April 2019

A Vibrant Performance
Roger Skoff writes about a different meaning for a common descriptive term.
Article By Roger Skoff

  According to The Oxford Dictionary the word "vibrant" means (among other things) "Full of energy and life", and, when it's used to describe sound, it means "strong or resonating". For High-End audio, either or both of those meanings can apply, and to say that something is "vibrant" can either be a distinctly positive commentary or a description of a problem with our system:

A "vibrant" performance might be a description of music that's strong, emotionally moving, and full of energy. Or two of those same descriptors, "moving" and "full of energy", could be reasons why what we hear from our system is different from the musical reality that we, as audiophiles and music-lovers, are always seeking.

From a system standpoint, what I mean when I speak of "moving" is actual physical movement; not any kind of subjective or emotional response to the music itself. Physical motion is essential to all sound, musical or otherwise; live or recorded. And, while I have no desire to get into an argument with Bishop Berkeley about whether there will be sound if a tree falls in a forest and nobody hears it, it's  certain that  if there is no movement, (falling tree or not) there will never be any sound. It's as simple as that. A vocal cord, a natural act, a musical instrument, or something must move and cause air molecules to move and vibrate an eardrum, a microphone, or something in order to produce original sound, and a playback system of some kind and speakers or headphones (something with a diaphragm or equivalent) must cause air molecules to move again in order for there to be sound reproduction.

Motion is always required. And motion always requires energy. And that's where the problem comes in. According to the Law of Conservation of Energy, energy can neither be created nor destroyed, but can only be transferred from one object to another or transformed from one form of energy to another, with the total amount of energy in a closed system always remaining exactly the same. What that means is that when energy is applied to an object – a loudspeaker diaphragm, for example – some of that energy will be transferred to moving air to create sound waves. Some of which will then, possibly, be applied to moving eardrums and be perceived as sound. Some of it may be applied to moving the loudspeaker that the diaphragm is part of and the box (the enclosure) that  that loudspeaker is housed in. Plus some of it may be transferred (through the box or the air) to the floor that the speaker box is standing on – or may be transferred by the floor or through the air to the LP turntable that's playing the record that's driving the cartridge that's providing the energy to be amplified by an amplifier to drive the speaker that the diaphragm is part of.

And around and around again until all of the energy has been fully dissipated  by creating heat or motion in all of the objects affected.  And, of course, wherever there is a stimulus (as in all that energy circulating around) there will be resonance, with all resonant objects (virtually everything) vibrating (repeatedly moving) at their fundamental resonance frequency and (in declining amplitude for each subsequent order), all of its harmonics.

When the energy transfer from a speaker to a phono cartridge or a microphone is at a high level and out-of-control, it produces a loud wailing sound called "acoustic feedback".  You may have heard it at home from your record player or, at a concert or some other event, from a PA system turned up too loud. You've probably also heard the resonant effects stimulated by and acting upon the sound of your system. Even if they never get to the audible feedback stage, transferred energy and its resultant resonance effects may still be there and be acting to affect your sound. And it's not just from phono cartridges and microphones, either: Some vacuum tubes (either because of a "bad" tube or even a basic design characteristic) may be "microphonic", and will actually create or modify signal to add to the signal they're passing.

This can add "warmth" or even a perceivable "echo chamber" effect, and affect the sound of your system. (As a test, try tapping your tubes with a fingernail and listening for the sound of it through your speakers) Some cables, too, because of the materials they're made of or the way they're manufactured, can also be microphonic. Tap them, too, to find out and can – regardless of any other performance factor – definitely affect (and not necessarily in a positive way) the sound of your system.

Any kind of unwanted acoustic energy transfer or resonant effect can "muddy" your sound and affect your system's tone, imaging, and soundstaging.  So how can you get rid of it? How can you make your system less negatively "vibrant"?  There are really only three basic ways: transference, conversion, and (possibly) cancellation, and the ones most often used usually involve either "coupling" or "de-coupling" the elements of your system from each other and from the affected parts of their acoustical environment.

Coupling means creating a "lock" between two different things, to make them move together, and involves energy transfer for its effect. The most common form of audiophile coupling comes from the cones or spikes ("Tiptoes" and all of their many variants) used under speakers, turntables, or electronics to lock them in a fixed relationship with the surface they're resting on. Doing this means that if one thing moves, the other must move, too. The result of that is that, instead of that of either one, the mass that must now be moved is the sum of the masses of both objects – meaning that the total motion, given any available level of energy, will be lessened accordingly, lessening, also, its effect on your sound. Changing the effective mass to be moved also changes (lowers) the effective fundamental resonant frequency of the "locked" objects, possibly moving it below the lower frequency limits of the speakers, and thereby reducing or eliminating acoustic feedback's insidious effect, even if it's not directly audible.

De-coupling is the exact opposite of coupling and, instead of locking adjoining objects together, seeks to make the transfer of energy between them as difficult as possible. De-coupling devices range from the ordinary rubber feet fitted as standard to most audio components, through the damped metal springs common on turntables, to special Sorbothane or other "feet" intended to provide absorptive motional isolation, and more. Regardless of apparent dissimilarities, however, the basic purpose of all of them is conversion: turning unwanted motion (including resonant or vibratory energy) into heat and thus, while not eliminating it (remember that energy can neither be created nor destroyed), removing its effect from the sound of your system. 

The great majority of these products do work, to one degree or another, and the best of them that I've found to date, whether for speakers, turntables, or whatever else, are the EVPs (Equipment Vibration Protectors) from Norman Varney, of A/V RoomService in Pataskala, Ohio They have not only been highly effective with whatever I've tried them on, but seem, unlike the Sorbothane ones, not to go "flat" and lose their isolating ability over time.

Combination products that claim to both couple and de-couple at the same time, are also available, but – at least to my way of thinking – seem more likely to offer a good marketing strategy than good isolation. That's not to say that they can't work, but only that I have not yet personally experienced it.

One final way to deal with transmitted or resonant energy problems might simply be to cancel them out. As with noise-canceling headphones, devices to do this would have built-in sensors to pick up unwanted energy (movement) and would cancel it with other generated movement of the same kind and amount but out of phase. Muzo and Sono are devices that now claim to be able to cancel externally generated noise in this way, and something similar to them might be possible for use with High-End audio systems. If there is such a thing, you might want to check it out.

Whichever way you choose to do it, reducing the effects of unwanted movement and making the sound of your system vibrant only in the good way is well worth the time and effort. It will definitely improve your listening experience and help you to...

 

Enjoy the music!

-- Roger Skoff