What is vibration isolation for?


Where do these vibrations come from? From where I stand the earth doesn't shake too badly?! I would think that most vibrations would come via sound transmission through the air directly through the chassis of the components thus rendering the racks or other vibration isolation, uh, useless, no? (with the exception of actual thumping from walking etc)
neubilder

Showing 5 responses by audiofile9

Good tip Piezo, right on! Pbb, here's a thought experiment, that might help understand the possible means by which vibrations can effect the sound of a component.

Firstly, let's consider sound waves, and the energy contained by them. Think about a system running at a "good" listening level, say 90db peaks at 10ft. What does that mean? If your ears are 10' away from the speaker, then some amount of sound energy defined as 90db is hitting your eardrum. Now, just how big is an eardrum? compare that to the surface area of a rectangular box. Then place that rectangular box not 10' away, but between or perhaps right next to one of the speakers. Clearly, the box is receiving many hundreds of times the energy, than the ears are.

Secondly, consider vibrations transmitted from speaker to component through floor, rack, etc. Almost all systems share the same "mechanical ground", and it is usually not a very good one at all - the floor of the listening room - which for most people is a skin of thin layers of wood attached at various points to a lattice of wooden beams. One can imagine that this floor resonates in various manners at various frequencies at various locations.

Clearly, vibrations EXIST. Now, the three more arguable questions: 1) How do the vibrations effect the sound? 2) How can tweaks stop/reduce/change those vibrations? and 3) even if the first two are possible, how could it be audible?

Let's consider how vibrations can effect the sound, in a solid state phono stage for example. A device of this nature is a set of electronic components (transistors, capacitors, etc), SWIMMING in an electro-magnetic field of complex structure. The power supply components, the copper foils conducting current, and the transistors themselves, are bathing each other is em energy. Sure, designers work to reduce the thickness of this soup, but in reality, the "sound" of the phono stage is derived with the effect of this soup already considered. Now comes the imprtant part - MOVE that transistor, within that EM field it is sitting in. High school physics tells us that the very movement will create a current. Thus, if the box is vibrated/resonated in some manner, one can clearly conclude that the electrical signal is being effected to some extent. Next, consider the fact that the vibration is RELATED and caused by the VERY SIGNAL that passed through that transistor some milliseconds ago. The vibration's amplititude and frequency are thus harmonically related to the very signal the transistor is currently trying to pass. Thus, it seems quite clear that "vibrations" can effect the "sound" of a component, and the harmonic relationship may multiply the effect by several factors. So far, we have no conclusion as to whether the "change" is audible or not, but clearly we can conclude that the type of statement "vibrations can not change the sound" is false. Further, I think it is almost impossible to see how these vibrations can FAIL to change the sound.

The physics behind tweaks of this nature are pretty clear. Some of them convert vibrational energy into heat, thereby attenuating the vibration. Others transmit vibrations very effectively, and in theory "remove" vibrations from within a box, and prevent them from "returning" to the box. If a 20lb metal box is well coupled to an 80lb rack, then it will vibrate with less amplitude, and resonate at different frequencies. I can't say much about the removing and preventing return part, but clearly, COUPLING or ISOLATING components will CHANGE the nature of the vibrational problem.

So far then, we have the conclusions that vibrations CAN effect the sound, and that various tweaks CAN change the nature/magnitude of that effect. I would go so far as to change the CAN to WILL.

In terms of actually perceiving the effect, we are back to square zero. I hear it, others don't, and some don't even try, yet proclaim it can't happen. Nothing new there.

Nothing new in this statement by Pbb either: " I find it another thing to assert, based solely on one's personal uncontrolled observations, that HUGE improvements occur for no logical reason. "

The last phrase is clearly false, yet it is thrown around like some ultimate postulate of the universe. The logical reasons clearly exist, and even if we are not currently aware of them, that does not mean they do not exist. (the reasons, not the sounds or perceptions).

"huge" is clearly a relative term. If one has never gotten to know "excellent" wine (like me), the difference between two bottles of similar wines would escape me, let alone the difference after one glass has sat on the table for a few minutes. Yet, a wine connissuer would go on and on about the "huge" differences between those same two bottles of wine, and how one of them needs to decant a little longer. After a little learning and some experience, I would also notice at least some of those differences in the boquet and the body of those wines.

What is getting REALLY old and boring is the attitude "ho hum, you fools are enjoying your circle of mutual masturbation, and who am I to stop your fun. But here I am anyway, with this pamphlet I have about blindness."
Pbb, strawmen, irony, apples, oranges, and lack of knowledge. Thus is a summary of your response, and that of your comments in general. Let me explain.

STRAWMEN
"The problem is you have nothing quantified."
If we consider the spectrum of [ Possible > Probable > Audible ], the thought experiment defines a nice sharp position, somewhere around the right side of the second >. We arrived at that point with incontrovertible logic, whereas your statement of the type ".. for no logical reason" places us somewhere left of the entire spectrum above, and worse yet, does not even define a spectrum.

IRONY
".. for no logical reason" is a statement made for no logical reason, or at least with no logical reasoning put forth. Nor is there any logical reasoning put forth to move the pointer back towards the left even a bit, even though your desired position requires considerable movement all the way to the left.

