Vibraplane: Should it be loaded close to limit?

Thanks for digging this up Pete, much obliged.

It certainly is an interesting unit. Since my table weighs around 120 lbs, I've also simply placed it on top of the Vibraplane. The active system makes leveling a whole lot easier than the passive version I'd guess - mine maintains level perfectly once you set the three thumbwheels to the correct height (I'm at 3.75 inches for now). The compressor kicks on once every six hours or so, so I either have a very very slow leak, or that's just how it functions...comments on the interval of compressor cycles would be welcome. The compressor is a Jun-Air, and is the most silent air compressor I've ever experienced - you only hear it click on and off; I think they were designed for dental offices.

My initial impressions are of a drop in background noise by several orders of magnitude, not a softening of the sound, but rather a very black background. Low frequencies certainly have better control and articulation, especially way down low. My concern at the moment is the nature of the top plate itself - given that it's non-magnetic stainless steel, the same material as the cones on the bottom of my deck, I notice a bit of stridency introduced into the upper midrange, a quality that was absent with my aluminum top-plate sandbox. I'm guessing I'm getting a bit of 'chatter' due to the two equally hard materials interfacing with slight surface imperfections exacerbating the situation. I'm going to experiment carefully with intermediary materials between the deck and the Vibraplane, either substituting cone material or introducing another shelving layer between the two.

At 180 lbs, the Vibraplane is a two man lift to be sure, so haphazard swapping in and out is not on the agenda. It will be a while before I solidify my thoughts on what, exactly, it brings to the table over alternative isolation methods, such as my beloved sandbox.

Palasr, doesn't the top plate have three mounting bolts? I wonder if a different material could be used.

Dan,

The surface has no holes; it's an option. I did think of putting my sandbox directly on the VP, but it was too heavy (around 190 lbs (!)) - we each stood on a separate bathroom scale, and aggregated the results, minus our respective weights. A funny sight to be sure.

I can report some very early impressions. I set up the Vibraplane under my TT with no intermediate slab to preload the unit. The improved isolation results in a more articulate bass with more weight and, subjectively, more extension. There is a more silent (blacker) background and overall drop in noise floor which improves dynamics and very low level detail retrieval. I'm hearing spacial cues which I did not notice before as well as clearer relationships between individual instruments further back in the soundstage. In fact, I didn't really have much depth to the soundstage before. Plucked violins in the background providing a foundation for solo mandolins in the foreground for example never sounded this convincing. They are separate in space, articulate and clearly distinct. Finally, I can play the system louder without it starting to break up during complex and energetic passages.

It did take some time to fiddle with leveling the unit using the hand pump on my passive unit and I can see how the active model with compressor would be more convenient. I don't notice any chatter between my TT and the top plate of my VP as the SME TT has rubber footers and notice no such stridency in the upper midrange.

I would add that I find the isolation to be cumulative. I bought my first Townshend Seismic Sink for under my TT and when I bought a second one, I put the first one under my pre amp. Now my second Townshend is under my phono amp. I did listen to these in stages and each addition improved the sound, and the VP seems to be more effective than the TSS.

After I live with the VP for a while, I will start to experiment with different heights and preloading.

Great feedback, guys! Richard and Peter, I'll be interested to hear your thoughts on auto load leveling and the lack thereof as you guys get more time with these units. I'm interested to know how well each unit holds pressure, and how often they need to be leveled in normal use. A passive would certainly be easier and cheaper to build.

These commercial air springs have stiffer side walls which give them an advantage over simple air bladders.

Richard, can you see a way to add a valve in the airline just before the Vibraplane? I assume there is a pressure gauge in the vibraplane. Closing that after pressurizing may tell you if the slow leak is in the unit or before. Does it bleed off air normally as part of the leveling? I'm not sure the compressor running every 6 hours or so would be enough to build up moisture in the air lines. That is the only reason I would even think about how often it cycles. I also wonder if it could be sufficient to run one off of an air bottle in a closed system.

Don't laugh at the bathroom scale trick. We used to do that with our race cars to set the suspension. One scale under each wheel. Obviously, these were pretty light cars.