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CEPro -
January 2013
Upselling
Sound Vibration Isolation
to High-End Clients
For
integrators selling high-end audio systems or
to
audiophiles, explaining vibration isolation can open up
a potential upselling opportunity for vibration isolators
for
turntables, tube electronics or CD players.
By
Jim McMahon
The re-emergence of analog-based audio and two-channel
music brings upselling opportunities for CE pros catering
to audiophiles, who are constantly seeking improvements
to their systems: better turntable cartridges, tone
arms, furnishings, etc. Because of the impact of external
vibrations play in the sound quality produced by turntables,
tube amps and even CD players within high-end audio
systems, there's also a chance for intergrators to talk
about - and familiarize themselves with - vibration
isolation.
Vibration isolation in the playback process is crucial
to experiencing high-quality audio. Any external vibration,
no matter how slight, even someone walking near the
turntable or vibration from floor-mounted speakers,
is sensed by the turntables stylus and affects
the sound being played back from the record.Capacitors,
resistors, transistors and other electronic components
used in many audio systems are likewise sensitive to
vibration.
With recorded discs, sound waveforms are captured in
the disc grooves with microscopic undulations. The turntables
cartridge and stylus trace these minute wave forms,
play them back with very sensitive low voltages and
convert them into an audio signal. This is how the sound
captured in the record grooves is reproduced -but this
process is extremely sensitive to movement and vibration.
Vibrations in the range of 2 Hertz (Hz) to 20,000 Hz
will influence the sound reproduction in audio systems.
Vibration within this range can be caused by a multitude
of factors. Every structure is transmitting noise. Within
the home or building itself, the heating and ventilation
system, fans, pumps and elevators are just some of the
mechanical devices that create vibration. Depending
on how far away the audio system is from these vibration
sources, and where in the structure the audio system
is located, whether on the third floor or in the basement,
for example, will determine how strongly the sound quality
will be influenced.
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The vibration isolation platforms from Minus K Technology
are ideal for turntables, CD transports and other sensitive
audio components, and start at $2640
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People who care about sound quality such as audiophiles,
musicians and recording engineers can have very strong,
subjective preferences about what constitutes good sound,
says Eric Jacobs, president of The Audio Archive, which provides
consulting and audio transfer services to digitize, restore
and preserve sound recordings from a wide array of current and
obsolete analog media formats.
Some people like resonances in their system that emphasize
particular frequencies, so they will insist, for example, that
their equipment must rest on a maple wood support because it
has a certain resonance to it that makes the sound more appealing
to them. Others, particularly those engaged in audio restoration
or archival work, want to experience sound as the mastering
or recording engineer intended it, without further coloration,"
he adds.
Enter Negative-Stiffness Isolators
Most manufacturers of high-end turntables recognize that
external vibration is a problem, and will go to great lengths
to minimize it in their turntable designs, says Jacobs.
Quality turntables, for example, are built with superb
platter bearings to minimize rumble..."They often incorporate
high-mass platters that are designed to increase speed stability
and reduce flutter. They might use exotic materials to dampen
vibrations without deadening the sound. Tone arms have their
own set of vibration and resonance characteristics which manufacturers
attempt to isolate from the audible frequencies through geometry,
localized vibration isolation and damping. Turntable designers
go through this elaborate process to try and eliminate vibration
throughout the entire turntable playback structure.
High-end turntables are also sometimes factory-equipped with
built-in vibration isolation supporting the entire unit. But
for the majority of high-end turntables that are manufactured
without factory-installed vibration isolation, third-party air-based
vibration isolators have become a popular accessory. These systems
typically have a vibrating power pump to supply air, with a
tank that holds the pressurized air and delivers steady pressure
to the isolator. The noisy pump is usually located outside of
the room that has the audio equipment, and the air hoses are
run over to the tank and isolating platform.
Air systems are usually a less than optimal set-up,
explains Jacobs. They do achieve some isolation, but we
have found that like most of the mechanical audiophile vibration
isolation devices, they provide limited isolation performance.
They do isolate some usually in one dimension (vertically)
with limited horizontal isolation but they do not isolate
to the extent that is really needed at very low resonance frequencies.
