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#313667 - 07/07/10 06:24 PM Re: GRAMMA Isolation Riser for Subwoofer? [Re: alan]
Micah Offline
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Registered: 11/16/08
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Loc: Indiana you hoser!!!!
So, the rubber feet under my EP800's don't do that?
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#313736 - 07/08/10 01:40 AM Re: GRAMMA Isolation Riser for Subwoofer? [Re: Micah]
radtek2 Offline
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Registered: 08/05/04
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Loc: Yelm, WA
I have a glass shelf that my VP180 sits on and I used 8 large IsoNode Anti-vibration feet from Bright Star Audio. They are reasonably priced and work well.
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#313746 - 07/08/10 07:10 AM Re: GRAMMA Isolation Riser for Subwoofer? [Re: radtek2]
Griffith Strife Offline
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Registered: 04/09/10
Posts: 64
Thanks Alan I think I get it now. So basically if the sub or speaker is playing loudly. The riser and/or pad would eat the vibes so the surface its setting on would not feel the force. Am I on the right track or still off? Thanks
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#313751 - 07/08/10 08:47 AM Re: GRAMMA Isolation Riser for Subwoofer? [Re: Griffith Strife]
alan Offline

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Registered: 01/29/02
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Loc: Toronto/New York/parry Sound
Hi,

Yes, you're on the right track. And to address Micah's comment about the rubber feet, sure, the rubber feet help. The photo shows the subwoofer with the rubber feet resting on the riser. It's the combination of dissimilar materials that reduces transmitted mechanical vibration to the floor or shelf beneath the speaker, but not acoustically generated vibration elsewhere in the room or even in the same surfaces (the floor and shelf) resulting from the subwoofer or speaker's direct acoustical output.

Some suppression is desirable because you don't want spurious resonances in vibrating shelves, floors, and walls mixing in with the music or dialogue. It can be annoying and distracting; e.g. metal or wooden venetian blinds vibrating at certain frequencies at high playback levels.

The argument for allowing some vibration/resonances is that they contribute to the realism of a musical experience. The best example is a big pipe organ in a church. If you've experienced that, the wooden pew and floor (if it's wood) in the church will vibrate with very deep pipe organ pedal notes and you can feel those in the wooden pew and floor. The same thing occurs in concert halls with deep bass from a symphony orchestra, or even in a club/concert with powerful electric bass. So it's part of the experience, and if that's what you're trying to simulate or recreate at home, then some bass vibration in the floor/furniture is desirable.

By the way, the place where you do NOT want any resonances is in a shelf holding a turntable for vinyl playback or in tube amplifiers. Vibrations in a turntable or tube amp may be transmitted back to the platter/disc and cause feedback. Tubes may become microphonic and pick up mechanical or acoustically borne vibration.

Regards,
Alan

Regards,
Alan
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#313755 - 07/08/10 09:29 AM Re: GRAMMA Isolation Riser for Subwoofer? [Re: alan]
Griffith Strife Offline
old hand

Registered: 04/09/10
Posts: 64
So because my center sits on the top of my shelf, and the Blu-Ray under it. I should think about mopads or something similar, once I upgrade to the VP180. Because the added movement (or resonances) might effect the disks playback. Thank you Alan
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#313783 - 07/08/10 01:37 PM Re: GRAMMA Isolation Riser for Subwoofer? [Re: Griffith Strife]
alan Offline

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Registered: 01/29/02
Posts: 3269
Loc: Toronto/New York/parry Sound
Normally moderate vibration has no effect on any Blu-ray, CD, or DVD optical disc playback, or on solid-state (transistor) electronics.

If the vibration was excessive, then it could perhaps disrupt the laser pickup in an optical player.

Optical players do vary from brand to brand and within different models in terms of sensitivity to vibration or jarring. If a player was unusually sensitive, it could result in audio drop-outs or image freeze-ups or other glitches in playback.

Alan
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