The Effect of Damping on Sound: Racks and Turntable Plinths

[WeatherB]

Hi Bruce. Sorry for jumping in late, but are you saying that you are experimenting with shelves that are different from the ones provided by Adona? I thought Adona already used a CLD like multilayer shelf solution?

Hi, Tony
Yes, I have been using different materials for shelves. Still experimenting, but I have had some seriously positive results.
The Adona shelves are a made from a thin layer of granite on one side and a layer of MDF (I think) on the other. They are bonded with a material that is said to be great at damping. Make no mistake, the rack is fine as-is. Until you get above the $10K price point, I think they are the best alternative on the market.
But what I have found is that the shelves can be improved upon.

To date, I have used in various combinations:
Bamboo boards
Maple boards
Granite (1 1/4" thick)
Delrin (1/2" thick)
Carbon fiber sandwich platforms (1/8" thick)
Gingko platforms (I have a springy, compliant floor)

Isodamp (1/4" thick and 1/8" thick)
Sorbothane washers (50 durometers)

Let me know if I can answer any more questions!

-Bruce

 

[PeterA]

Bruce, can you describe the effect of isodamp? And did you just use a straight sheet or was it in conjunction with another shelf material?

 

[WeatherB]

Hi, Peter

The effect is somewhat like using properly positioned Sorbothane, used as intended, only more so. The noise level audibly drops allowing you to hear more complex and subtle nuances in the fabric of the music. The noise floor is lower as well. One thing I found interesting is that with certain components or platforms, less is sometimes more. Isodamp comes in a 12" x 54" sheet. Sometimes, four silver dollar size cut outs are all you need. Sometimes much more. Experimentation, as always, is key.
I use it as a constrained damping material, which means it is like the Oreo filling between two solid surfaces (rack shelf and component platform, for example).

I purchased mine through Rathbun in the Bay area of California. Friendly and helpful folks.

https://www.rathbun.com/e-a-r/damping-isolation#1

-Bruce

 

[213Cobra]

I strongly encourage anyone currently using Sorbothane in hifi resonance control applications to instead substitute one of the appropriate Grungebuster or dbNeutralizer products from Herbie's Audio Lab. I find these vastly superior to Sorbothane, which has many musical downsides with its upsides. The Herbie's materials are more unconditionally beneficial.
https://herbiesaudiolab.com/collect...products/damping-sheet?variant=12659631947831

Phil

 

[bazelio]

I'd go one step further and say Sorbathane has no place in an audio application. I've tried it as chassis footers, platform footers, chassis dampeners, and probably elsewhere over the years. Every time it has done more harm than good and usually a lot more. My feeling is that you have to be very careful about lowering the noise floor with any of these types of products. Because a long with the noise, you almost always end up evicting micro detail, blunting micro dynamics, and often sucking the life out of the music.

 

[Ron Resnick]

Hello 213Cobra and bazelio,

Do you feel that Sorbothane is bad even under a non-source component like a tube pre-amplifier, or like a tube amplifier in the line of fire of loudspeakers?

 

[bazelio]

Ron, I do, yes.

 

[tima]

Sorbothane can be effective in a constrained layer as WeatherB suggests. In another use, I had Mondo Designs amp stands that had a floating plinth inside a mape frame where the plinth sat on fat pucks of Sorbothane. The difference between the stands with and without Sorbothane was easily audible. With the pucks in place there was a general gain in focus and articulation. I disagree that it does more harm than good, but like everything else, application and implementation make a difference. Too much or used in the wrong way, then yes, just like any other damping material, it can deaden vivacity or detail. Does not make a good record mat. Sheets, pucks, half-spheres, etc. are relatively inexpensive.

What I don't like about Sorbothane is the fact that it wears out. Its efficacy diminishes over time which means gradually changing sound over time. Shelf-life (not under load) is around 2-3 years. Fatigue is a function of quantity, durometer, load and use. You may not be aware of gradual loss of effect ('creep') until you replace it. The warranty on any iso product using it is only as good as the sorbothane lifespan.

There are other proprietary visco-elastics used in audio iso and damping products that do not wear out, eg, in SRA products who formulates their own in-house.

 

[213Cobra]

Hello 213Cobra and bazelio,

Do you feel that Sorbothane is bad even under a non-source component like a tube pre-amplifier, or like a tube amplifier in the line of fire of loudspeakers?

I was initially being polite in encouraging an alternative to Sorbothane if an elastomer of some type is called for. I find it no good under any circumstances in hifi and much more often than not, its usage is deeply deleterious to musical fidelity. And yes, it will also suck life out of the dynamic vitality of non-source components placed on it.

