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Mechanical Isolation Devices: Myth?

Wombat

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I don't have a carpet, just wood floor. So no spikes, not good for the floor....

Use metal spikes with a suspended timber floor and your loudspeaker will vibrate the floor. Not good.
 

Wombat

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My thought was simple: build some kind of vibration plate that can resonate easily at a certain frequency. We then measure the audio equipment with the plate running versus not. The resonant frequency of the plate ought to travel into the output of the Audio equipment if there is any issue there.

We can then change that frequency of the vibration plate and see if the measured distortion tracks with it.

This would tell us how sensitive electronics are to highly induced vibrations. If there is no trace of it, then nothing that reduces such vibrations would do any good. But we could deploy some if there are measured effects.


Amir, don't you have something like this in your test kit? :D

https://en.wikipedia.org/wiki/Laser_Doppler_vibrometer
 

bona998

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My thought was simple: build some kind of vibration plate that can resonate easily at a certain frequency. We then measure the audio equipment with the plate running versus not. The resonant frequency of the plate ought to travel into the output of the Audio equipment if there is any issue there.

That is very nice idea indeed, because you could see what is going on with audio output in real time on the screen. By adjusting amplitude and frequency of the vibrations you would be able to generate local / global mechanical resonances of specific, crucial parts inside / whole unit (FFT of pure 1khz sinus signal would be great to see, if there are any harmonics / overtones added to the output).

Very interested in the results, so all we need is to borrow programmable vibrations generator now :>
 

SIY

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Or you could do an impulse excitation. This is the 21st century....

My high tech impulse method is tapping around the case while listening to the output or monitoring it on a scope. Unsurprisingly, this has no effect on engineered (rather than "designed") electronics.
 

bona998

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My high tech impulse method is tapping around the case while listening to the output or monitoring it on a scope. Unsurprisingly, this has no effect on engineered (rather than "designed") electronics.

Not so deeply into this kind of technique, will read more about that, looks interesting !
 

Sal1950

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I've got many of these TOTL pieces in my (very large) collection. I've studied their construction, design and sheer engineering prowess over the decades.
Engineers at Sony, etc; are no more immune to expectation bias than anyone else. ;)
One can sell a Popsicle stick and easily get a number of people who swear it make their system sound better if they stuck it in the middle of the

"better if they stuck it in the middle"
Nope,, I won't say it. LOL
 

DonH56

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Have to run, my quick thought is that it is not a myth as much as misdirection or misguidance. As posted earlier, many things within the components cause vibration, and some may be audible, but most are readily measurable (in the right environment and with the right sensors). External influence, at least IME, much less so -- a big honkin' power transformer can hum, but playing a loud test tone at it does not seem to induce a tone on the other side of the power supply. Tubes and turntables are sensitive, of course, and too much vibration could cause a moving transport to hiccup, but by and large IME/IMO the impact of external vibrations on audio gear falls for me into one of those "may be measured but unlikely to be heard" areas.

Sort of like the cable charts showing large variation in performance by extending the frequency response and resolution so that a 0.01 dB riple and -1 dB at 1 MHz looks like a large difference even though in the real world it is inaudible (IMO, or least by my ears).

Note oscillators in audio components, precision guidance, communication systems, etc. are sensitive to vibration and jitter can increase. Whether or not that is enough to broach the audible threshold I could not say, don't have data. Maybe there are studies in the AES? In radar, guidance, and satcom systems I have helped design it is a big problem and vibration testing is a key hurdle to be passed. But I've been looking in the fs to ps range, not the ns range typically audible for things like CD players and audio DACs. And, unless I am fed up and throwing the thing, my CD player will not be experiencing high G's from acceleration like a jet or rocket flying around.
 
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Frank Dernie

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What about speaker decoupling devices? Are spikes enough or even good?
If the speakers are well designed, the enclosure vibration should be minimal, especially if the 2 woofers are mounted on opposite sides. So, how important are speaker stands?
Spikes couple to the floor, not decouple. A device decoupling over the whole audio frequency would have a static deflection of nearly 1" under the weight of the item to be decoupled.
 

amirm

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Sony spent a lot of time and money researching this in the 1980s.
High-end audio companies do a lot of this today. There is a high-end audio company whose name escapes me now that has every PCB mounted on suspension platform in their power amp!

So my point was not that it is not used that way but that it is a common technique from reliability point of view.
 

Frank Dernie

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Amir, don't you have something like this in your test kit? :D

https://en.wikipedia.org/wiki/Laser_Doppler_vibrometer
When I worked at Garrard in 1975/6 we had a R&D engineer working with a very early Laser Doppler device looking at the mode shapes of the complex steel pressings of the inexpensive record decks. Everything was painted matt white iirc and he made some useful mods, I remember him specifying a hole punched into the top plate which changed the mode to substantially reduced the vibration where the arm mounted so anything exciting this particular mode no longer produced an output due to cartridge body moving. The somewhat basic and inexpensive Garrard arms gave substantially less spurious output than the beautifully made SME 3009 Improved contemporary with them.
It was decades before I saw another being used
 

restorer-john

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I'm* about to build a little Arduino based 'earthquake detector' for my son's school science project. It uses the 3(6) axis high gain accelerometers and data logging on SD card to enable looking at seismic events.

The post event analysis can be done in Audacity and it got me thinking the entire project (very compact) could also be used for vibration if I speed up the sampling rate.

Dad's always 'help' with science projects don't they? ;)
 

Wombat

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And teachers mark down accordingly. o_O
 

restorer-john

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And teachers mark down accordingly.

He got to go to UQ in grade 2 to receive a $ prize for his acoustic patterns in various liquids and sands. I was so proud, and to his credit, he did do most of it. He used his iPod to drive a small Class D amplifier and speaker he'd torn out of a ghetto blaster- played various test tones (like Daddy) and took pictures of the patterns in the coloured water, sand, rice etc.. All I had to do was glue it all together and print up his 'journal'.

Poor kid, he's grown up listening to test tones- just like I did. As an aside, I can still recite perfectly (with perfect timing) the test record my Dad used in the early 1970s to 'test' his phono setup. I was scarred- or was that imprinted? ;)
 

Wombat

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He got to go to UQ in grade 2 to receive a $ prize for his acoustic patterns in various liquids and sands. I was so proud, and to his credit, he did do most of it. He used his iPod to drive a small Class D amplifier and speaker he'd torn out of a ghetto blaster- played various test tones (like Daddy) and took pictures of the patterns in the coloured water, sand, rice etc.. All I had to do was glue it all together and print up his 'journal'.

Poor kid, he's grown up listening to test tones- just like I did. As an aside, I can still recite perfectly (with perfect timing) the test record my Dad used in the early 1970s to 'test' his phono setup. I was scarred- or was that imprinted? ;)

A chip off the old wafer. ;)
 
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