The long-awaited HUMAN 81 DK is now available.
Best viewed in "landscape" mode.
Isolation (or decoupling)
I suppose I am going to take the role of the self-styled "mythbuster" here.
I first started running into mention of this concept in the hifi press decades ago. I'm not sure if they were quoting marketing departments or not, but they would speak of things like heavy foam gasketing between speaker drivers and the cabinets they were mounted in as being for "isolation", or to "decouple" them.
I found this to lack any basis in what our goal is with mounting speaker drivers and complete speakers systems in the listening environment.
The goal is the hold the non-moving parts of a driver as rigidly and as securely as possible relative to the air in the room, and hence to the planet. The "ideal" speaker stand consists bolting it to a masonry pillar extending to the bedrock below.
(Those gaskets were to seal the drivers to the cabinet. I suppose one could say that was to "isolate" the air inside from the air outside. But that's not what they meant.)
By doing this, the maximum amount of the energy dissipated by the speaker would be translated to moving the air in a linear (one-to-one) fashion, and as little as possible to moving the speaker frame or cabinet. This is a basic "action and reaction" type relationship. As the woofer cone moves relative to the magnet structure, we only want air to move in response - we do not want the woofer chassis and, by extension, the speaker cabinet, moving in the opposite direction. By coupling them as firmly as possible to the heaviest object possible, we improve this relationship. This does three things - improves linearity, maximizes efficiency, and reduces or prevents intermodulation distortion of the signals from the other drivers in the cabinet. (That IM distortion occurs when the woofer is able to get the cabinet to move or vibrate).
I have further encountered endless referrals to spikes intended for the bottom of speakers (and other components) as intended to "isolate" them - when their purpose is the exact opposite. Our goal in using them is to firmly place the speaker on the most rigid and unyielding layer of flooring possible - that is, not wobbling around on a carpet, but anchored to the subfloor material below.
If there is then a problem with the floor not being stable, we would either try to move the speaker to a more solid location, or strive to improve the quality of the floor structure. Sometimes moving speakers from one wall to the next, adjacent wall will help, as it changes their relationship to the direction of the underlying joists. Note that high levels of bass energy can sometimes cause floors and walls to vibrate via the air. We would strive to prevent that from traveling to the speakers, or turntable, or anywhere it could cause problems, in much the same way.
There is one area where (mechanical) isolation or decoupling matters - and that is a turntable. Since it features a tiny little transducer designed to convert mechanical change into an electrical signal, which we will then amplify several times to drive our speakers, it is important that this whole machine (or at least the "suspended" platter and tonearm assembly) be set up so it is as unaffected by movement or vibration in the room as possible. We do this by isolating it. By decoupling it from its physical supports, and, if possible, even the surrounding air.
Of course, in general, most stereo (and mono, etc.) components should be disturbed as little as possible by random jarring or physical vibrations. However, the manufacturer put feet on them already that they deemed sufficient for the job. No, really. You do not need to put machined brass cones under your CD player. That's a cult fetish, not engineering.
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