Improving a stone rack

springs

Having a little fun: Maybe not grandma's tablecloth, but you get the idea. Keep your stability, add some softness on top

Depending on design, you may be able to place sorbitans spacers (buy sheets or strips) between the granite and whatever is supporting the granite. Then do the same between the supports and the floor (cover the sorbitans sheet that touches the floor with felt to protect the floor if the floor is wood).  

I built a "rack" from three 20x40 inch black granite "shelves" and wood supports (hard maple 2x4s glued together for the uprights and 2x4s for the cross supports, the granite is "inserted" into slots in the wood.  Everywhere the granite touches is covered by the sorbitan, and the upright supports have sorbitans on their bottom surface covered by the felt.  I choose the thickness of the sorbitans to not only support the weight, but for the harmonic frequency that needed to be absorbed.

Incidentally, different granites have different harmonic frequencies.  Apparently black granite is the best for audio applications (eg see Acora speakers).

No "ringing", no vibrations, incredible stability.

+1 on IsoAcoustics under your gear.  Probably the easiest and most effective solution for any vibration issues your gear may be subject to.  Next, I agree that if your rack is between the speakers it can contribute negatively to the sound.  Consider yes, thick cloth but also short acoustic panels on the side and behind the rack itself.  Also, given the angles, room treatment on the ceiling between the speaker and listener is always a great idea.

I have a granite amp stand. I found it effective to place vibrapods (there are many alternatives) under the granite to isolate the slab, then springs between the component and the slab. So, micro vibrations do not get transmitted into the slab from the floor and the component is isolated from the slab. Obviously a vibration platform would be even more effective than the springs. 

I usually improve stone by getting more stoned. Works for me great!

I tried a granite slab under my turntable a few years back and it had a considerable negative impact on the sound quality.  I tried it in three modes—alone on top of the concrete block pillars (see virtual system), on top of, and below, a 3" slab of maple. The poor sound was present in all three modes. It was a relief to remove it. My back was not happy. I was amazed at how poor it sounded. 

I have experimented with isolation materials. Hard surfaces like granite, glass, etc is going to emphasize the treble freq. Soft material IE Vibrapods, sorbothane will soften the highs but often at the expense of clarity. Muddy sound come to mind. A tone wood IE maple is the best I have found. I've also used DIY roller ball  type footers with good result. I recently changed from those to springs and saw no degradation to the sound.

I have used Granite for many Years as Sub Plinths for Audio Equipment on Racks and as a Cabinet Speaker Sub Plinth.

I find I prefer the sonic that has been created when using it, when the Granite is a Sub Sub Plinth or a Sandwich Material in a Build up of Materials to create a Plinth or Sub Sub Plinth.

For Speakers I always uses a Spike Coupling and Pneumatic Footer to create some suspension.

On the equipment Rack, I always use Cork as the Isolation footer for the Granite when in a Sandwich or as a Sub Sub Plinth.

Other Materials used in conjunction with the Granite will have  a selection of Footers tried out to discover which tidies up the sonic to a standard I am happy to experience.

Today, my usage of Granite is seemingly being superseded by the use of Phenolic Resin Densified Wood Board Materials, such as the Board Materials from the Brands Permali or Panzerholz.

I recently bought a rack from Acora audio and the shelves are African black granite. The underside of the shelves have some type of anti-resonate material attached to it. I always wanted to upgrade from my 20+ year old Target rack. I was thinking about the aesthetics of the new rack but the improvement in clarity, resolution and musicality has taken my sound up a few levels. I had my doubts about buying a granite rack but when it’s done right, it sounds great. Try reading some info regarding Acora’s racks, you might get some insight on what to try.

Try using a very dense wood that has a totally different sound signature from the hard granite in conjunction with the granite.  I've tried many different types of materials for a rack.  I have been using a pair of Sistrum racks from Star Sound for many years.  Anything that is placed on it immediately sound more live but without ringing or any other sound issue.  I also use RTS couplers to clamp each component to its shelf.  The combo is about twice as effective to improving the SQ as the Sistrum rack alone.  I was very lucky to have a former owner sell me all his Sistrum racks used at very good prices.  You can even install this racks between the speakers with little or no drop in soundstage info.  My two racks are about 18" behind a line between the two speaker fronts.  They allow so much air to circulate w/o ringing vibrations behind heard it's wonderful.  Used they are MUCH MORE affordable.  Thanks Al Jennings.

