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Impact of vibrations?  

post #1 of 57
Thread Starter 

Yesterday I have attended a presentation where a high end CD player was standing on a normal table, and then moved to a special rack. With no other changes (and the remaining components including amplifier staying in the same location), this has affected the sound rendition. I'm not going to go into whether it was better or worse - the point is that as far as I can tell all the attendees (100+) have noticed a difference. 

 

Normally I'm not susceptible to placebo effects and my initial attitude was extremely skeptical, but I have heard a difference. Is there a scientific explanation of this phenomenon? 

 

The presenter explained that the rack construction deploys several technologies to minimize vibrations, standing waves etc. Could that have any audible impact?

post #2 of 57
Quote:
Originally Posted by PleasantSounds View Post

 

Normally I'm not susceptible to placebo effects and my initial attitude was extremely skeptical, but I have heard a difference. Is there a scientific explanation of this phenomenon? 

 

Vibrations themselves, it effects everything from macro to nano materials, has to do with a material naturally having thermal energy(talking only for small materials) at room temperature

 


Quote:
Originally Posted by PleasantSounds View Post

The presenter explained that the rack construction deploys several technologies to minimize vibrations, standing waves etc. Could that have any audible impact?

 

my guess would be less skips when reading off of the CD, I think the stylus(not sure what the correct term is with cd players but this what I will call it for now) should be small enough such that vibrations will effect its mechanical work causing misreads, pretty impressive if you can hear the misreads but if it the CD player is high-end enough, it should've taken care of this mechanical issue by itself and not need a rack to help it

post #3 of 57

Why did he use a CD player? A CD player can be affected by vibrations because it is a mechanical playback system. The same with a turntable. Mostly to control the resonant frequency.

post #4 of 57

If you need a high-end CD player and a special rack to read the correct bits off of a CD (or rather, the correct bits come out of the Reed-Solomon error-correcting decoder—many errors in terms of individual 0s and 1s as interpreted by the laser reading mechanism, can be tolerated, where you end up with the original data 100% accurate), then everybody's software they installed of a CD must be corrupted because they read the wrong data off of the disc...

 

Or, if the CD player is not just a transport but did the D/A, the DAC was affected by being on a rack?  Must be some kind of DAC.


Edited by mikeaj - 2/20/13 at 6:37pm
post #5 of 57

CD players work perfectly fine in a moving car. You don't need some special rack to prevent vibrations when it's just sitting there.

 

If the bits are all scrambled from vibrations than it would be extremely noticeable, not some change in sound signature, clarity, etc...

post #6 of 57

I am curious about what the difference is. Not too long ago, people actually exercise with a CD Walkman. The first generation used a small buffer and compression to fit the bits into the buffers. It was reported then, a large buffer with no compression sounds better. I wondered if this actually an effect of the DAC buffer?

 

Any other errors read by the CD player are typically characterized by pop and click noise. So I don't really believe any reading enhancement on the part of the CD player.

post #7 of 57

I just read this on the diyaudio forum, not sure if its correct.

 

Some say that the capacitors are microphonic.

Some are saying the clock will be affected by these vibrations (crystal oscillators are susceptible to vibration http://www.maximintegrated.com/app-notes/index.mvp/id/2154), others say its due to the tracking issues.

post #8 of 57
Quote:
Originally Posted by PleasantSounds View Post

Yesterday I have attended a presentation where a high end CD player was standing on a normal table, and then moved to a special rack. With no other changes (and the remaining components including amplifier staying in the same location), this has affected the sound rendition. I'm not going to go into whether it was better or worse - the point is that as far as I can tell all the attendees (100+) have noticed a difference. 

 

Normally I'm not susceptible to placebo effects and my initial attitude was extremely skeptical, but I have heard a difference. Is there a scientific explanation of this phenomenon? 

 

The presenter explained that the rack construction deploys several technologies to minimize vibrations, standing waves etc. Could that have any audible impact?

How was the rack constructed? What materials? Manufacturer making the claims?  CD player brand/model?  

 

Sorry, some details would help evaluate this.

post #9 of 57
Quote:
Originally Posted by proton007 View Post

I just read this on the diyaudio forum, not sure if its correct.

 

Some say that the capacitors are microphonic.

Some are saying the clock will be affected by these vibrations (crystal oscillators are susceptible to vibration http://www.maximintegrated.com/app-notes/index.mvp/id/2154), others say its due to the tracking issues.

Some capacitor types are more microphonic than others, some types display almost no microphonics.  It gets down to picking the right parts.  

post #10 of 57
Thread Starter 
Quote:
Originally Posted by jaddie View Post

How was the rack constructed? What materials? Manufacturer making the claims?  CD player brand/model?  

 

Sorry, some details would help evaluate this.

