for the readers that mention putting loudspeakers on top of granite, or similar bases: I have noticed that several high end speaker manufacturers have now incorporated that into their current design of floor standing speakers, especially ones with a down firing woofer driver. It can be tuned to that base instead of firing into a variable flooring of cement, tile, hardwood or carpet. Of course those models are pricey!
Vibration Isolation for equipment using granite?
I recently visited a high-end audio salon and in the course of discussions with the owner, we discussed the large number of black granite 18x18" blocks he had against the wall. He said that he dealt with a granite retailer to make them from scrap granite pieces from kitchen installations, etc. He said that all equipment (amps, pre-amps, cd platers, DACs, streamers, turntables, etc.) all seemed to benefit from having them underfoot, even on quality equipment racks. It made me wonder if this was true or snake oil? I have my equipment (except power amp) on a Standesign equipment rack with each MDF shelf resting on small aluminum cones that "isolate" it from the steel frame. Question is, does this just add mass which would or wouldn't dissipate the vibration energy or does it work (maybe on another principal). And would sandstone or marble drink coasters, especially with cork soles) work better? Has anyone tried ay of this? Thanks in advance.
27 responses Add your response
Place your speaker on large blocks of granite. As heavy as possible. So that any vibrations from your speakers are immediately killed by the mass of the granite. Place your turntable on springs. So that vibrations in the room do not reach your pick-up cartrigde and stylus. Place all rest of your equipment on spikes. So that maybe possible external vibrations of the surface under your equipment are minimized. |
It’s funny, using granite under my KEF Reference 5’s made a huge difference. I have tongue and groove oak floors with pad and carpet and I never got them to sound clean and clear. A friend who redid his kitchen gave me a bunch of granite. I cut it down to a few inches wider than the KEF’s footprint and gave it a try with amazing results. Later I added some Isoacoustics Gaia 1’s and they made even more of an improvement. I have since bought some Sonus Farber speakers and while there is an improvement using the granite, it isn’t anywhere near as noticeable as it was with the KEF’s. All the best. |
Because it is readily available locally, I use Sydney sandstone which comes in 600-foot thick deposits throughout the Sydney basin. It is about 4% porous, so it has internal damping properties. It does not ring when tapped! Under my Garrard 301 turntable I have two layers of 2" sandstone separated by constrained layer damping, sitting on a 2" MDF platform. The inner plinth sits on three IsoAccoustics OREA Bordeau pucks. The inner plinth is made of three layers of 1-1/4" MDF with more constrained layer damping. MDF is widely used in speaker cabinets because of its stability and internal damping properties. One day I might replace the motor-board with manufactured stone, also known as acrylic containing stone chips, eg Corian. Manufactured stone has just been banned in Australia because of lung disease issues, though. At least one high-end turntable uses two layers with constrained layer damping in between. I personally believe you usually benefit from adding both mass and damping, but Linn owners are cautioned to follow Linn's advice! |
@cooperdude6: Lots of great comments here, and a link by @ditusa to an excellent article. Here are my thoughts on the subject:
- First, replace the aluminum cones with springs. Cones do NOT isolate, they couple. Sets of four springs from Douk Audio are cheap. - As many have already said, constrained layer damping works great. But first you want to at least get rid of the MDF shelves, which suck. MDF is nothing more than wood pulp mixed with glue, not at all stiff. I put a 50lb. turntable on the top shelf of my Solid Steel rack, the MDF resting on four corner cones. The MDF remained supported at only the corners, the shelf bending all the way down to the rack’s metal frame in between. - Replace the MDF shelves with pieces of Baltic Birch plywood. 3/4" thick, 19 layers of cross-laminated Birch. VERY stiff for a wood product. A layer of Baltic Birch plywood with a second of another dissimilar stiff material (sure, granite if you wish) and a sheet of a constrained layer material (check out WallDamp from Acoustic Sciences Corporation) between them makes a great shelf. And at a relatively reasonable price.
