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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Seismic Isolation for Loudspeakers (Bound and Gagged No More!) posted by bdiament on December 30, 2002 at 07:33:40:
i experienced the same, BTW without increasing mass, marble bases etc. I use the Daruma 4s, but had similar results with other forms of floating / rolling supports. A similar effect can be had by supporting the main weight of the speaker (or other equipment) on one spike (eg. under the front) and balance (eg. the opposite) corners with felt pads, or a central spike with four felt pads.My take on explanations: The effect has indeed to do with Doppler distortion, but it is more complex than already stated.
'Rigid' coupling with eg. spikes is never rigid. The surface and spike form a resonating (*relatively* stiff) spring / mass system. Increasing stiffness simply shifts structural resonances *up*. Such resonances produce Doppler distortion or FM modulation side bands in the ears, around *every partial tone* of the sound . The higher in frequency these resonances (distortions) are, the further harmonically they separate from the (undistorted) partial tones of the sound, and the less they are masked by their partial tone. This effect is most audible in the lower ranges, but it pertains across the audio band. The better audible, the more complex the harmonic spectrum.Making an educated guess, i would propose optimally stiff supports resonating in the sub 200 Hz range at max. ( extremely stiff !) midst in the upper bass / lower midrange. Roller bearings resonate maybe between 0.5 and 6 Hz.
The stiff support resonance is energized all the time, laying in a very important and densely orchestrated musical ranges.
The ELF resonance is practically not energized, and if, its audibility is very weak.To my ears it really sounds like the ' harmonic space' between the partial tones is much widened, less clogged.
It sounds also like structure born feedback is eliminated, which makes sense too, because *some* SPL induced vibrations are eliminated too by floating the speakers.*Simplifying* the resonant modes play a role too: Support eg. on one spike allows only very simple slow, damped pendulum-like movements. Stiff supports let the speaker jump around busy in several planes, rocking modes etc, without much damping, and therefore different spikes damping properties are very audible too.
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Follow Ups
- Doppler effect, spectral side-bands - Arbelos 13:00:45 01/01/03 (9)
- Re: Doppler effect, spectral side-bands - bdiament 13:24:27 01/01/03 (8)
- Re: Doppler effect, spectral side-bands, spikes - Arbelos 16:48:32 01/01/03 (7)
- Re: Doppler effect, spectral side-bands, spikes - bdiament 07:07:01 01/02/03 (6)
- Speaker supports, FM modulation & browsing audio science books... - Arbelos 15:17:54 01/08/03 (5)
- Re: Speaker supports, FM modulation & browsing audio science books... - bdiament 16:30:57 01/08/03 (4)
- Velocity, Doppler formulas, other forms of FM distortion - Arbelos 15:01:20 01/11/03 (3)
- Re: Velocity, Doppler formulas, other forms of FM distortion - bdiament 09:52:59 01/12/03 (2)
- Re: Velocity, Doppler formulas, other forms of FM distortion - Arbelos 12:10:17 01/12/03 (1)
- Re: bearings - bdiament 14:41:07 01/12/03 (0)