Damping panel vibrations with a viscous membrane

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Anton Shepelev

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Jan 10, 2017, 2:00:40 PM1/10/17
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Hello, all

I am considering employment of the Tecsound mem-
brane:

http://www.texsa.com/en/pl39/productos/id62/tecsound.htm

to the internal surface of my loudspeaker cabinets
to reduce panel resonances. Whereas the membrane is
expensive and a whole roll is too much for my pur-
poses, I think of buying the Tecsound tape, which is
the same material but supplied in the form of 5 cm
(2") tape:

http://www.texsa.com/en/pl39/productos/id67/tecsound-s50-band-50.htm

so I shall have to apply several parallel stripes of
tape to each panel to cover it. Do you think that
will provide the same level of vibration damping as
a solid rectangular piece of the same membrane:

+---------------+ +---------------+
| | | |
| | +---------------+
| | | |
| | vs. +---------------+
| | | |
| | +---------------+
| | | |
| | +---------------+
| | | |
+---------------+ +---------------+

I have chosen the transversal orientation because
the curvature of a panel with a fixed perimeter will
be higher in this direction.

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Scott Dorsey

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Jan 11, 2017, 2:00:08 PM1/11/17
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Anton Shepelev <anto...@gmail.com> wrote:
>Hello, all
>
>I am considering employment of the Tecsound mem-
>brane:
>
> http://www.texsa.com/en/pl39/productos/id62/tecsound.htm
>
>to the internal surface of my loudspeaker cabinets
>to reduce panel resonances. Whereas the membrane is
>expensive and a whole roll is too much for my pur-
>poses, I think of buying the Tecsound tape, which is
>the same material but supplied in the form of 5 cm
>(2") tape:
>
> http://www.texsa.com/en/pl39/productos/id67/tecsound-s50-band-50.htm

My suspicion is that this stuff mostly works by adding mass, and that the
less mass you add, the less it works. It may also provide some reduction
in radiation because of the impedance discontinuity but I suspect that isn't
much.

There would seem plenty of less expensive ways to add mass, some of which
might also add rigidity too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Anton Shepelev

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Jan 12, 2017, 11:21:26 AM1/12/17
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Scott Dorsey to Anton Shepelev:

> > I am considering employment of the Tecsound
> > membrane:
> >
> > http://www.texsa.com/en/pl39/productos/id62/tecsound.htm
> >
> > to the internal surface of my loudspeaker cabi-
> > nets to reduce panel resonances.
>
> My suspicion is that this stuff mostly works by
> adding mass, and that the less mass you add, the
> less it works. It may also provide some reduction
> in radiation because of the impedance discontinu-
> ity but I suspect that isn't much.

In that case it is a rather weak solution to my
problem. I thought it added a good deal viscosity,
and therefore dissipative energy losses as well, be-
cause this membrane is said to be as effective as a
layer of lead of identical surface density, and I
think it is mainly due to its viscosity that lead is
a very effective damper:

http://www.bonavolta.ch/hobby/en/audio/lo_damp.htm

> There would seem plenty of less expensive ways to
> add mass, some of which might also add rigidity
> too.

My primiary objective is damping via energy losses.
Sand-filled sandwiches are excellent but a su-
pererogation for my small cabinets.
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