charleski
Major Contributor
The only proper data I've seen is an old study by Mullard:
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Mechanical Isolation Devices: Myth?
- Thread starter Spirit84
- Start date
Speedskater
Major Contributor
Mechanical Isolation can be important for:
a] Turntable, tonearm, cartridge combinations.
b] some vacuum tube components.
c] hand held microphone and musical instrument cables.
d] units with some boutique capacitors.
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Loudspeaker are a different topic!
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no well designed modern electronic unit needs Mechanical Isolation.
a] Turntable, tonearm, cartridge combinations.
b] some vacuum tube components.
c] hand held microphone and musical instrument cables.
d] units with some boutique capacitors.
* * * * * * * * * * *
Loudspeaker are a different topic!
* * * * * * * * * * *
no well designed modern electronic unit needs Mechanical Isolation.
I agree, from a common sense viewpoint. Still, if someone can show actual data that isolation makes a difference, I'm interested.
What I had in mind was more in line with the type of testing done for aerospace products and such. Put it on a shaker table and see how (if) the output changes as you crank up the vibrations. For audio, measure the output of e.g. a DAC. Transmissibility data will not be understood by the wider audience, and as noted do not translate directly to audibility. That is a function of the component and its sensitivity to vibration.
Immersing in a sound field as @SIY suggested can be interesting and probably more relevant. A shaker table is usually a low-frequency device. I did sound-field testing in the primordial past when I was trying to optimize my turntable's isolation. I had a "silent track" on a recording and played pink noise on my speakers as loud as I could stand and measured the output from my preamp while the disk spun. Later I helped with something similar for flight-rated oscillators when we immersed them in a sound field as well as doing the usual shaker tests. Pilots get vexed if the radar readout dances around during flight, and the astronauts on the space shuttle had similar concerns. Those were the days...
Immersing in a sound field as @SIY suggested can be interesting and probably more relevant. A shaker table is usually a low-frequency device. I did sound-field testing in the primordial past when I was trying to optimize my turntable's isolation. I had a "silent track" on a recording and played pink noise on my speakers as loud as I could stand and measured the output from my preamp while the disk spun. Later I helped with something similar for flight-rated oscillators when we immersed them in a sound field as well as doing the usual shaker tests. Pilots get vexed if the radar readout dances around during flight, and the astronauts on the space shuttle had similar concerns. Those were the days...
Probably very similar for most tube based electronics.
But the isolation table stuff does little to eliminate contamination from air-born vibrations beating on the microphonic device
The cap's can be microphonic?
Don't remember reading that before.
I'd love to.
Can I borrow your scope?
Thinking about the construction of most caps, I guess it only makes sense.
Well, if that's the case, we won't see any effect. But if the sound field gets transmitted mechanically to the DUT, or if vibration is present in the environment from A/C or passing traffic, then if it's microphonic, we may see some changes. And then, if not, we have good evidence that the effect of the device for audio systems is psychological rather than physical.
Much lower levels. You'll see almost nothing in a tap test under normal use conditions. The same can't be said for PTFE boutique "hand made" caps, which may as well be microphones.
There's a weird audiophile fascination with PTFE, whether in caps or cables. Yet it's a poor choice for either application.
Tapping on something is a good way to diagnose microphonics but doesn't represent a realistic use case for determining the auditory efficacy of isolation devices.
Well, actually it would be quite possible for us to test devices in such way. We once had an industrial client, who was considering to use our isolator for their products. But they wanted to be sure that the final result is in agreement with required specifications. Therefore he gave us the vibration spectrum that was measured at the clients floor, and we should show how our isolator would perform in such condition.
In order to make these measurements, we had to develop our own shaker, and control the vibrations in such a way, that it generates the same spectrum (given in one-third terz band amplitudes) as at the clients place. Then we placed our isolator on top of that shaker, and we could measure how the isolated spectrum would look like.
Reproducing a vibration spectrum with coloured noise is much more challenging than for example just outputting white noise, or some harmonic vibration, which could also be done by it.
Do I understand your intention correctly, and would this help you with your tests when placing the different equipment on top?
-115dB. Not bad at all!
one additional remark that might be interesting, and maybe relevant in this context:
if we used a wav-file of some music recording, and send this as the control signal to our shaker, we could actually hear that music, since the plate of the shaker acted like a microphone. That proves our shaker also works in the audible frequency range, and the amplitudes could be adjusted from extremely small to rather large ones.
Hello Frank,
thanks for this insight. Yes, I can fully imagine that this side-effect is actually welcomed and makes for the characteristic TT sound.
As mentioned above by some others, another path of excitation is through air pressure, and this would still remain even on an active isolator. Consider that the isolator is controlled by active forces, but still is a rather soft mounting. So, the isolator would probably mostly filter out the unwanted environmental noise like foot-fall, air-conditioner pumps, wind-excitation etc. that goes via the floor (at least this is my guess).
But what is for sure, and you confirm this: (active) isolation would never fit for everyone, it all comes down to personal taste