If by "quantified" you mean "assigned numbers", my thought experiment can be easily turned into a physical experiment. Here's one that requires no lab equipment: Fire up some music with a beat to it. Turn up the volume until you can just begin to feel the bass a little, in your chest (80-100hz does that well). Now, place your finger tips, very lightly, on the top metal plate of your CD player. Do we need to assign a number to that vibration which you will surely feel? If so, buy an accelerometer and a scope, and measure it yourself. Then you could tell us how small those numbers are, and how in-audible that should be. At least then, you could comment with SOMETHING. Something more than the strawmen that you stand up and kick down in such a definitive manner.

APPLES & ORANGES
"As an analogy (for what it's worth) the world is chockfull of bacteria and viruses. Their mere presence does not signify that the carrier is diseased."

Your analogy, upon any inspection, is not worth much at all. It completely fails to anologize the situation at hand. A more accurate analogy would be "someone who voluntarily exposes themselves to high concentrations of very particular bacteria and viruses on a daily basis, may or may not be able to tell the difference between two slightly different diseases."

With that more accurate analogy, you could at least argue numbers. I can imagine something like "if your intra-oral body temperature is exactly 102.6 F, when infected with the nemulo coccus as well as when infected with the nebulo coccus, then your headache could not possibly be different".

Now, the names of bacteria I did indeed make up as I went, whereas the rest is from experience. I find it much more usefull for a discussion to progress along some path, rather than be stifled by the same three mantras repeatedly repeatedly.

LACK OF KNOWLEDGE
"I will trot out the usual question-to-end-it-all (and will probably get the usual stock answer): why would the manufacturers of ultra-high-end transistor amps sold for kilo bucks not build the best isolated chassis possible if this is such a concern? "

That question "ends" only one thing: any shred of credibility of the argument that uses such a statement, simply because it shows the lack of knowledge of the very industry one is discussing. It shows that you have never looked inside a Rowland amplifier, nor a Conrad Johnson tube preamplifier. Nor have you placed the 1 lb mass on the CD in a CEC transport. Apparently, you have not even gone so far as to visit Aria Audio's website (Michael Elliot's new company), to have noticed the images of his circuits with bracing and dampening of the capacitors. Not having done ANY of the above (examples from my very limited knowledge), we can only assume that you have never actually put bubble wrap under your preamplifier, just to prove to yourself that it will not make a difference.

But I guess that would necessitate the owning of a preamplifier, or doing some research, or actually partaking in the hobby that you are so keen to debunk.

It seems you almost had a point with "I don't think we should worry ourselves sick over it...[cut].. When does attention to detail, to minutiae becomes more of a hindrance than a source of advancement? I truly wonder."

But the point is pointless, because "attention to detail, to minutiae" is the VERY definition of ANY hobby or enthusiasm, is it not? Car fanatics discuss the type of alloy used for the screws affixing their front brake pads. Fishing enthusiasts discuss the balance of their fly rod when casting with 10 lb line, especially on humid days. Shutterbugs discuss the dynamics of the sparkle from a car window, given a particular polarization of the filter, color temperature, and film speed. That is what hobbyists do, they pay attention to the details and discuss the minutiae.

What is rather UNUSUAL about the audio hobby is that it seems to attract so many NON-hobbyists, who receive so much satisfaction from constantly telling hobbyists they are barking up the wrong tree.
Albert, indeed we must have been posting simultaneously. Interestingly, our thoughts were as harmonious as our timing :)
Pbb, I hope your hearing ability is not as bad as your reading ability. EVERY assertion you have made in this thread has been addressed and proven to be either factually false, or logically corrupt. Yet, you say "Nothing that I wrote previously in this thread has been seriously challenged."

Are you reading the same thread that everyone else is?
Pbb, your discussion in this thread can be summarized as follows:

"Tweaks can not possibly make a difference".
- well, yes, they can, and here's the physics.

"That's just techno-babble"
- no, it's pretty solid physics, with no contrary theories.

"OK, Tweaks can not make a measurable difference"
- well, here's how you could measure it and tell us what those numbers are.

"You can not possibly hear the difference they make".
- actually, we do. repeatedly, predictably, and 'blinded'.

"No way they make a HUGE difference"
- Pbb, YOU are the ONLY one to use that word in this thread.

"It's like saying every single bacterium diseases someone"
- no it's more like saying some bacteria eaters taste differences.

"Ok, wiseguy, then why don't manufacturers isolate?"
- well, they do, here's a few examples

"Why don't MORE manufacturers isolate?"
- well, here's some more that do.

"Why don't ALL manufacturers isolate?"
- not all products are designed to squeeze the last 5% at 50% more cost
- but for 1-5% of the cost of the product, tweaks can help.

"You haven't proven anything"
- no, because I don't have to. You need to prove the negatives you assert.

"HO HUM. I CAN'T HEAR YOU. LALALALALALALALA"

Please take your childish comments elsewhere, and leave this discussion to users who can a) READ before responding, b) respond to the POINTS raised, c) make claims based upon experience or research, and D) most importantly, actually partake in the hobby being discussed.