Bob

“African black granite” is not granite but instead fine grained gabbro. It’s denser than granite, as different minerals make it up. No quartz, and denser, more calcic plagioclase feldspar, and relatively dense, iron rich pyroxene. I am retired now, but I was a volcano guy and used to analyze igneous rocks. Catchy trade name, though. I agree that this material really works for speakers, as all the Acora speakers I have heard are really special. And the owner is a truly nice guy, who I am delighted with for buying Audio Research. 

@jallan I’m not as well versed on granites and types of rocks as you, just going by what I was told. I don’t doubt anything you’ve said. I definitely agree that Valerio Alcora is a very nice guy and great rep for his company. I emailed the company with a question regarding setting up the rack and he actually called me himself and walked me through it. This rack weighs about 250lbs w 5 shelves and definitely improved the sound. 

I remember the first time I heard his smaller speakers-it was 2017. I was more impressed by the sound that they were making than anything else in the Capital Audio fest. Of coarse he was running Audio Research gear- Ref 6 preamp and the 75 ref amp, and it was glorious. And honest guy. It was the real deal. If I could afford it, I wouldn’t hesitate to buy from him. I have just never heard any real flaws in his products, they sound fabulous.

Granite rings.

Could it be your gear sounds hard?

Easy, isolation under each gear. I don't have stone racks but do it nevertheless. They are plenty of choices, springs, soborthane, isoacoustics, etc...

I don't think your rack is affecting the sound, but if throwing a rubber blanket over it makes you feel better then go for it - it's not as wacky as the power cord or magic UEF people.

Thanks for suggestions! The winner so far is grandma's tablecloth!

I will digest and absorb your wisdom. But before we go further: Is there a METHOD to the madness? I mean, I have a suspicion that my stone rack is adding some hardness and extra treble to the sound. Some of you say yes, others no. But what can I do, to test if the hypothesis is true? Maybe the rack problem is very marginal, the hard sound is mainly due to - for example - my somewhat hot tweeters?

Here are some ways I have tested. 1) Hand clapping in front of rack, vs other parts of the room. Result? Not conclusive, perhaps marginally more echo. 2) Listening with a stethoscope on the stone shelves, while playing loud music. Result: cannot hear any clear ringing. They ring when I strike them with a hard object, of course, but not sure if it plays a role with music. However the large volume from the speakers makes it hard to hear whatever goes on in the stethoscope. 3) Varying the basis of the shelves by dampers on the steel supports. Some effect maybe but not a lot, and it lowers stability so again, not sure. 4) Using a variety of footers, including Cerapucs, Walker valid points and large ceramic cones. Some effect, yes, but not so great as I first thought. It seems that the more massive the stone shelf, the less is the extra bonus of good footers. I have some massive stones at the bottom of the rack, and have a tendency to think "i don't bother" with footers there. 5)  Try to measure, using REW. So far, not very helpful.

Other suggestions for method are welcome. I know what some of you may answer. Just throw a huge sound-damping cloth over the whole rack! If I don't hear a clear improvement, the "stone rack is bad" hypothesis can be laid to rest in my case. I will consider it.

Try placing a Peel and Stick Vinyl Floor Tile on the "bottom side" of one of the granite shelves.

I’d start with a source component shelf.

DeKay

I'm not a physicist or engineer however, I do read what those experts have to say about things. One of the major keys to damping vibrations is dissimilar materials. If you GTFS "vibration damping material" and check out the images returned you'll see what I mean.

Your stone rack surface, while rock steady (sorry!), also serves as an almost ideal coupler for vibration. By introducing a dissimilar, flexible, material you should be able to ameliorate the vibration/ringing situation.

Happy listening.

@jallan 

I wonder which gabbro complex they got it from, Skaergaard, Bushveld, Muskox, Duluth?

Townshend can fix it for you. Whether it’s pods or platforms it’s one and done. Most recommend isolating each component which is expensive. Maybe start with a source and see if you get good results and continue if it works for you. Townsends isolation platforms and pods have been my best solution. 

