Origins, Effects, Solutions
Little has been written concerning the effects of vibration
on high-end audio components. I am surprised. I feel that
the effects of this very important, little discussed and
almost unknown topic is detracting from our listening pleasure.
Unwanted vibrations have a serious, adverse impact on the
performance of most, if not all, modem audio and video equipment.
The reduction or removal of these vibrations can significantly
improve the resolution of every system. I offer my observations
on the topic in the hopes that you may enjoy some of the
same improvements I have gained in my own system from the
implementation of the methods to follow.
All of us have seen attempts at vibration control. Soft,
resilient feet, spiked feet, cones, isolation bases, turntable
suspensions, tube damper rings, etc., are just a few of
the many ways manufacturers deal with the vexing problem
of vibration control. Here, we will examine each in the
context of their specific contribution to the control of
unwanted vibrations. But first, let us explore the interesting
and complex phenomenon of vibration itself.
The vibrations that cause us such great concern, are those
that comprise the very nature of our hobby - sound. Our
loudspeakers produce sound by the motion of their drivers,
creating compressions and rarefactions of air molecules
within the room. The eardrum vibrates in sympathy with these
modulations of the air. Electrical impulses are sent to
the brain, and there interpreted into meaningful, recognizable
In the same way that the modulation of the air causes
our eardrums to move in sympathy, so to they produce motion
in all objects they encounter. If the amplitude of these
motions is sufficient, and vibration within the component
occurs, audible degradation results. Therein lies the rub.
Two major types of vibration will occupy our discussions.
These vibrations reach our equipment via two distinctly
different paths, hence their names: structure borne and
air borne vibration. Structure borne vibrations enter
through the shelf or platform upon which the component rests.
Airborne vibrations are the results of fluctuating air currents
produced by the loudspeakers, which vibrate the enclosure
of the component.
The two types of vibration differ considerably in terms
of the methods necessary to control them. First, let us
examine air borne vibration, it is created, and how we can
deal with it.
As we have seen, a speaker produces sound by moving air.
Sound within the room causes vibrations-and/or resonances
in the chassis, circuit board (s) and individual component
parts of all electronic equipment. These vibrations induce
various distortions in the signal, causing a masking or
veiling of the music to occur. Audiophiles have long been
aware of the sensitive nature of tubes and tubed electronics
to vibration. This condition has been termed microphonics
when applied to the tube itself. Indeed, simply tapping
on the glass envelope of a vacuum tube, or on the chassis
of a very sensitive unit, produces audible emanations from
the loudspeakers. In much the same way, but on a smaller
scale, air borne (and structure borne) vibrations will subtlety
affect the sound produced by these units.
In the same way vacuum tubes are sensitive to external
vibration, so to I believe, solid state and passive components
are too. Capacitors (in particular), resistors, transistors
and the like are sensitive, at least to some degree, to
the influence of vibration. More and more we are seeing
designers take these concepts into consideration when designing
a new product. Chassis damping, improved structural rigidity/integrity
and individual component damping are now almost commonplace.
Physical orientation (i.e. placement within the room)
may well be the most crucial aspect in reducing unwanted
colorations induced by air borne vibration.
The areas of greatest air pressure (hence the loudest
sounds), will be the worst areas for placement of sensitive
equipment - especially CD players and turntables. Ultimately,
placement of all sensitive components in a room separate
from the speakers would be ideal. If this approach is practical
in your situation, I would recommend it. Short of that,
keep your equipment out of comers and as far away from the
loudspeakers as circumstances permit. Additionally, be sure
that you select a stable non-resonant mounting surface for
all your components. We will examine this aspect in more
Structure boom vibrations affect equipment in much the
same way as do their air born counterparts, and generally
to a greater degree. These vibrations create various colorations
and distortions that blur or veil the music, confuse the
image and generally wreak sonic havoc. Luckily, the control
methods necessary to deal with structure born vibrations
are more straightforward, and easily employed, than those
measures needed to manage air born vibration. In general,
all we need to is effectively isolate the equipment from
its resting place. While it may prove difficult to totally
eliminate all structural vibrations, we can significantly
reduce them with some simple to use, and readily available,
techniques and materials.