Several years ago, The Audio Archive began an extensive
search for better vibration isolation systems to facilitate
the sound reproduction services that it provides to its clients,
including some of the worlds leading archives, libraries
and record labels.
Having thoroughly tested systems available to the audio
market and generally been unsatisfied, we then looked outside
of the audio world and conducted an in-depth search of industrial
vibration isolation systems, says Jacobs. We learned
about negative-stiffness vibration isolation, which was being
used to eliminate vibrations in ultra-sensitive atomic force
microscopes, and in nanotechnology labs where objects are literally
built one molecule at a time. As we learned more about negative-stiffness
isolators, the more interesting it seemed for audio vibration
isolation.
Developed and patented by Minus K Technology, Inc., negative-stiffness
isolators provide a unique capability to the field of audio
fidelity. The companys employ a completely mechanical concept
in low-frequency vibration isolation. The company employs a
completely mechanical concept in low-frequency vibration isolation.
Where air isolation systems deliver limited isolation vertically
and very little isolation horizontally, negative-stiffness isolators
have the flexibility of custom tailoring resonant frequencies
vertically to 0.5 Hz, and horizontally to 1.5 Hz (with some
products as low as 0.5 Hz horizontally).
Vertical-motion isolation is provided by a stiff spring that
supports a weight load, combined with a negative-stiffness mechanism.
The net vertical stiffness is made very low without affecting
the static load-supporting capability of the spring. Beam-columns
connected in series with the vertical-motion isolator provide
horizontal-motion isolation. A beam-column behaves as a spring
combined with a negative-stiffness mechanism. The result is
a compact passive isolator capable of very low vertical and
horizontal natural frequencies and very high internal structural
frequencies.
What is very advantageous about negative-stiffness isolators
is that they achieve a high level of isolation in multiple directions,
Jacobs says. Not just vertically, which is very important
for audio systems to isolate against footfall, but also in all
horizontal directions. The horizontal direction is often overlooked
because horizontal building vibrations that are transmitted
to the turntable are less obvious.
Improvements in Transmissibility
Vibration transmissibility with negative-stiffness isolators
is substantially improved over air systems, which can make vibration
isolation problems worse since they have a resonant frequency
that can match that of floor vibrations. Transmissibility is
a measure of the vibrations that are transmitted through the
isolator relative to the input vibrations. The negative-stiffness
isolators, when adjusted to 0.5 Hz, achieve 93 percent isolation
efficiency at 2 Hz; 99 percent at 5 Hz; and 99.7 percent at
10 Hz.
Negative-stiffness isolators work with audio systems in
two ways, continues Jacobs. One, they cancel out
large vibrations, what we refer to as footfall. If a turntable
is set up on anything other than a concrete slab floor or other
large inert mass, then every time someone walks in the vicinity
of the turntable, the vibrations from their footsteps are transmitted
through the floor to the support stand and into the turntable,
and finally show up in the recording. People will literally
tiptoe around their audio playback systems, but the playback
process is so sensitive that it will still pick up footsteps
in the hallways or rooms some distance away. And two, the negative-stiffness
isolators block out building vibrations in the higher audible
frequencies.
Transmissibility of negative-stiffness isolators is also improved
compared to active vibration isolation systems. Also known as
electronic force cancellation, active isolation uses electronics
to sense the motion, and then adds forces electronically to
effectively cancel out or prevent it. Some active isolation
systems can start isolating as low as 0.7 Hz. But active systems
have a limited dynamic range that is easy to exceed, causing
the isolator to go into positive feedback and generate noise.
Although active isolation systems have fundamentally no resonance,
their transmissibility does not roll off as fast as negative-stiffness
isolators.
And then there is the sound, which is what really matters
most to our clients, continues Jacobs. With negative-stiffness
isolators there is a sense of harmonic rightness. Instruments
sound much more like real instruments, and voices sound like
they are in a real acoustic space, with real air around them.
The ability to see clearly into the entire three-dimensional
soundstage is greatly enhanced. Improvements in rhythm and pace
are captivating. Negative-stiffness isolators truly represent
a significant advance in sound quality for high-end audio.
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