 

If I remember correctly, the rack was the Quadraspire Sunoko Vent T: non-rectangular shelves with wood finish but most likely MDF based, solid aluminum columns, spiked feet.

The CD player was the CD5 by Audio Research, connected to AR DSi200 and playing through Cremona M speakers. The CD5 DAC has been used (xlr connection to the amp).

 

Regarding the impact I have heard, I could describe it as sounding somewhat veiled and less engaging in comparison, when based on "normal" table. The base has been swapped several times back and forth and the impression was consistently the same, with several music samples.

post #11 of 57

Very often differences are ascribed to the obvious change.  But it could have been caused by interference or a ground loop or a defective cable or a bad connection or something.

 

Now many of us have the necessary equipment to investigate possible vibration problems.  Place the test component on a sub-woofer that is playing loud bass heavy music.  Using another music source feed the test component more refined music and silent periods,  then record the output of the test unit.  You will have to take some care adjusting the volume of all the steps in the test chain to get realistic results.


Edited by Speedskater - 2/21/13 at 6:02am
post #12 of 57
Quote:
Originally Posted by PleasantSounds View Post

 

If I remember correctly, the rack was the Quadraspire Sunoko Vent T: non-rectangular shelves with wood finish but most likely MDF based, solid aluminum columns, spiked feet.

The CD player was the CD5 by Audio Research, connected to AR DSi200 and playing through Cremona M speakers. The CD5 DAC has been used (xlr connection to the amp).

 

Regarding the impact I have heard, I could describe it as sounding somewhat veiled and less engaging in comparison, when based on "normal" table. The base has been swapped several times back and forth and the impression was consistently the same, with several music samples.

Thanks for the details.  I looked at the Quadraspire site and saw their shelving system.  

 

What I was looking for was some way in which their rack would create a mechanical low pass filter tuned for cut-off below the audio band.  This can be done by adding mass and placing a resilient decoupling mechanism between it and the source of vibration.  When I look at the rack I don't see any resilient decoupling or added mass.  I see they've increased the tension in the joints and placed spiked feet on the legs, both of which would actually increase vibration coupling to the floor. The MDF material is not reinforced, which I would have expected in order to tune the diaphragm each shelf creates to a higher frequency.  And of course the entire thing is open to air, so any airborne  vibration coupling to components is unaffected.  

 

To isolate something from the vibration generated by a sound system the method of vibration coupling has to be determined.  In this case, there are two paths.  One is through the air itself, and the other is coupling from the floor, which carries vibration physically coupled from the speakers as well as vibration the floor itself picks up, acting as a diaphragm, from the air.  The floor is physically coupled to components from table or rack legs and supports and then the shelves.  So a more isolated rack would be an air-tight box made of several layers of massive material, each layer isolated from the other through resilient couplings adjusted so that the mass of the innermost rack and the couplings create a mechanical high pass filter tuned well below audio frequencies.  The air tight box would effectively prevent air coupling, and the isolation system would reduce floor coupling.  Considering all of that, it would make more sense to put the components in another room and work on resilient mounts to decouple a standard rack from the floor. The results of all of this are easily measured and confirmed with an accelerometer placed on each component in various locations.

 

Physically moving a component within a room completely changes the coupled vibrations, and not to a small extent.  Bass modal distribution, especially without multiple bass transducers, can be very spotty, and just moving away from the mid-band sound source can reduce the airborne vibration by several dB.  You don't have to change the rack to achieve that.  

 

I'm not certain what you heard, but I'm pretty sure it wasn't because the rack was changed.

post #13 of 57

Maybe I'm too indoctrinated in the generally sceptical attitudes in SC, but I think jaddie's extremely thoughtful reply (as usual) is too kind.

 

If the presentation was set up to increase sales of this rack, I say it's BS. It sounds like it was even a sighted (i.e. non blind) test! No doubt with cues and suggestions from the presenter to increase your expectations, as well as the scientific terms you already mentioned to impress/confuse.

 

It's a cheap looking rack with a huge price tag. The most likely explanation is that you were tricked into hearing a difference to make a sale.

post #14 of 57

That may be the first time I've ever been accused of being '"too kind"! 

 

And my mean knob even goes to 11. 

 

I don't usually attack people for marketing.  In fact, based on my own less than successful attempts, I'm filled with respect and awe if it works at all, regardless if based on a fallacious foundation. Bose...OMG! Nice work!

 

Doesn't stop me from pointing out the fallacy though. 

post #15 of 57
Thread Starter 

Thanks for all the comments. I remain puzzled as my brain does not accept what my ears have heard. I can't eliminate the possibility that the presentation was somehow rigged, nor that it was a placebo effect. Just trying to find a plausible theory supporting this experience. 

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