@o_holter Are you assuming the shelves are ringing or reflecting the sound waves coming from the speakers, and adding a hardness? While that is valid, it’s not a major contributing factor. I’ve always thought of the challenge being more to do with the relationship between the supporting material and the component itself. It’s at that interface where the support-related sound quality is generated. Vibrations generated by an undamped extremely stiff material coupled by spikes, cones, or footers to the component causes that hardness. The corollary is that soft materials like cork or pine damp the vibrations and soften the sound. I’m not sure why exactly this is the case. However, assuming it is the case, the best way to ameliorate the effect is to decouple the component from the surface. I use Nobsound springs ($29 for set of 4 on Amazon) Not only does it fix the hardness, it adds dimension and speed to the music with blacker backgrounds.

Edit: It's worth an experiment and a lot less expensive than the Townshend solution mentioned above in the time I took to write this!

@ghdprentice 

I don’t think it’s quarried from those bodies, but sounds like you are a geologist!

This might be a good guess:

https://wap.stonecontact.com/africa-black-granite/s2563

South African Precambrian gabbro, it certainly looks like the rock of his speakers

Yes, I was, my first career. Lots of folks from the department went to Skaergaard. This was in the mid 70s when they were just unraveling the sedimentary features of the crystals inside the chamber. Crystal turbidities and the chemical differentiation / substitution inside the Felspars, olivine, and melt etc.. I was at the U of O where lots of this research was going on.

But the first gabbro complex I used to climb around on was the Duluth Gabbro Complex. You just never forget your first gabbro complex.

I was fascinated by peridotite. And then, of course, serpentine exposures around the world. So my countertops are all serpentinized peridotite now.

I share experiences with others, whereby adding granite slabs under components or (especially here!) speakers has had a significantly deleterious effect on sound quality. Harsh, bright, brittle sound. Just awful. 

Of course there are also known quality products where granite slabs / sheets have worked wonderfully. HRS incorporates granite in their platforms. Acora speakers (granite cabinets) sound awesome. I've got a friend with granite bases (sandwich design) for his Vandersteens - works great.

I think the most common theme for success is that damping needs to be applied over the full granite surface (at least 1 side). Iso Acoustics feet on 4 coroners isn't enough - I even tried that with my speakers and the granite slabs - no help. 

Herbie's sells (no idea of current availability) his "grungebuster" material in sheets cut your needed size, and I believe that's what my friend suggested for use in a sandwich with granite platforms. Seems reasonable to me! At least cover the top of each rack shelf, in your case. 

I'm looking to use a glass shelf rack, 5 shelves that sit in slots in the wood frame with a soft vinyl supporting the shelves. A Technics 1500c tt will sit on the top. If anything, what type of damping would work well on a budget? I was thinking of the stick on felt pads that you put on the bottom of chairs so they don't screech across the floor attached to the feet of the components. Too simple? How about an old tt mat cut into pieces?

Granite (sorry!)  I don't know how bad the rack is but it's probably not great. The turntable on top is probably the worst location, especially if you're on a suspended floor. Anyhow, try it all out first and worry about damping then. Otherwise you won't know if you've improved things. 

@ghdprentice 

I must correct myself- I think you’re correct that this stone comes from the Bushveldt Complex in South Africa- I just looked up the location in Google Maps!

My stone rack is made of Larvikite, found near Larvik in Norway, sometimes marketed as Emerald Pearl, or Blue Pearl. It is even claimed to be a Norwegian ‘national stone’ (though it is found also in Canada). I am sure that helps with the sound!

@noromance – yes, Nobsound springs may be interesting. I will first try my big Walker audio Valid points under the preamp, to see if they make a difference. Cerapucs might be even better, but aren’t high enough beneath the preamp to take over from the stock feet. You wrote:

«Are you assuming the shelves are ringing or reflecting the sound waves coming from the speakers, and adding a hardness? While that is valid, it’s not a major contributing factor. I’ve always thought of the challenge being more to do with the relationship between the supporting material and the component itself. It’s at that interface where the support-related sound quality is generated.»

Yes, I assume that the polished glass-like shelf surface plays a role. Somewhat like windows, changing the sound in the room. Although I don’t think ringing is a main problem. I would probably have to play music a lot louder than I do to achieve that. The rack is massive and inert.

