Head-Fi.org › Forums › Equipment Forums › Sound Science › Impact of vibrations?
New Posts  All Forums:Forum Nav:

Impact of vibrations? - Page 2  

post #16 of 57
Quote:
Originally Posted by PleasantSounds View Post

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. 


You don't need a rack to control vibrations - the rack's mostly for aesthetics. I've done well with just books n top of my ancient CDP, but later I got a bit of marble tile and glued a rubber sheet on one side. Same effect, more compact. With car audio CDPs the problem despite their working fine there is there's no way to test it on a rack in a moving car, but of course that would slide off, so basically assume that the mounting of the CDP chassis onto the dashboard plus some additional hardware inside between the chassis and transport helps. Plus the smaller surface area of the chassis of a car CDP vs all that space on a home audio player that can get all those vibrations.

 

Two things I did to eliminate their impact : first, I used headphones. I couldn't tell any difference with the same CDP whether it was loaded with weight or not. Second, I went solid-state (iPad+CCK) unintentionally when I got one as a gift, but no matter how effective that is in theory in all honesty I can't hear any difference between my laptop with a platter HDD vs the tablet (I can't really compare them to the CDP though since I was using them via USB), but then again, the HDD has a buffer.

 

In related news, I've seen worse voodoo from some audiopiles - like that guy on YouTube who wrapped all his gear in ERS Paper, but then he has his amp and preamp on a Spider Rack while his Cary CDP or transport was on his Ikea table.

post #17 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.

 

That must have been a pretty funky CD player, because I have an old Diskman that you can turn upside down while it's playing and not have any problems.

post #18 of 57

I have had bad experiances on CDs that arent clean enough etc...

and weird angles of CD players that didnt at the time have anything to help hold CDs in place, back in the days where flying saucers were a serious risk to human health, I am not being facetious.

 

Most vibrations should not impact CD players enough to require dampening technologies.

post #19 of 57
Quote:
Originally Posted by ProtegeManiac View Post


You don't need a rack to control vibrations - the rack's mostly for aesthetics. I've done well with just books n top of my ancient CDP, but later I got a bit of marble tile and glued a rubber sheet on one side. Same effect, more compact. 

Adding mass on the top of a device's cabinet won't do much to isolate the mechanism or electronics from vibration because of the way vibration is transmitted.  There are two paths, one is by physical contact with a portion of structure that is vibrating, and the other is airborne vibration.  

 

Here's why adding mass on the top cabinet doesn't work:  If the vibration is airborne, it's passing through the cabinet, shaking it along the way, and then shaking what's inside.  If you mass-load the top of the cabinet, you've only addressed one surface, there are 5 others, some of which probably have ventilation holes which let heat out and sound in.  Then, for mass-loading to reduce vibration it has to create a physical low-pass filter tuned below the offending frequency band. The two components of that filter are the mass itself and a resilient coupling between the mass/device and the source of physical vibration.  The resilient element is analogous to an inductor in an electrical low pass filter, and the mass is the capacitor.  If you don't have the inductor, or it is very small, you won't have a significant low pass filter, so the resilient element is essential, and little felt or rubber pieces under the feet won't tune the cutoff frequency significantly. 

 

Then there's the sound in air penetrating the cabinet and shaking the inner parts.  Adding mass to one surface may reduce its diaphragmatic vibration, but leaves others to remain just as permeable as always.  Some surfaces of the cabinet will probably be vented, so they are transparent to sound.  So adding mass has no effect on the airborne vibration.

 

To reduce vibration from a device both the airborne path and the physical path have to be reduced, decoupled, or filtered.  Dealing with the physical path is easier, just add resilient mounts under the device then mass-load it so the mounts compress into the center of their operating range.  Under-loading or over-loading resilient mounts makes them far less effective, sometimes completely ineffective.  It might take quite a bit of mass and resiliency to tune the physical filter down below the audio band, though.  

 

Airborne isolation is more difficult. It basically takes a sound isolation room, even if it's fairly small for gear only.  Double or triple walls, air locks, suspended tops, bottoms, and sides, and the hard part...air tight.  Air tight also means heat tight, and that's where this gets complicated.  You need to get heat out without opening an airway to a sound leak so a sort of muffler system is required.  All in all, it's easier to move the gear to another room and improve both airborne and physical vibration isolation.  

 

Anyway, you'll get the idea that trying to isolate components from vibration isn't as simple as adding a brick to the top, or mounting the thing on a magic shelf.

