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 Albert,

My impression from some of the responses I received to my thread "Can Manufacturers Post and Reply?" was that manufacturers should operate under more stringent guidelines than "civilian" Audiogon members. Do you think I'm maybe being a little too cautious?

Best,

Barry
Barry: Forget what i said earlier i.e. i'll keep my big mouth shut. You've obviously been asked a legit question by someone that wants an answer. Have at it. Sean
>
Hello Psychicanimal,

Quadruple de-ionization is a term that Garth Leerer, my main distributor and wordsmith came up with to define 4 cycles through dual bed DI tanks.

If you'd like to discuss this further, feel free to e-mail me directly so that we don't distract from the original thread topic.

Kind regards,
Brian Weitzel
Record Research Labs
recres@msn.com
Hi Albert,

Bright Star and Gilmore Audio shared three display rooms at CES and T.H.E. show in January. I had been familiar with the design for a number of months before CES and had seen one of the raw panels but had not heard the speakers before set up day.

I have been designing, building and modifying speaker systems since I was sixteen years old (I’m now forty seven) and have extensive experience with ribbons, planer-magnetic speakers, electrostatics, hybrids, dynamic speakers, line source and dipole designs. I have designed speakers professionally for over twenty years.

The presentation of Abraham Laboriel’s 5 string Yamaha bass through the Gilmore speakers at CES was exceptionally clean, well controlled, had outstanding dynamic range and I would say had the best articulation I have ever heard from a live electric bass guitar.* (I have been a professional musician – drummer – since I was sixteen years old and have heard many electric bass guitars through many different amplifiers and sound reinforcement systems. I have also played extensively in totally acoustic music ensembles and have been exposed to the sound of live, unamplified instruments in many different situations). I was present for at least ten of Abraham’s performances during the show. The subtlety and definition of each note that Abraham played was very well exhibited by the Gilmore speakers. Abraham has such amazing bass playing ability that even his 32nd notes (!) were each individually identifiable. That is a testament to his virtuosity and the speaker’s resolving power.

I have read a few posts on Audiogon and in few other sources from people who thought that the Gilmore’s bass response was not as extended as the manufacturer claims (the Model 2 Gilmore speakers are spec’d to 17 Hz) . Most of them seem to have based their comments on only a five minute session listening to Abraham playing his Yamaha bass live through the speakers. Unfortunately, this limited exposure is not representative of the speaker’s true capabilities. Abraham’s five string electric bass only extends down to slightly above 30 Hz. The instrument itself does not go lower. Unfortunately, many listeners are only exposed to live bass sound that is highly non-linear due to gross resonances in bass guitar amplifier/speaker setups, poor sound reinforcement systems and generally deaf sound engineers. Additionally, listeners who are used to bass reproduced through the vast majority of home systems have gotten accustomed to bloated bass from speakers that are not well designed and which exhibit resonances, overhang and poor integration with the room and its boundaries. The Gilmores did seem to go down quite low when a CD or LP was played through them.

The midbass, which is usually the Achilles’ heel of planer/dynamic hybrids was handled very well by both the Model 2 and Model 3 Gilmores. I did not hear obvious discontinuities or upper pass band response from the woofers that was out of proportion at the crossover point to the ribbon.

Transparency from the Gilmore speakers was also quite good and they lacked the glare and the intermodulation artifacts that plague the vast majority of planer speakers (and most dynamic speakers). I seem to be more sensitive to IM problems than many audiophiles and sound engineers. Midrange response was also quite good without exhibiting the etching and upper midrange brightness that most people describe as “detail”. The top end was also transparent and free of exaggerated brightness. Most speakers have high frequency response that is brighter than the musical instrument it is attempting to reproduce would be if both were played side by side.

Any areas of performance that were not exceptional could have been attributed to a number of conditions that are typical of show set ups: room acoustics, atmospheric conditions (dry air, over-heated rooms, too many human bodies in a small space, etc), sagging AC lines, the perennial problem of equipment that is not fully broken in before the show begins, etc. Demo material (particular recordings) used can also make a HUGE difference in people’s impressions of a show system. In addition, even though the relatively normally powered Atma-Sphere amps that were used to drive the speakers at CES did a valiant job and reached pretty good volume levels, I look forward to hearing the Gilmores with those intense MA-3 mono blocks or another mega amp that matches the speaker well. I am a firm believer in “over kill”.

My statements above are not meant to give the impression that I think the Gilmores are perfect (or any other speaker is perfect for that matter) and that there isn’t room for any potential improvement. I would have to spend much more time with them under controlled conditions to assess their ultimate capabilities. I would also like to run a number of measurements of their performance before I could make that determination.

Best,

Barry Kohan

* Abraham's playing was a mezmerizing experience. Every time I heard him play I was blown away with his virtuosity and said to myself that he couldn't possibly play any better, but amazingly enough he DID play even better the next time!