I agree that the component / support relation is important. But how can I know if this is the main factor? Rather than reflective surfaces? These should be manifest in two different sound problems, no? In the direction of ‘glassy’ (reflection), and ‘smear due to vibrations’?

Small test result. Walker Validpoints under my preamp, compared to the stock feet, resting on the stone shelf. NB I am not able to do quick A/B comparisons. The preamp is too heavy and my back too poor.

First impression: this is larger. More distinct. But less treble, or softer treble? No. And softer more mushy bass? No not at first, at least. So the first test, plus one for Valid points, but with some unexpected results.

The Valid points are three large and heavy brass spikes that go into damping discs on the shelf. They rise the component and are undoubtedly good for ventilation at the bottom. Sonic results? Not sure yet. But I am sure these footers do something, they do have an affect. Walker have thought about this.

My Einstein The tube mk2 preamp is a one-box design with two massive power supplies in the front, and tubes at the back. A hybrid tube/s state design. The s-state power supplies get very hot, and I guess, these are the main cause of vibration (even with top German design). So I used two validpoints, one under each transformer, in the front, and one in the middle at the back. We'll see, if this works out. Like I said, my first impression was a bit mixed.

Second opinions are important too. Testing Oops, by Fujiya & Miyagi, from their LP Slight variations. A career height I think. With the stock feet it sounds good but bass heavy and somewhat restricted. With the Validpoints, it sounds larger, the timbre is mor convincing, the sound comes to life. Great, but there are some minuses also, some treble stands out too much, and not fully sure about the bass. The validpoints came with some extra tuning discs, placed on top of the components, to cure such ills. Have not tried yet.

I have a very dead/dense/heavy pair of hand crafted steel framed stands (filled with sand/shot 50/50). The top has 1" thick non-Gabbro granite shelves/plates (polished and beveled) mounted on silicone footers. I have no problems with various rubber soled equipment (EAR pre-amps, Zesto SUTs, a pre-amp that had thin aluminum base using Stillpoint SS footers, etc). I do have a problem with an EAR 324 phono pre which sounds best with a buckwheat pillow under it. My VPI VI turntable always sat on a 1.25" thick HDF board on top of a Townshend Seismic Sink (terrible footers on the table).

Below, I replaced the thick tempered glass shelves with silicone bumpers with 1.25" HDF mounted on Blu-Tac which appears to completely deaden the already dense wood. Maple/butcherblock would have been an alternative.

I have a tempered glass rack that does emphasize the highs and makes everything sound a bit "sterile" and cold.

I solved the problem by having my electronics on some bamboo cutting boards (Ikea Aptitlig) which themselves rest on 4 Moongel pads (the stuff used by drummers to dampen their drums). Works a treat and I don't hear the mushiness normally associated with soft stuff such as sorbothane.

After reading a lot of posts on Nobsound springs, I have decided to give them a try, and have ordered three sets of four. @noromance and @millercarbon helped me make up my mind. Basically I warmed up to the idea that you need a vibration-free stand AND vibration devices. So, we'll see. It will take some time before they arrive.

My speakers are sitting on the actual Duluth Gabbro Complex, they sound very good. 

@rolox wrote "I have a tempered glass rack that does emphasize the highs and makes everything sound a bit "sterile" and cold." I understand what you mean! Springs (like Nobsound) most probably won’t solve all of that, but hopefully, help reduce it. It is one of my three strategies: damping component vibes (better feet), damping reflective surfaces (shelves and back wall), and damping the shelf bottoms with absorbant mats. I realize I have an Ikea Apetitlig in our kitchen, and should try it.

@fleschler - my VPI hw19 experience was the same. It needed good feet and even a sand box platform. And the springs needed very careful ’just so’ tuning. Interesting that your phono pre is the one where you noted problems. It is the most sensitive component in my rack also.

A learning experience

I have a Meade ETX125 EC astro-telescope on a tripod stand. I use it on two types of foundation: solid ground (outdoors, not very convenient), or a wood veranda (convenient). Guess what happens. The solid stone ground totally outperforms the wood. The image becomes stable and clear, while the veranda image remains blurred and shifts if I move or walk on the veranda.

