High-mass dampening vs. Low-mass draining: I'm confused ...

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6BQ5

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These two concepts have always confused me. Perhaps they are the same? I'm not sure anymore.

I'm thinking specifically of turntables.

You have the Rega designs which try to minimize mass to quickly and efficiently "drain" away vibrations and resonances.

And then you have high-mass designs, for example, slate plinths people are using for for old Garrards, Thorens and Lenco which seem to be built to absorb it all.

Which is the "right" approach? I read places where people over-damp and kill the sound. Other times, it seems dampening exacerbates resonances.

For example, putting a Herbie Damper on a tonearm, seems to me kind of risky. Isn't the tonearm in itself designed to deal with micro-vibrations ... won't you be removing some important information potentially in trying to absorb them at some critical point?

I read places where people say brass is great for feet under a turntable because it is effective in "draining" vibrations and one should never use delrin, visco-elastic or synthetic materials such as sorbothane which supposedly make the sound muddy. But people seem to be using both out there. Sheesh ... my head is spinning with all the different points of view.

Please help.

Herbie

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Re: High-mass dampening vs. Low-mass draining: I'm confused ...
« Reply #1 on: 30 Oct 2009, 10:10 pm »
The two concepts are neither the same nor mutually exclusive. Neither is inherently "right" at the exclusion of the other. They both work toward the same goal: to reduce microvibrations that affect sensitive electronics and distort the music. Both concepts can be engineered into equally effective products. (Turntables are also particularly susceptible to macro-vibrations, such as footfall on a suspended floor; neither high-mass damping nor draining alone will alleviate these vibrations.)
 
High-mass materials don't necessarily absorb microvibrations due simply to being high-mass. Mass and density help to control vibrations as much by confining vibrations as by absorbing them. Generally, the harder a material is, the more readily it will transmit vibrations instead of absorbing them. This lends these materials to attempts to "drain" vibrations away.
 
Unfortunately, draining vibrations doesn't always work as well in practice as in theory. There is no "traffic cop" to direct vibrations to the drain. Microvibrations are more like ants at a picnic, traveling in every which direction, especially through and between hard materials. Some vibrations are drained, but to where? To the rack, where they will reciprocate back to the component re-armed with sonic character from the rack and infiltrate other components. Or to the floor, where they will reciprocate back into the rack and across to the speakers. Hard materials, brass, even the hardest metals and ceramics, virtually all have unique sonic signatures that they introduce into the vibrational environment. Rigidly coupled systems, whether high-mass or low-mass, usually have a lot of detail, but tend to be harsh. To reduce coloration and bring out more ambient detail, it's usually best to have some compliance to break up the flow of microvibrations through rigid materials.
 
Softer materials can absorb and block micro and macro-vibrations. Most compliant materials like rubber and Sorbothane, however, have resonances that cause bloopy bass and muddy sound. It's a trade-off: some vibrations are reduced while others are introduced. Materials with very low resonant frequencies are usually too "slow" to provide the counter-vibrational response necessary to absorb acute higher frequency vibrations that cause so much glare and harshness. To best achieve the kind of vibration control necessary for audio equipment, you need materials that are formulated specifically for the vibrational environments that are peculiar to audio systems.
 
It's usually not possible to "overdamp" strictly by reducing vibrations. When the damping material itself has any sonic or resonant character, though, or when it simply alters the vibrational environment, overdamping happens readily. "Overdamping" also occurs when symbiotic relationships between parts are altered. For example, let's say microvibrations cause a CD player to emphasize higher frequencies and this is "corrected" by attenuating higher frequencies at the speakers. If the vibrations that cause the emphasis in the first place are then reduced, allowing the CD player to provide a true and linear result, the attenuation at the loudspeakers would then overcompensate, resulting in what might be perceived as "overdamping" of the CD player.
 
If done properly, damping a tonearm is beneficial because it reduces unwanted vibration. The tonearm does not carry information by vibrating. A tonearm functions best when holding the cartridge as vibration-free as possible, allowing the stylus to accurately trace the record groove and vibrate only according to the information cut into the vinyl--not by intrusive vibrations. (When damping a tonearm, you'll adjust the counter-weight so the stylus pressure and arm pivot keep the same sensitivity.)
 