 

Edit: corrected "resistor" to "inductor"


Edited by jaddie - 2/23/13 at 10:31am
post #20 of 57

Why do we need to do all this? I forgot.

post #21 of 57
Quote:
Originally Posted by bigshot View Post

Why do we need to do all this? I forgot.
We don't. The point is, shelving, racks, and weights have nearly zero impact on internal vibrations excited by external sources. To achieve real isolation is very involved. The other issue that I didn't address is if devices are sensitive to vibrations and what impact that may have audibly. As you can see, the ineffective nature of the solution might indicate something about the problem.
post #22 of 57

Ah... OK. It started getting so complicated, I began to think it was important.

post #23 of 57
Quote:
Originally Posted by jake120 View Post

I have had bad experiances on CDs that arent clean enough etc...

and weird angles of CD players that didnt at the time have anything to help hold CDs in place, back in the days where flying saucers were a serious risk to human health, I am not being facetious.

 

Most vibrations should not impact CD players enough to require dampening technologies.

 


I find it prudent to spray some water on my CD player before loading in the disc too.

post #24 of 57

10W40 oil works even better.  Smoother sound.

post #25 of 57
Quote:
Originally Posted by jaddie View Post

10W40 oil works even better.  Smoother sound.

It might be "better" if you like a colored sound, but if you're shooting for transparency water is the clear winner.

post #26 of 57
Quote:
Originally Posted by chewy4 View Post

It might be "better" if you like a colored sound, but if you're shooting for transparency water is the clear winner.

 

biggrin.gif but also note that water still causes distortions by means of refraction. therefore compressed air is the best.

post #27 of 57
Quote:
Originally Posted by PleasantSounds View Post

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

 

You shouldn't. People will rig demonstrations whenever it is useful to do so. Sony famously demonstrated PS3 "games" that were really CGI (and they have since admitted it - you can check this online.) I was at an Intel conference to show the first AGP bus PCs and the demos given used Voodoo 3D cards.. which turned out not to use the AGP bus, so could hardly demonstrate its advantages. And could spend hours cataloguing the dishonesties of Apple. So, no, you should not assume that a hole in the wall company (I'm guessing that) in an industry notorious for deception selling  potentially incredibly profitable magic tables wouldn't do something deceptive!

 

(For example, you rig the demo by using a CD player that has abnormal vibration problems - due to careful "tweaking" - that go away when you put it on the table magic table - which is magic for the problematic tweaked player, but no other. Magicians do this sort of stuff all the time.)


Edited by scuttle - 2/25/13 at 12:53pm
post #28 of 57
Quote:
Originally Posted by scuttle View Post

 

You shouldn't. People will rig demonstrations whenever it is useful to do so. Sony famously demonstrated PS3 "games" that were really CGI (and they have since admitted it - you can check this online.) I was at an Intel conference to show the first AGP bus PCs and the demos given used Voodoo 3D cards.. which turned out not to use the AGP bus, so could hardly demonstrate its advantages. And could spend hours cataloguing the dishonesties of Apple. So, no, you should not assume that a hole in the wall company (I'm guessing that) in an industry notorious for deception selling  potentially incredibly profitable magic tables wouldn't do something deceptive!

 

(For example, you rig the demo by using a CD player that has abnormal vibration problems - due to careful "tweaking" - that go away when you put it on the table magic table - which is magic for the problematic tweaked player, but no other. Magicians do this sort of stuff all the time.)

i agree, these kind of stuff are actually very easy to be rigged and staged. who knows where the cables lead to and what is going on behind the wall/curtain.
a simple way to demonstrate between the 'clear' and 'muddy' track is to playe them simultaniously and simply switch them using a crossfader


Edited by streetdragon - 2/25/13 at 1:01pm
post #29 of 57
Quote:
Originally Posted by streetdragon View Post

i agree, these kind of stuff are actually very easy to be rigged and staged. who knows where the cables lead to and what is going on behind the wall/curtain.
a simple way to demonstrate between the 'clear' and 'muddy' track is to playe them simultaniously and simply switch them using a crossfader

 

Absolutely,

 

no body knows first off what testers are being subjected to and the laws of physics with precision gear makes it easier to inject FUD into a buyer to convince them especially if the science easily overwhelms most participants.

 

Another unfortunate factor is that even if the experimenter left gear out to be visible afterwards there is no guarantee the rigging wasnt software or something applied that was easy to reverse or 'default settings' after the test.

post #30 of 57

Another simple way of faking a demo like this to use a CD with two copies of the same track - one standard issue, the other poorly recorded. Whenever you watch a demo from anyone trying to sell you something ask yourself if you have seen a professional magician pull off a better trick! Demos are not to be trusted.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
This thread is locked  
Head-Fi.org › Forums › Equipment Forums › Sound Science › Impact of vibrations?