I wish things were this clear, in audio.

With the telescope, either I see a crater on the moon correctly and in focus, or I don’t.

In audio it is more - maybe this, or maybe that.

If I should create a new laboratory with precision instruments, e g electron microscopes, what would I do? You guessed right. A combination of total stability and well-tuned component damping. Maybe even springs on stone shelves.

For a Telescope there are also a Tripod Footer that will further absorb energies in the Slab and should give a further improvement to the resolution.

Some even put kiln dried sand in a Bicycle Inner Tube and snake it around the Body, this is also a trick used in the past to improve resolution.

IS is a advancing modern concept as a design and will remove the need for some of these old tricks.     

@o_holter Is your phono pre also solid state like my EAR 324?   When I used the EAR 864 and the 912 which are both tubed phono and preamp combo, they sound best on the granite on their own feet.   My HW19-4 is used for 78s now and it has a superior spring and rubber footer (a sprung table) compared to the lousy Delrin VPI VI feet (unsuspended).

@pindac - thanks, I have the original Meade tripod, with no internal damping that I can see. Snake it around the body - you mean the telescope? And - what is IS concept design?

@fleschler - my Aesthetix Io is a tube phono. I think the newest version comes with HRS footers. I cannot experiment with feet under the main unit, due to lack of height in the rack, so it is nice to know that tube phonos can sound best on their stock feet on granite. When I get the Nobsound springs, I will test them under the two power supplies of the Io (there, I have enough height).

'IS' is in relation to optics - Image Stabilisation

Yes - The Telescope 

For Static Tripod, I adapted a Hollow Tube Civils Engineer Surveyors Tripod.

I stripped the Tripod back to singular parts, plugged the bottom of the Tubes/Forms and filled with a Liquid Rubber.

The deadness of this design is substantially attractive, but quite heavy, hence the remain in one place usage.   

@o_holter There is a pretty good reason Jim White uses HRS… lose your feet and try 3-4 short HRS Nimbus couplers under your Aesthetix….. i’m up to about 20 of them across 2 systems….

For those who dislike Granite, try two 1” or so slabs w green glue between…. welcome to constrained layer damping….on the low end $.

One thing leads to another...

@pindac - thanks, interesting, I'll try to check out some more when I go to the cabin with the scope in some weeks. Must also find some way so it can stand outside even with rain. Image stabilisation - yes, even my phone camera has it...

@tomic601 - yes I know J White prefers HRS and I have reasons to believe him. Problem is, unless I change my rack setup, the Io only has space for very short (stock) feet, to get enough ventilation above the chassis.

Constrained layer damping - well, I have adhesive damping mats under some of the stone shelves. Result? In the "yes maybe" direction - no harm, but no big positive effect either. Typical of my attempts to improve the rack.

Hello OP,

Granite is both reflective and absorbent depending on the material science and finish. The frequency of the shelves vibrating adds to the overall sonic in the environment. It creates additional noise elements or rack chatter. This effect also transfers into the electronics package, producing inefficient component operational performance and affecting their sonic.

I recommend placing a resonance conductive metal or alloy material on top of the granite shelving below the component. Thickness is relative to material selection. This addition will reduce the sonic signature and frequencies of the shelving while establishing a rapid sink for resonance flow. 

The material selection is critical due to natural damping factors related to the materials.

Rubber and cork dull the sonic in components via absorption. 

Springs suffer from spring fatigue. A small amount of fatigue delivers an audible loss in the leading edge dynamics. They are affected by weight, and the design wears out and should be replaced with new springs routinely. 

Decoupling defies the laws of gravity and is a word established by the Audio Industry to sell more products.

I recommend adding component footers after the rack function has improved and installing versions that match the overall design methodology.

We are willing to assist with overhauling the design without charge should you want to turn the granite rack into a performance-driven platform. 

Feel free to contact me.

Robert 

LiveVibe Audio

Hi Robert / audiopoint, very interesting, much appreciated. I took a look at your web site also. I agree springs can be tricky, soft materials not good, etc. The idea of metal or alloy under the components seems relevant and should be tested. At the moment I am testing for reflected treble from the rack, using thick wool carpets in front of it.