With damping and isolation in general there is no "right" or "wrong" approach. You need both. Some parts you want rigid and/or dense; with others, you want some compliance and "give."
 
For more insight into related topics, there is a thread further down on this Circle called, "coupling vs. isolation" and an overview of Herbie's compliant footers here:
 
Footers FAQ
 
Best regards,

Steve Herbelin
Herbie's Audio Lab
« Last Edit: 23 Aug 2010, 01:30 am by Herbie »

6BQ5

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Re: High-mass dampening vs. Low-mass draining: I'm confused ...
« Reply #2 on: 31 Oct 2009, 01:35 am »
Thanks for the education Steve.

What are the best places to focus on (and avoid) with a turntable?

Feet and platter obviously ...

How's about other places such as headshell, tonearm, healdshell to tonearm mounting point, within the plinth, cables, etc...

Herbie

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Re: High-mass dampening vs. Low-mass draining: I'm confused ...
« Reply #3 on: 31 Oct 2009, 02:05 am »
Yeah, I think you got the idea. To start, the mat, especially if it's felt or rubber. Footers are worth considering, as is shelf/rack or platform integrity, and motor mount.

Herbie's Audio Lab has customers who have addressed all of the other areas you mentioned. Herbie's grungebuster material (sheet and dots) tend to work particularly well with turntables and is often used for headshell, tonearm mount, and plinth interfaces. Rope caulk (available at hardware stores) can be used to damp underneath semi-hollow cast-aluminum platters that are sometimes prone to ringing. Permatex Blue RTV Silicone Gasket Maker is great for damping electronic mounts, wiring and connections.

I can't think of any particular places to avoid, except to proceed conservatively. You might google your particular turntable model to find out what others have done.

Steve
Herbie's Audio Lab
« Last Edit: 23 Aug 2010, 01:30 am by Herbie »

6BQ5

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Re: High-mass dampening vs. Low-mass draining: I'm confused ...
« Reply #4 on: 31 Oct 2009, 02:15 am »
1) Why are felt and rubber bad?

(I know, like saturated fats they are probably not good for me) .... but why?
Felt seems to dampen. Linn believes that felt is the best material for their LP12 tt mat (for some reason).

2) What are some of the better materials to use?

For example with platters, I see a variety of materials people recommend: acrylic, magnesium, high-grade (aircraft) aluminum, ceramic oxide (Rega), damped carbon, air-injected vinyl, CU-180 copper, brass, CLD steel ...  even pig buckskin ... there seem to be so many people claiming that their material is better.

There must be some kind of rules to go by.
 

Herbie

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Re: High-mass dampening vs. Low-mass draining: I'm confused ...
« Reply #5 on: 31 Oct 2009, 02:45 am »
Felt and rubber are not bad. But you can do better.

Felt does not damp vibrations much. It is a relatively effective decoupling interface though, because it provides somewhat of a vibration barrier between the record and platter. One of the most common complaints about felt is that it retains too much static electricity on the vinyl.

Though the LP12 does very well with a felt mat, hundreds of LP12 owners use a Way Excellent or Way Excellent II Turntable Mat for even better results. Look over the reviews on our website; you'll see many enthusiastic comments/reviews from LP12 owners--likewise with Rega owners and others who have upgraded from the standard felt mat:

Reviews/Comments

Rubber mats have resonance issues that tend to blur some of the finer inner detail and tonal textures of music and sometimes rob the bass of true linearity and extension. The open-cell silicone foam used with the Way Excellent II mat is much more efficient at damping vibrations and provides a more revealing, faithful, and linear result. Most importantly, it makes the music sound better.
 
I suppose there are fewer materials suitable for a mat than for a platter, because with a mat you are decoupling from the platter and in intimate contact with the record itself.
 
Vinyl and carbon mats have been known to provide good results, but tend to be somewhat picky about what kind of platter they are associated with. (In my estimation, shelf-liner, cork, and Sorbothane are not amongst the better materials.)
 
Best regards,
 
Steve
Herbie's Audio Lab
« Last Edit: 23 Aug 2010, 01:31 am by Herbie »