|
Constrained layer is the way to go; I use an HRS platform on a big Minus K isolation platform for a very heavy high mass table (Kuzma XL plus Airline arm). I'm not sure one stone over another is the answer. You can probably make what is necessary if you know what you are doing- I went for commercially available solutions -- works a charm. |
Mass stores vibration [energy] and thus does NOT dampen it. What you want is tuned dampeners (eg springs) on a light and stiff platform (or screwed in, such as isoAcoustic Gaias on a speaker, with the proper version of the Gaias depending on the mass of the speaker). Tuned meaning matched properly to the load. You obviously need a lot stiffer dampers for a 120 lbs speaker vs. a 50 lbs amplifier vs. a 10 lbs turntable. |
I am not arguing that a solid stone rack takes away the benefit of good chassis feet. On the contrary, it can be argued the the better the rack, the better the (best) feet can perform. I am only saying that stock feet will perform better too (for example, on my MA-1 amps, or Aesthetix Io preamp). The rack itself offers much more stability and mass, compared to what I had before. My overall impression is that superior stability and mass translate to authority and precision in the sound. Before, I had a VPI record player needing a lot of tweaks to perform its best, including a Bright star sand box. And even some air in a bike tube. Endless tweaking. I changed to a Hanss T-30 player with adjustable "maglev" suspension. This stands direct on the top rack stone shelf. No looking back. |
Using heavy material for equipment racks does have some acoustic benefit rooted in physics, but using solid material like marble also presents risks if used alone. The theory of using heavy materials is termed mass loading. Adding mass increases inertia, an objects resistance to change in motion. The equipment rack will become more resistant to vibrations from the floor and air because it becomes harder to set into vibrational movement. All materials have a resonant frequency - a frequency that easily sets the material into vibrational movement. Mass loading also is used to move the resonant frequency outside of the audible range and providing damping of the energy. Marble provides a solid flat surface for coupling equipment to the rack so vibrations from the equipment are transmitted to the rack. So why does marble alone fail in theory? Vibration travels through solid material easier than liquids, liquid easier than gas. The marble will be subject ringing and resonant frequencies, and easily transmit the ringing to the equipment by coupling. This will be audible most probably as muddling detail and high frequency distortion. Most equipment racks that use mass loading will use sand, which acts to present the befits of mass loading while also having “liquid” properties to effect changing the resonant frequency and damping. The best vibration management systems combine the use of mass loading and damping. |
@billstevenson Perhaps you misunderstand. When I said that you are totally correct, I meant it. |
I have a huge larvikite stone rack. Similar to granite i believe. It is very heavy and supported both from the wall and the floor, I can jump in front of the record player with no skipping. I have read about stone being too hard and reflective and so on, but so far my experiments have not proved this. I have glued damping material under the stone shelves. This works ok, although not dramatic. Damping on the top of the shelves, or big carpets over the whole rack - not much improvement. There is some effect of different component feet, but it seems that the thicker the stone shelf, the less difference. At the bottom of the shelf are thick stone slabs. It is like my rack is telling me, I can do this myself thank you. |
@assetmgrsc Ah spoken like a true science denier. |
@billstevenson read your response with a smile on my face. You are, of course, totally correct, but let me say it like it is: BS on top of more BS. |
Granite used solely as a Sub Plinth will impact on the perception of the End Sound, but as has been mentioned not to all who have used it liking. My experiences of using Granite, is that I have come to prefer it over other Stone as a Sub Plinth, it has been compared to Marble and Concrete. Where it works best, is when used in a Sub Support configuration as a Tier in a assembly. I usually find Three Tiers with a selection of separator types works very well, and can be produced quite cheap, where the structure offers good impressions, which in my environment can impress similar to much more expensive sub support and footers. If you really want to get the Best from a Single Tier Sub Plinth the material known widely as a Resin Impregnated Densified Wood, will be worthwhile investigating, as a material it is about the best there is. |
I vastly prefer quartz countertop to granite, as being a mix of quartz and acrylic resin it has a much lower Q-factor than granite and greater density than wood - an 18X24 3cm slab clocks in at about 75lbs. Chosen from a local countertop fabricator boneyard, it was about $15 ft2 so $45 plus another $200 for finishing the edges. . Using 2" 70 Durometer Sorbothane feet from Amazon ($22.95 for 4) underneath, my 50+ lb VPI Prime Scout has no acoustic feedback issues. And since I didn't have footfall issues to begin with, I can't comment on those, other than to quote Newton's 2nd Law, F=ma or F/m=a. As mass increases, it takes more force to accelerate it. My rig is at 125Lbs and counting, so it takes a lot or force to excite it, and thats after the sorbothane has damped it. |
