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Easy tweaks: car damping sheets

[Tar sheets]
[Italian version]

Maybe many of you dear readers already know this stuff: I'm talking about those self-adhesive tar sheets that are commonly used for damping resonancies and vibrations inside cars (both for car audio installations and bodyowrks).

Availability and costs

These sheets are normally 50 x 40 cm large (hey, make your conversions, dudes! The metric system rules :-)) and are easily available at every car spare parts store or car audio installators.
The cheaper ones are those you find at car parts stores: I usually pay 4$ each sheet. Some car-audio sheets are normally more expen$ive, even if very, very, very similar to the cheaper ones ;-)
So, my advice is to buy the car parts sheets as they work fine and cost less (ah, Monsieur Lapalisse...).
Probably you may find something for less since everything is expen$ive here in Italy :-(
Each sheet weighs in an impressive 700 g. (convert, convert...) and has two protective films on each side: one is there to protect the self-adhesive side and the other one to protect the black tar material from fingerprints, even better, to protect your fingers from black stains.
This side has a honeycomb-like pattern, while sometimes is perfectly flat and smooth. The *top* protective film should be taken off once the sheet has been glued to the desired surface.

Why, when and how

There are several different ways to dampen the vibrations and the resonancies of our HiFi components, mainly CD players, turntables and loudspeakers.
Some months ago we tested the Noise Killer, a spray damping compound that works very well when *added weight* could be a problem. We've also suggested to use light self-adhesive cork sheets.
Sometimes we may need a much stronger and heavier action, something that can be detached easily and that can be found just 'round the corner.
So here it is: a sheet of black tar material, HEAVY and able to dampen almost anything, self-adhesive and hence detachable, available at the car parts store nearest to you.
The use of these sheets is easy as it can be: just decide WHERE...
First of all consider your CD player: if the cabinet is prone to vibrate and resonate try placing one of these sheet onto it, even without glueing...you'll be surprised by the damping effect. Of course the glueing is strictly necessary.
Then have a look at your turntable: you can't imagine how many benefits can be achieved by damping resonant cabinets, especially if your turntable is on the cheap side.
To *seek and destroy* the vibrations of your turntable may I humbly suggest you to use a very special HiFi device :-)
Then the loudspeakers: large and thin box panels can play louder than woofers, so a correct damping action has to be taken. Some sheet of this damping stuff can do miracles to the cabinet of your loudspeakers. Of course, every damping action should be verified by means of a careful listening test (before and after the *cure*).

If you feel one sheet isn't thick enough you can try to use two sheets, one onto the other but please be careful: sometimes glueing one sheet over the other isn't easy since the glue on one side seems ineffective on the black tar material of the top side of the second sheet.
There are other possible uses of this stuff: for example you can easily build a bread'n'butter non-resonant shelf by simply making a sandwich of MDF between two tar sheets (MDF being the butter and the sheets being the bread :-) ).

Do they work?

These sheets have been extensively used in the car industry for years, in order to dampen the vibrations of the body panels so imagine what they can do to the resonancies of your HiFi components.
You can be sure that if a cabinet resonates, a sheet of this stuff will silence it. Old and cheap loudspeakers cabinets become sturdy and non-resonant as a modern MDF/wood cabinet.
DO NOT USE these sheets for a suspended subchassis as they can dramatically change the resonancy frequency of the whole apparatus (a TT, for example).
In general, do not use this stuff where weight and mass are a main concern...these sheets are HEAVY, you've been warned.
Finally, do not take for granted that a damping sheet can make your HiFi component sound better...it could sound worse, for some reason.
So my advice is to test-listen to every mod you make, ALWAYS.
Again, don't think that a 3$ tar sheet will turn your cheap Japanese CD player into a Wadia...OK?

Some advice

Avoid applying these sheets over hot parts of your HiFi components or serious damage to the circuits may occour. This material doens't allow a good heat transfer so it should be used only for COLD surfaces (CD players, loudspeakers etc.).
If you want to try it for your preamp/amp first of all discover which areas of the component remain COLD during extensive use and try applying these sheets THERE.
We're not responsible for any damage for wrongly applied sheets. Avoid heat surfaces like the plague! :-)


Looking for a cheap way to dampen vibrations? Look no further...these tar sheets are just for you, provided you learn how to use them properly.
Do yourself a favour: avoid paying these sheets more than they actually cost: some HiFi dealer may try to ask even 20$ per sheet (seen here in Italy...) so you've been warned...open your eyes (and ears) wide...

© Copyright 1998 Lucio Cadeddu

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