You wont' easily hear a difference w more. Last of all, it is much less expensive than either.

Negatives, not a convenient to use as it wobbles (that is why it works) and it is DIY job.

All are a must I depends on you. Go after the Promethean 1st and use it elsewhere if you want to try something else.

I'm not sure what's meant by "100% effective." Whether f0 = 2 Hz is enough depends on specifics. In my case, I live in an 80-year-old house with suspended wood floors and there are plenty of ambient noise sources near 5 Hz, e.g., washing machine, outside traffic, etc. As for not hearing the difference, one can experiment with the BM-8's resonant frequency by manually adjusting the suspension's stiffness with an Allen wrench. I could hear a significant change in the sonic character of LP reproduction - mostly tighter bass and improved image stability at lower f0s. I haven't yet brought home an accelerometer/vibration analyzer to correlate the isolator's performance with acoustic power spectra, but probably will do this eventually.