Now, to people who say they've taken Sorbothane out of racks or other components where it was used, and they heard a difference, I say I am sure they did. Depending on how badly the structure or device was behaving with no resonance control, it might have even sounded better on first contrast comparison. But live with it and then judge. More to the point, if Sorbothane suggests elastomer-based resonance control would be desirable, take that as an indicator that there is *always* a better material to do that job. People get confused by the initial quieting effects of Sorbothane and don't take the time to identify everything it strips away.

A good place to start is Herbie's proprietary elastomers.

Another is that often it's not the soul-sucking dampening of Sorbothane that is needed but instead an energy-dissipating bearing.

My basic rule is "anything but Sorbothane." There's always something much better and net-positive. And as pointed out, it readily deteriorates as a rate you can't predict. You're the frog in a warming pot.

Phil

 

[ack]

I've written extensively about Isodamp in the past, it is truly sensational, and it has to be greatly compressed to be as effective as it can be. Its effect in increasing clarity dramatically has been most evident under the phono and speakers. Sorbothane is not good at all, has ugly resonances.

 

[ack]

and the effect of Isodamp can be easily verified with a stethoscope: I have it under my turntable motor, and there is slight whirring leakage to the base without it, gone with it. The effect of it when used throughout a system is transformational, because it effectively absorbs vibrations in wide range of frequencies. Contrast this with ringing metal shelves, plates, and other voodoo discussed around here.

 

[bazelio]

In my most recent encounter with Sorbothane, I placed Sorbothane hemispheres between a metal plate and my rack shelf, with an amplifier on top of the plate. Durometer was chosen so as to meet the total weight being supported. At first, I had the hemispheres "upside down" to minimize plate to Sorbothane contact area, knowing the propensity of Sorbothane to have majorly destructive effects on sound. When that didn't fail to cause major harm, I reversed and affixed them to the plate on their flat side. As suspected: even worse. And this isn't the first time I've encountered negative effects from Sorbothane even when indirectly coupled (i.e. not even directly touching any audio component).

So as those above have said: stay far, far away from Sorbothane. Directly, indirectly, constrained layer, all of the above. I won't even allow the stuff in the same room as audio gear at this point. I've finally learned my lesson. If @213Cobra decides to make "Anything But Sorbothane" T-shirts, I'll gladly wear one to the next audio show I attend.

 

[PeterA]

I once used Sorbothane pucks under an Equitech balanced transformer unit that did not have its own footers. This was placed on the floor near my equipment rack. The pucks left a stain on my wooden floorboards.

I then tried those Sorbothane pucks under the Equitech unit on the bottom shelf of my Zoethecus rack. Again the pucks left a stain on the finish of the rack's wooden frame members. I sold that rack long ago and apologized to the buyer about the stains.

I eventually sold that Equitech too preferring the sound of the system with a Transparent Audio distribution box instead. I now wonder if the problem with the Equitech was actually the Sorbothane pucks on which it was supported, LOL. Oh well, that was all a long time ago.

I did buy a collection of rubber footers from Mach One Audio in NH years ago. They look identical to the Isodamp black footers one can buy on the Rathbun website linked to above by WeatherB. I have no idea if they are the same or even similar. The guy from Mach One described them as developed by NASA or someplace as advanced vibration control. These things were amazing. They did not bounce when dropped to the floor, at all. Pretty impressive, until I placed four under a component. They surely did something dramatic. They attenuated, killed, "sucked out", or something, the complex harmonics. Notes were presented boldly in stark contrast and relief, but they sounded incomplete with little or no harmonic content. The music suffered, and so I threw them away shortly after I tried them and went back to the stock footers. Much better.

I think there are a lot of good and bad solutions out there. Everyone uses different shelves, racks, or supports, just like speakers, electronics, cables and sources. One must experiment, audition, and choose what works best for him in a given context and for his own taste. There seem to be some materials which work consistently better than others.

It seems so far that there is fairly strong agreement that Sorbothane is bad in all contexts for audio, and a few data points that multi layered birch plywood is problematic in shelf construction and large, solid turntable plinths.

Bazelio and I are getting good results with our steel plates after experimenting with different materials below them, some dampening them more than others. In my case, those stainless steel plates seem to be damped by directly sitting on the plywood shelves and don't sound nearly as good as when raised on rubber O rings. This seems to raise the resonant frequency when tapped by a finger or metal stick, but they don't ring per se, and certainly not perceptively when not agitated. I think it is about finding a balance and fine-tuning for the result one wants.

Some of us seem to be doing just that. I think this is a good discussion with lots of opinions.

 

[spiritofmusic]

and the effect of Isodamp can be easily verified with a stethoscope: I have it under my turntable motor, and there is slight whirring leakage to the base without it, gone with it. The effect of it when used throughout a system is transformational, because it effectively absorbs vibrations in wide range of frequencies. Contrast this with ringing metal shelves, plates, and other voodoo discussed around here.

Ack, could Isodamp be used in conjunction w mass loading to work as vibration sink on top of gear chassis', as per HRS Damping Plates?

