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BILZ Insulation Pad
A very technological material for decoupling feet
Product: Material for decoupling feet
Manufacturer: Bilz vibration
technology AG - Germany
Recommended Retail Price: approximately 10€ per panel depending on size
and thickness
Reviewer: Piero Canova -
TNT Italy
Reviewed: April, 2021
Foreword
Often I happen to read articles expressing very strong opinions about the
performance and merit of accessories for our Hi-Fi systems. Many times the
positions of these commentators are completely opposing and the
consequences are endless discussions. Even leaving aside those comments
based on badly hidden secondary opinions or where partisan positions are
taken regardless of the obvious facts, it is difficult to explain how
people having both a long experience and a true intellectual honesty can
hear completely different results from the same tweak. Perhaps, what's
missing, is a more scientific approach that takes into consideration not
only the modification, but also of what's around it, in short the boundary
conditions.
Today I have decided to venture into the dangerous territory of
decoupling feet. These products, for me, are all those devices that have
the purpose of changing the frequency of the vibrations transmitted by the
shelf where our equipment rests. Since very low frequencies (below 20 Hz)
are outside those we are interested in, if I place an object that has its
resonant frequency in this very low range, it will adsorb the frequencies
of the shelf and will remove the energy without disturbing our music
signal. Normally these feet are made from soft rubbery materials based on
rubber polymers with different fillers or plasticizers to obtain the right
consistency. Some feet use mechanical systems to absorb vibrations such as
springs, either flat or spiral, sometimes with soft materials to lower the
resonant frequency of the spring. The last category is made by feet using
solid materials with a specific crystalline structure like graphite. In my
system, I have a mix of mechanical systems (G-Flex) and soft feet
(Vibrapods). Occasionally also some graphite blocks. How I chose them is
completely random with a perfect application of the “try it and
see” method. What I have now seems to be OK for me, but it is tough to
recommend the same solutions to somebody else. Recently I have discovered
an interesting material I want to introduce you together with the related
documentation, which I think is quite interesting.
A closer look
The problem of vibrations is very interesting, not only in the Hi-End
domain, but also in several industrial and R&D fields. Take, as
example, very high precision scales, electronic microscopes, laboratory
equipment, medical devices and many others. Most of them will produce
inaccurate results if subject to vibrations. The difference is that while
we can, "by ear", find if our system is correctly isolated, you can't do
the same for an electronic microscope so the company selling and
installing them must rely on well-tested and predictable anti vibration
materials. Bilz Vibration Technology AG was established in 1985 and is
specialized in vibration insulation systems of a different kind. Many are
designed for very heavy equipment thus out of our interest, but if you
visit their website you will find some very interesting solutions. My
interest was caught by the "Insulation Pads": they are some greenish
slabs, heavy and of variable size, made from some polymer with several
fillers. I did try to take a picture with my microscope: the image
confirms there are several different materials inside a rubbery matrix,
but you can't go much further.
Among the differentmodels available I have chosen the "B30W" with the
lozenges only on one side: the technical specification is shown here
below.
Insulation
pads B30W
Note
- Bilz
insulation pads can be cut with any circular or band saw.
- We
are happy to supply special sizes on request.
- The
specified maximum load is composed of static and dynamic loading of
the machine. The best insulation effect is achieved at approximately
80-90 % of the specified maximum load.
- Can
also be supplied with a profile on one side (designated for example
B4-1).
- The
stated coefficient of friction refers to conventional industrial
screed.
- Cutting
tolerance is according to DIN 7715/T5, class P3.
Load:
5-40 N/cm², Height: 18 mm, Coefficient of friction: 0.8
Eigenfrequenz
= natural frequency
Belastung
= load
If your last examination in physics was some time ago, the graph above
indicates that applying to one of these panels a pressure (Belastung) of
30 N/cm2 (approx. 29,5 Kg/cm2) will resonate with a vertical frequency of
approximately 37 Hz while horizontally at 19 Hz; if you increase pressure
to 39,2 Kg/cm2 the frequency drops to 34 Hz and 18 Hz. This graph contains
very valuable information: it isn't enough to know the characteristics of
the feet you use, but also how you apply pressure on it. The feet you have
chosen will behave in a very different way if you put on top a 20 Kg class
A power amplifier or a 4 Kg CD player. It is no surprise that you will
have different results and thus different listening impressions are
possible and expected.
