Damping Vibration - Friend or Foe?



Hi All,

I have been reading many discussions regarding the use of damping in and around audio components here on Audiogon. I thought that the following discussion from the FAQ page of my company’s website would add a little clarity. The example here involves a home theater system but the same principles hold true for an audio only system.

Question: Some people claim that adding damping to components to control vibration can sometimes make them sound less dynamic and somewhat lifeless. Why should this be so when damping reduces the problems of vibration and resonance?

Answer: I have also heard the same comments a number of times. Unfortunately, people mistakenly attribute these negative changes in performance solely to the addition of damping to a component. If we look at the entire evolution of an audio or video system we can gain a much more clear understanding of what is happening and why it is happening.

Let’s say that John, who is an audio and video enthusiast, decides to put together a really nice home theater system. He reads a number of magazines, visits websites devoted to these topics and assembles a system composed of many highly rated components. John sits down to enjoy a well produced action movie but a few minutes into the first scene realizes that he’s not hearing or seeing what’s been described in the magazines by the reviewers. The highs are bright and harsh, the midrange is forward and the bass is bloated and ill defined. The video picture is also disappointing – the images are not very sharp or detailed, it looks rather two dimensional and the color is only so-so. What’s going on? These are all really good and pretty expensive components!

John decides to try different interconnect and speaker cables to deal with the audio problems. After two or three weeks of trying a number of different brands he decides on Brand X between the converter and the surround processor (it had the smoothest highs) Brand Y between the processor and the amplifiers (it had the best midrange) and Brand Z to the subwoofer (it had much better bass). In addition, he spent a many hours trying different speaker positions. It also happened that the cable between the DVD player and the video projector John chose was from Brand X - it reduced many of the video problems he was seeing. He then had a technician come out and recalibrate the projector for this new cable. Now John is happier with the system, after all, he even switched the front amp for a different brand. But after a few weeks he is still noticing that the highs have sibilance during loud passages, are still kind of bright, and the midrange, although better than before, still honks a little and is not that distinct on complex dialog. Plus imaging is good but not great. The bass is better but he’s had to try the subwoofer in nine or ten different positions and, of course, the one that sounded best was right in the middle of the walkway!

John is bummed but starts thinking about acoustical treatment for his room and decides that adding some of that will surely make the system sound great. He borrows a bunch of different devices from a number of dealers and spends all day and night Saturday and Sunday trying all of the devices in different combinations and positions. By 11:59 P.M. on Sunday night he’s finally found the best compromise that takes care of many of the other audio problems, although some still remain.

All this work has left John exhausted but happy for a couple of months. He can now at least enjoy watching movies but increasingly is annoyed by the remaining audio and video problems. Over time he’s also noticed some new problems he hadn’t noticed before!

Well, now what? John does more reading. He’s read about vibration control before but now starts to think more seriously about it. He knows that Brand B’s products (high-mass and high-absorption damping devices) get great reviews and have won lots of awards so he decides to try them. He places a compliant decoupling platform on the shelf, a high-mass and high-absorption isolation platform on top of the compliant platform, the DVD player on top of the high-mass platform and a high-mass damping pod on top of the DVD player and the surround processor. Well just about all of the remaining audio and video problems are now gone – the highs are very smooth, the midrange is clear and the bass is much tighter, the video picture is far better – but somehow things sound constricted and lifeless. John likes the improvements but is not very sure that this is good thing overall.

What is really going on? As we’ve seen, John has taken a fairly convoluted road to reach the point of trying the damping products. Along the way he has made many choices of associated components, accessories and set-up to optimize the system. “Optimize“ has mostly meant reducing obvious and subtle problems and enhancing certain other aspects of performance. Unfortunately, much of this effort has been an attempt to reduce the negative audio and video artifacts of vibration contamination. The choice of cables, acoustic treatment devices, speaker position, etc. have all been made to ameliorate the SYMPTOMS, not the CAUSE of the problem – vibration! Once the cause of the problem is eliminated, the system shows itself for what it is – a system where the highs and mids have been pushed down in level and dynamic range because of acoustical treatment devices and associated components, where imaging has been manipulated by speaker position and acoustic treatment to compensate for random out-of-phase elements, where subwoofer position has been chosen as a compromise, where video calibration and associated components have been selected to compensate for vibration induced jitter and other artifacts in the video bitstream, etc., etc., etc. It is no wonder that John was under-whelmed when he added the damping devices!!

Also at issue is the fact that the designers of the components in the system have voiced their designs with vibration (most probably) present in their reference systems. They have compensated for the problems introduced by vibration and resonance by changing parts and topology to minimize the symptoms (not the cause) of that problem. It is quite possible that effectively eliminating vibration and resonance with damping is letting you REALLY hear how the component has been designed.