 

[jackelsson]

Any experience with Sylomer anyone?

 

[ack]

Ack, could Isodamp be used in conjunction w mass loading to work as vibration sink on top of gear chassis', as per HRS Damping Plates?

It probably would, as long as the mass-loading device doesn't add a sound of its own (e.g. ring, etc). You just gave me a great idea! As I have said over the years, I started using Isodamp over a decade ago after reading about its applications in absorbing aircraft engine vibrations.

 

[Ron Resnick]

Ron, I do, yes.

Why, in theory, could that be? If a tube amp is sitting between the speakers on Sorbothane, what is the Sorbothane doing, possibly, other than converting vibration into heat before the vibration rattles the tubes, no? How can that not be unambiguously good?

 

[WeatherB]

Two points about isodamp:

1) It will leave a mark, similar I suppose to sorbothane. Something to consider before placing it on high value items.
2) I was told that isodamp "outgasses" water. However, I have had this stuff since November and have zero water problems.

Given the above issues, I am still using isodamp, just being careful what surface it is resting on.

 

[Ovenmitt]

Since I think I may be the original instigator here - Remdeck and Peter had asked some questions in my OP "Blond on blonde... On blonde" thread here: https://www.whatsbestforum.com/threads/blonde-on-blonde-on-blonde.30295/

From my experiences in building plinths, a constrained layer approach has worked best for me by far. When I first acquired a Garrard, I tried a stacked birch ply plinth. It was cheap, easy to build and it seemed to be what a lot of people were using at the time (Art Dudley are you out there?)... It worked okay and I loved the sound of this new turntable, in comparison to the VPI Aries I had at the time.

I am a guitar player and something made me start to wonder about using tone woods in a plinth - what works well for a musical instrument seems like it should also work for a plinth, right? I had been reading about the Shindo Garrard and also the plinths from ____ . My next plinth was made from two layers of 2-inch hard maple, with the grain running opposite in each layer - four inches total. If you happen to play guitar (or another instrument that uses maple - mandolin, violin, etc.) you'll know that maple is less warm, more linear, and has a "crisper", more extended top end; as apposed to something like Mahogany which is, generally speaking, warmer sounding. Long story short; the birch ply plinth ended up in the fire pit at a backyard party.

Since this, I have experimented with other tone woods - cherry, ebony, mahogany, and Engleman Spruce. They all sound different and I like them all for different reasons/applications. My experience suggests always using hardwood as apposed to softer woods like pine, soft maple, etc.

At some point I heard about Panzerholz and thought I would try that. I have since found that I really like using it as long as it's "layered" with other materials. In my Technics SP10 Mk.3 plinth I use it more extensively than in my Garrard plinths, because I want the Garrard to be a bit less damped. I also used a 1 inch plate of a aluminum in the SP10.

For the most part, I have built my plinths with a detached/seperate arm pod. I tried to make these arm pods as inert and damped as possible and they are almost 100% panzerholz on the inside. They are capped with either ebony or hard maple.

In my most recent plinth build I incorporated a layer of 2-inch bamboo - I was able to find a really large and thick bamboo cutting board on Amazon. I'm still tuning this 'table but so far I think the bamboo is a winner.

I have also started to experiment more with soapstone. It has some very interesting acoustic properties - much different than slate for instance.

Lot's more I can share and I will also try to post some pics later if anyone is interested.

 

[bazelio]

Why, in theory, could that be? If a tube amp is sitting between the speakers on Sorbothane, what is the Sorbothane doing, possibly, other than converting vibration into heat before the vibration rattles the tubes, no? How can that not be unambiguously good?

"In theory, there's no difference between practice and theory. In practice, there is." Your theoretical questions are what led me to Sorbothane quite a while ago. My ears are what have made me stay away from it entirely now. With my recent base plate experiment, I was once again curious, and not at all surprised by what unfolded.

Simple answer: I don't know. I don't know the resonance and isolation properties of Sorbothane. Perhaps this material is inefficient at transferring mechanical energy to heat. Perhaps it has resonant properties of its own that have a causal relationship with the results in audio systems. The dumbed down mental model I have of Sorbothane (to attempt to explain what I hear) is that it somehow resists energy transfer, possibly even reflecting or amplifying kinetic energy back into the component that it is supposedly isolating. Tubed components in particular will pick up environmental energy and all electronics have self-resonating properties. It seems that at some point, when we hinder energy transfer from a component (as my mental model of Sorbothane says), the worse our results become - muddy, smeared, blunted, etc. I think there is a balance to be found between absolute isolation and absolute coupling as well. The latter tending towards overly sharp, under damped, dry, analytical, etc. The right balance may differ from person to person, system to system. You'll know it when you find it, most likely. It does get tedious though... even on a rainy day during shelter-in-place edicts.