The insulation pads can be worked easily with any tool for wood. You can
use a band saw, hacksaw, holesaw, etc. They are almost odourless and do
not mark any surface so you can put them on top of expensive wood
furniture without problems. They have a very high friction coefficient so
your electronics will stay firmly in place. The only problem is that a
pressure of 35 Kg/cm2 isn't very common in High-End equipment, but with a
bit of creativity we can resolve any issues. It is easy enough to make up
a feet of two parts: the first is a piece of Insulation Pad you have cut
while the second is an embedded insert threaded for bolts of varying
sizes. In this way, we reduce the contact area thus increasing the
pressure. If we use three feet each with an M4 screw for equipment
weighing 10Kg, each foot will have a pressure of 27,05N/cm2 so well inside
the requirements of the material shown in our graph. We will have slightly
less than 20 Hz horizontally and approximately 38,5 Hz vertically which is
a fair result. If we use 4 feet each with an M3 screw we will increase
pressure to 36,1 N/cm2 obtaining 18 Hz horizontally and 37,5 Hz
vertically. By playing with number and screw diameter you can manage
systems from 3Kg to 40 Kg which is a comprehensive range for our needs.
How do they sound?
My reference for feet is the G-Flex (see our review), but they are out of production and
they also were too expensive. Vibrapods (see our review) are a bit dark for me, they do
deform in time and if you put them on a painted surface they simply remove
the paint probably because the plasticizer that makes them soft migrates
into the paint. The Insulation pads have the same performance as the
G-Flex, but they are much cheaper so you can make all the tests you want
costing pennies. They do isolate without adding any color to the music, as
it should be. With a bit of proper design, you can also make a version
that can be adjustable vertically so they can be placed below a turntable
or any device that needs accurate leveling.
Defects: I found two. The first is that on the graph the curves tops at
40 N/cm2 and there is no indication of what happens next. They should have
written "kaputt" because above 40 N/cm2 the material breaks and your screw
sinks inside it. If you plan to work in that region be sure you
never put anything on top of your equipment or you will see it slowly
sinking. The second defect is the availability: I have contacted Bilz
Italy and they are super kind, but normally their customers order
industrial quantities so a customer ordering one or two panels worth a few
Euros is understandably a nuisance and you will have to wait until there
is room in their shipment from Germany of the panel you have chosen.
Conclusions
If you are looking for nice-looking feet with
marine chroming this isn't for you, but if you want to isolate your
equipment in a predictable way the Insulation Pads are cheap and perform
very well. With a bit of care and craftmanship, you can make them very
nice looking too.
If you really want the very best and you have
some quite heavy equipment then look in the Bilz website for the air
suspensions "FAEBI 50 Soft + BR7-1". They are the industrial translation
of the deflated bladder under a shelf, but with easy leveling. The
smallest with a load of 9,81 Kg per foot resonates at 6,5 Hz. They are
more expensive at approximately 100€ each and the only device of better
insulating performance is just a maglev system.
DISCLAIMER. TNT-Audio is a
100% independent magazine that neither accepts advertising from
companies nor requires readers to register or pay for subscriptions.
After publication of reviews, the authors do not retain samples other
than on long-term loan for further evaluation or comparison with
later-received gear. Hence, all contents are written free of any
“editorial” or “advertising” influence, and all reviews in this
publication, positive or negative, reflect the independent opinions of
their respective authors. TNT-Audio will publish all
manufacturer responses, subject to the reviewer's right to reply in
turn.
© Copyright 2021 Piero Canova -
piero@tnt-audio.com - www.tnt-audio.com
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