It is often the case that the choice of set-up, associated components, ancillary accessories, acoustic treatment, etc. has to be significantly and fundamentally reevaluated when adding devices that eliminate basic problems in a system – especially problems that are as pervasive and permeating as those brought about by unwanted vibration and resonance.

Best Regards,

Barry Kohan

Disclaimer: I am a manufacturer of vibration control products.
bright_star_audio
Hi Peacefrog,

Thank you for your question.

I would expect that we all agree that vibration alters the signal and that has an audible effect on the performance of a component. If we are attempting to reproduce the information that is contained in the recording as accurately as possible, any fundamental problems which affect the system which is processing the recording's information should be addressed at the outset (most audiophiles seem to address them after the fact).

The three most important problem areas are:

1) Vibration Control - My views on vibration control are well explained on my website (I can restate them here if you wish). Eliminating all vestiges of vibration contamination will ensure that the fragile frequency / amplitude / phase relationship that is contained in the recording remains undisturbed.

2) AC line quality - The AC lines should have as much current as possible delivered to the outlets, the grounding should be as stable as possible, the AC energy itself should be as clean and ripple free as possible and all constituant parts (wire, outlets, breakers, etc.) should be as high quality as possible.

3) Room Acoustics - A room's acoustic should provide absorptive/reflective surfaces as uniform as possible over the entire frequency and amplitude range. This will ensure that the fragile frequency / amplitude / phase relationship of the wavelaunch that eminates from the speakers remains undisturbed.

Once these fundamental areas are addressed, you can then really make accurate value judgements on the performance of the components which comprise the system.

Best,

Barry Kohan

Disclaimer: I am a manufacturer of vibration control products.
Thanks for the response Barry. I've just recently become interested in vibration and power issues because I just moved into a 75-year-old house, and the system is in a second floor room with hard wood floors. I know the floor vibrates easily and that this vibration is being transmitted to my gear. Question is, will I be able to hear a difference given the mid-fi gear that I have? I also expect that I have some power issues since the wiring is also 75 years old and is ungrounded. I would love to upgrade the wiring, but it's just not feasible right now. But an inexpensive power conditioner is do-able. Again, is it worth the bother?
Barry, I wholeheartedly agree that vibration handling, electrical, and room acoustics are, in and of themselves, all very critical areas that should be proactively addressed individually. As properly addressing these items can translate to a real improvement in one's musical experience.

However, in your post above, you made the following statement:

"Eliminating all vestiges of vibration
contamination will ensure that the fragile
frequency / amplitude / phase relationship
that is contained in the recording remains
undisturbed."

This is difficult for me to comprehend because it is my understanding that it is simply impossible for vibrations and resonance to not disturb the components, rack, and speakers unless these items were placed one or two rooms away from the listening room.

My own little home-grown analogy for lack of one's ability to eliminate vibration via dampening and/or isolation is the following:

"You're in your vehicle at a stoplight. Somebody three cars behind you pulls up with his subwoofer blasting. You feel the beat in your sternum and gut. You look in your rearview mirror to catch a glimpse of the guy 3 cars back and your rearview mirror is really vibrating."

But the question is, Why? If the other guy's car is sitting on rubber air-filled radial tires and yours is too, and you are sitting on a well-cushioned seats and your rubber-surround windows are rolled up, why are you not completed isolated from these vibrations? Why not your rearview mirror? Now imagine how much worse that guy's chest and rearview mirror are vibrating.

Should not these air-filled radial tires and the space distance between the vehicles be deemed an excellent means of dampening and isolating vibrations?

Using that analogy and it's real effects as an example, I would conclude that it is simply impossible to 'eliminate all vestiges of vibration contamination' as you put it.

That, and the results of my limited experiments, are why I believe it is best to expedite the transfer of these nasties away from the components, rack, and speakers via the coupling methodology.

That is in contrast to simply de-couple and hence trap those vibrations inside each component and thus potentially reeking havoc on the innards and subsequent sonics.

Please correct me if I am wrong.

-IMO
Peacefrog is this your 75 year old house? If it is then spend your money on a properly installed dedicated ac line using 10 ga.copper with isolated grounds and quality ac outlets..A power conditioner may be in your case like putting a band-aid on a severed hand..It all comes from the power company thru their line and to your hi-fi on YOUR LINE..2 to 3 hundred dollars should take care of the line..At my home on my system I found all power conditioning to be a negative----not a positive+++Tom..Ps direct coupling sounds the best to me..I side with Stehno. Dampening kills the music..