We can divide resonance control and isolation products
into three categories based on their mode of operation.
Coupling, de-coupling and energy conversion
Coupling devices tightly marry the component to
the shelf. They include cones, spikes and the like. Spikes and cones, by decreasing the contact area with
the support, (theoretically) act as a mechanical diode - allowing vibration
to travel away from the component, while limiting the return
path. New materials now available (composite, ceramic,
carbon fiber) seem to have improved cone performance over
metal cones of the past.
De-coupling devices attempt to isolate the
component from its resting place, usually with soft,
resilient materials. Most audiophiles are familiar with soft de-coupling feet.
These pliable, resilient, rubber-like pucks absorb vibrations,
converting their motion to heat, dissipating their effect. Vibrapods are the most common today, their predecessors
included Sorbothane (Audioquest) and NAVCOM (Sims Vibration
Dynamics). Magnetic isolation is a form of de-coupling and
this technology has been popularized by the Clear Audio
Energy conversion products convert mechanical
energy to heat. Though soft de-coupling materials perform a
similar function, there are energy conversion devices on the
market that do not use viscoelastic materials. The best
example are the Stillpoints. Some of most effective devices
on the market today, Stillpoints Ultra Stainless Steel
isolation footers can offer significant sonic improvement.
At the manufacturing level, damping of equipment chassis and
isolating internal components from vibration can
offer truly amazing sonic results. Manufacturers are just
beginning to scratch the surface of this very important
aspect of equipment design/construction. In most designs,
vibrations in the cabinet and/or chassis are readily transmitted
to the sensitive circuitry within. These vibrations are
the cause of quite serious sonic aberrations that significantly
limit the sonic potential of the component. One might consider
experimenting with surface mounted materials to damp chassis/cabinet
resonances. The application of surface damping to the larger
metal parts of equipment enclosures can greatly reduce vibrations
and improve sound quality.
Sheets made from EAR Iso-Damp or Q-Pads can be applied
to a variety of surfaces to provide damping. Some are available
with adhesive backing, others can be attached with contact
cement or simply applied without adhesive for temporary
Another more elaborate method of surface damping employs
an exotic material (borosilicate) that is applied like paint,
hardening to form a stiff non-resonant barrier to mechanical
vibrations. This approach is most often applied to the inside
of loudspeaker enclosures as a means of increasing the rigidity
of cabinet walls and thus reducing resonant modes. The effects
of this treatment will vary with the material used, the
enclosure quality and the uniformity of application. Totem
uses this type of material in the construction of their
As mentioned previously, I believe capacitors, resistors,
transistors and other component parts are sensitive to vibration.
Therefore, anything we can do to reduce vibration in these
components could be sonically beneficial. To this end, we
shall explore a few of the options available for the more
ambitious tweaks among you.
Capacitors, in particular, are sensitive to mechanical
vibration. A few manufacturers attempt to control extraneous
movements by gluing these parts to the circuit boards. This
method, however, will only be effective if the circuit board
has been effectively decoupled from the chassis. This usually
is not the case. Alternately, damping the part itself by
the application of surface treatments has proved beneficial.
Strips of Q-Damp or Iso-Damp are well suited to this task.
If you are so inclined, experiment by placing small strips
of damping material on capacitors in critical areas of the
circuit. Additionally, you may want to consider isolating
and/or damping the circuit board itself. This measure is
especially effective in the case of tubed electronics. Note:
One should only attempt these modifications if they feel
comfortable with the task.
Another method often reported as effective in tubed gear
involved the use of tube damper rings. These compliant rings
are placed around smaller signal tubes to damp vibrations
in the glass envelope. Several varieties are available,
each with its own set of advantages and drawbacks. Wider
designs do a good job of damping due to the large contact
area. The larger contact area however, leads to increased
internal envelope temperatures that may significantly shorten
tube life. Smaller cross-sectional rings made of rubber
avoid the heating problems, but do a poor job of damping.
We have adopted a unit featuring a small cross-section,
but made from high temperature silicone that exhibits good
damping properties. The silicone acts as a bit of a heat
sink, actually drawing heat away from the tube.
To further isolate tubes, a special isolated socket has
been produced by the Canadian firm PEARL. The Iso-Socket
is designed to replace existing seven and nine pin sockets
with a de-coupled unit employing silicone foam or Sorbothane.
