I knew for some time as a matter of resonance hygiene that I needed some further treatment to isolate my SME 30 turntable. My sound has been generally excellent, and through laziness I just never attacked the project except to look at options from time to time.
The SME 30 has a robust built in suspension. It utilizes two stacked high density horizontal plates separated by rubber banded suspension pillars. It also has some isolation in the feet, either a choice of silastic inserts for soft surfaces or spring loaded ball bearings for hard surfaces. The theory is that the dense horizontal plates drain the vibrations from outside and inside the turntable into the 3 Hz tuned oil filled pillars. I had the feet placed on the silastic inserts on an older Nuance platform (no longer made, manufacturer didn't find he could make them cost effectively) on top of an end table.
I also have a concrete slab foundation, which theoretically takes care of vertical vibration components.
I do not use an audio stand for the turntable, but a sturdy end table, not high end as the photo shows.
Anyway, the resonance performance can be tested by turning off the turntable motor and lowering the needle onto the non-moving vinyl surface, and turning up the system volume, and tapping/ thumping at various locations.
In the PREVIOUS set up, tapping the top plate of the SME 30 resulted in a big thump through the system, as expected, tapping on the platter, vinyl, or top horizontal plate itself.
Tapping the "isolated" horizontal lower plate, separated from the top plate/platter by the pillars, resulted in a lower by 15-20db (ear estimate only, not measured) thump, indicating the feet isolation at work.
However, to a lesser extent, thumping the end table itself under the Nuance platform would also result in audible feedback. That is where I knew I needed some resonance hygiene. I have four subwoofers, and I like the bass hot and heavy, I can feel my body vibrating on playback, so I assume the turntable/stand can, too!
A resonance platform would need to hold the 100 pound weight of the turntable array.
These granite isolators are made for laboratories utilizing microscopes, lasers and sensitive weighing instruments, NOT AUDIO. They use some kind of specialty, hi tech silicon damping compound under the granite on a plastic shield. My sample arrived perfect. The granite is beautifully finished with nice 3D crystal, as nice as any high end granite countertop. My 16 by 21 inch model, for 140 pound weight, is about 1.6 to 1.8 inch thick. It weighs about 36-40 pounds. The 16x21 model retails for about $1000 sans tax/shipping. I managed to find a used one for $350. They come in several sizes and prices for different loads and sizes of objects. The silastic is supposed to be extremely durable, in excess of 20 years of life.
The manufacturer does not imply or suggest that these are substitutes for heavier and more elaborate air pressure isolation units, but says the are good for microscopes up to 1000x magnification. The manufacturer also says the use of the Granite Isolator in conjunction with air units will improve the air units' performance.
The Granite Isolator must have some limited self leveling and weight distribution, because after putting it under my Nuance/SME 30, the bubble level was perfectly centered without adjusting the feet of the SME 30.
Anyway, AFTER placing it, the tap tests ABOVE the Granite Isolator went as expected, with audible thumps from the top horizontal plate/platter, just as before. As expected , an attenuated thump from the lower plate, and even a bit more attenuation thumping and hitting at the newly placed granite surface above the isolation elastic pads.
However, robust thumps, knock, slams, opening and slamming the drawer/door etc beneath the elastic pads on the end table support resulted in silence. The Granite Isolator beneath the elastic pads effectively decoupled the wooden end table from the turntable array nearly completely as far as I could tell. No more thump there. Before the placement of the Granite Isolator, thumps to the end table resulted in highly audible feedback through the needle perched on the vinyl on the platter.
Trying to estimate the effect on the internal drainage paths of the turntable or the change in the fundamental tuning frequency of the array would require instrumentation and I don't have those.
Wiggling the Granite Isolator with the SME 30 in place, I would guess the horizontal isolation frequency at about 2-3 HZ just by watching it dampen over about a second or so. The vertical frequency is harder to estimate because it is difficult to observe.
As far as the subjective listening, I would say there is a noticeable improvement in bass definition as well as general clarity of the image THROUGH bass heavy passages. This results in a better CONTINUOSNESS to the music presentation. Given that it is perceptible from an already high performance system, I would call this reasonably impressive.
Another more subjective and less credible impression would be a bit of added upper midrange gloss to the presentation.
How the Granite Isolator compares with air units or spring units like the Minus K, I have no idea, I would imagine those sophisticated air or spring types would have some advantages. However, they also seem finicky as well as expensive. The vibraplanes (except the ELpF model) are extremely heavy, they require some monitoring with compressors, and anything with air and bladders tend to be subject to deterioration and lifespan problems. Having used compressors for decades in my profession, I am not the least bit interested in having them in my audio system.
The Granite Isolator is not cheap at it's retail price, but neither is it outlandishly expensive by audiophile standards. The Granite Isolator appears to be very effective, and is easy "place and forget", kind of like the SME 30 itself. The price ranges between some of the cheaper Townshend products and the much more expensive Vibraplane/Minus K types isolators. The Townshend products seem to be objects of relentless complaints concerning reliability over time and the air bladders being hard to manage or failing.
The Granite Isolator is worth considering for heavy turntables in the 4K plus price range in a care free oriented vinyl system, even though it is NOT an audio product. If it can offer improved resonance hygiene for a sophisticated, suspended turntable like the SME 30, it must be decent and it is pretty, to boot. I presume they can be used for any type of resonance sensitive type audio product as well, such as heavy tubed amplifiers, etc.