Back in the day when I had a TT...30 yrs ago! Yipes! The room I had to work with was NG. Second floor apt in a house. I could easily overpower the room with bass and cause the TT to skip. So, I got the brilliant idea to get some marble headstones (scraps) and have them cut to fit. Two slabs ~19X20X3 inches. I also happen to have some sorbothane ~1" that was used to isolate Avionic gear from jet "fighter" vibrations. Interesting stuff, actually feels like human fat. Very compliant and then not! Fat story slim. One slab on the bottom then sorbothane then other slab then TT. It completely stopped the problem I was having. Much to the angst of the landlord downstairs. YMMV. Just one guys tale. Regards, barts
|
All great replies. Thanks to all. I guess everything may have it's time and place, but no solution for all applications. To my ears my system does not suffer from any ringing or excess vibration issues to warrant tinkering, but each situation is different. I was just curious if his approach is justified. Now I can understand a heavy slab on top of a component, but with ventilation considerations that is probably not practical. |
I used as mulveling said a sandwich of different materials with success... For stability reasons i stop using springs , my actual speakers being small desktop Edifier... But i go on again with absorbing special properties(low cost) bamboo plate, sorbothane, granite plate and concrete block... This coupling /decoupling work well especially with the fine tuned right amount of concrete block over my speakers for damping them..
|
When I’ve tried 1" slabs under speakers it made the sound brighter and harsher, which I didn’t like (yes, this was a lazy ham-fisted attempt with just hockey puck footers). Didn’t find it worthwhile under components either, and they’re a PITA to handle at that size / weight. However HRS has used thin slices of granite in combination with dissimilar materials (constrained layer damping) to apparent success - but that’s quite different to a singular slab of granite. You should consider using it in conjunction with something like sheets of Herbie’s grunge buster or generic sorbothane to control the ringing. Full coverage (thin sheet) is much more effective than just footers.
This gels with my experience - the interaction between support structure (rack) and turntable suspension / plinth is going to matter a lot more than anything else, for some systems. Those on concrete slab can get away with much more here. I’ve had turntable & rack combos resonate in the audible bass range (really bad), in the subsonic "woofer flapping" range (REALLY bad - most rumble filters don’t attenuate this enough), and in the relatively safe sub-2Hz range (SOTA). |
One must be careful when using granite or other solid rock. They ring and they transmit energy through them very efficiently. So you would not want to use cones under a granite slab on a concrete floor. You would be transmitting the energy directly to the components. On the other hand, the mass is an advantage. So, to get the value without transmitting vibrations the slab needs to be isolated. So for instance elastomer pucks or Vibrapods under can isolate them from small vibrations. For my amp, I use an amp stand, with vibrapods on top of it, then the granite slab and springs on top of the granite. Mass works to my advantage here. But even better, as I use under most of my components are vibrapods on the rack shelf, then Black Diamond Racing platforms (very dense composite... really heavy), then springs on top of that, then component. This is a fairly slim profile. For my turntable I use a custom Silent Running Audio Ohio Class vibration platform. These guys make vibration platforms for electron microscopes and other really critical applications. It had a very significant effect on my Linn, Klimax turn table. I would say this is the highest level of vibration control, Townshend platforms are also transformative for speakers. |
I would say neither true, nor snake oil. I use granite slabs under my amps and under one of my turntables. I find a subjective improvement in quietness and contrast on these. But I would say, as with so many things in the sport, a try and see kind of thing. We all hear a bit differently. I try to avoid speculative theory, but I believe the primary resonance frequency of the support is more important than the speed of propagation in the material. And this particularly true in turntables where the suspensions are tuned to different frequencies. |
Sound transmits better as the density of the molecules of the medium it is traveling through go up. Hence sound travels through water more efficiently than through air, and logically through solids more efficiently than through water. That is basic physics. Any mechanic can tell you that using a long handled screw driver, handle against ear, blade against malfunctioning mechanical noise (such as failing bearing), is very helpful in isolating the location of a problem on an engine for example. Yes he/she can hear the knock, but locating which bearing is failing that is harder. So, back to the granite blocks, are they solid? As such and understanding physics, do you think they would be effective acoustic isolation barriers? |