These devices do an excellent job of isolating the tube
from structure-borne vibrations. Their use however, does
require soldering, and so should be left to qualified individuals.
Additionally, this and other electrical modifications should
be considered in the context of their effect on the manufacturers
warranty. This procedure may void your warranty, check
with the manufacturer if you have any questions.
A major factor in determining the amount of effect that
vibrations will have on our components, is our choice of
audio furniture. The stand or rack that we use to support
our equipment can either contribute to or reduce the effect
of these unwanted vibrations. A variety of designs employing
many different materials are available. I personally prefer
the rigid, open frame variety as they provide a very stable,
rigid and relatively non-resonant support. Fully enclosed
cabinets may exacerbate the problems caused by air-borne
vibration by creating a resonant chamber around each component.
Additionally, these units are most often made from wood,
which offers and inherently less stable support. Some rather
serious audiophiles have gone to the extent of providing
heavy blocks of concrete, marble or granite to support their
equipment. While no doubt very effective, this radical and
expensive method is likely to prove impractical for most
listeners. As a rule of thumb, anything you can do to increase
mass and/or rigidity will reward you with sonic improvements.
The Stillpoints ESS rack pictured combines energy
conversion technology with a rigid, non-resonant frame and
The easiest way to isolate a component from structure-borne
vibration is by sliding an isolation base beneath it. A
host of superb products exist to reduce the effects of structure-borne
vibration and dissipate internally generated vibration.
These include Gingko, Silent Running, Symposium, Bright Star, Townshend, Arcici, Signal Guard,etc.
Pneumatic isolation has become popular in the past,
popularized first by Townshend then by Bright Star and Arcici
and the Vibraplane. These devices are extremely effective
barriers to the extremely difficult to control low frequency
In cases where the amplifier is to be located on the floor
near the speakers, amplifier isolation bases are highly
recommended. Tube and hybrid gear will experience the greatest
improvement, but solid state equipment is likely to benefit
as well. The practical aspects of improved air circulation
(for better cooling) and the enhanced cosmetic appeal that
these bases offer, should not be overlooked. Most use spikes
to insure tight coupling to the floor.
Speakers, the component responsible for producing the
vibrations we seek to quell, require careful placement techniques
to insure best performance and least interference. Spikes
have become the favored method of "mounting" speakers.
These devices can be particularly effective when the speakers
are to be placed on a concrete slab foundation. Here, the
great mass of the concrete slab serves as an effective "sink"
for the vibrations created by the motion of the loudspeaker
enclosure. Hard-coupling speakers (using spikes) to a suspended
wood floor however, can, in some cases cause problems. The
floor can act as a kind of "sounding-board," set
into resonance by the vibrations of the speaker. Some listeners
find decoupling the speakers from the floor improves performance
under these conditions. Vibrapod's are an easy solution,
but some speakers are not stable once perched atop these
feet. In those cases an isolation platform offers a more
stable footing, to which you can spike your speakers, if
desired. Any of the makes mentioned previously work very
well, just be certain the platform is designed to support
the weight of your speaker. For the do it yourselfer's out
there, make your own isolation platform by sandwiching two
pieces of rigid material like MDF (a high density wood fiber
product), Corian or, for special situations, granite or
marble, with a layer of damping material or Vibrapods in
Designers and Engineers are only just beginning to explore
new methods of improving the sound quality of the equipment
they manufacture through the application of vibration control.
As with many other ideas, the curious audiophile is likely
to find significant improvements through experimentation.
Take the time to employ some of the ideas discussed here
and I think you will find new levels of performance lurking
within your system, just waiting to be discovered!
1) Do not place equipment in comers or directly behind
speakers, especially planar designs.
2) Locate components and loudspeakers on a rigid,
non-resonant support. Avoid enclosing equipment in cavities
that will act as resonant chambers.
3) Experiment with cones, soft decoupling feet or
isolation feet or bases under all components.
4) Consider placing floor mounted amplifiers on
5) Experiment with tube damper rings and/or isolation
sockets on tubed electronics.
6) If you enjoy more advanced projects, consider
damping internal circuit components, circuit boards and