.....and those current induced mechanical vibrations in AC positions are producing f2 harmonics.
I made previous mention of sonically loud amplifiers and got laughed at...now there are sensible same observations......ever notice how the sound of a phono system changes when the cover is closed down.....the stylus assy produces natural sound that is well audible across the room, and still actually audible with the volume turned up....even turned up loud.
These low level 'natural' sounds add to the 'in room' sound when a hifi is played and interestingly these 'mechanical/natural' sounds can be heard distinctly separately from the reproduced sounds issuing from the speakers.
Another observation is that when working at live shows and standing outside of and slightly behind the foh pa speakers, natural vocal sounds can be clearly heard coming from stage despite the racket booming out the back of the foh speakers only 2-3 metres away.
Most high gain audio stages will emit spurious output when components are vibrated, and the character of these emitted signals can be totally unmusical...nasty.
Eric.
I made previous mention of sonically loud amplifiers and got laughed at...now there are sensible same observations......ever notice how the sound of a phono system changes when the cover is closed down.....the stylus assy produces natural sound that is well audible across the room, and still actually audible with the volume turned up....even turned up loud.
These low level 'natural' sounds add to the 'in room' sound when a hifi is played and interestingly these 'mechanical/natural' sounds can be heard distinctly separately from the reproduced sounds issuing from the speakers.
Another observation is that when working at live shows and standing outside of and slightly behind the foh pa speakers, natural vocal sounds can be clearly heard coming from stage despite the racket booming out the back of the foh speakers only 2-3 metres away.
Most high gain audio stages will emit spurious output when components are vibrated, and the character of these emitted signals can be totally unmusical...nasty.
Eric.
Jan,
You know perfectly well there is a difference between claims that the signal in a properly constructed capacitor will induced mechanical changes and that external forces will induce changes in the capacitor.
If anyone has any doubts hook up a charged capacitor to any variation of an oscilloscope and tap it.
When a capacitor is used in a loudspeaker crossover and is in the same cavity as a driver (think woofer) it will receive much more excitation. I also measured the acceleration on the outside of a small 2 way loudspeaker. Not surprisingly those levels were well above what is found as a normal baseline.
So there are two approaches to reducing vibration induced intermodulation distortion in crossover capacitors. You can use essentially rock hard parts or isolate them from vibration. Of course you can do both.
ES
Well, at least some people believe in SOMETHING! I am glad that some here have tried different caps and found that the 'undamped' ones are problematic.
Many audio designers take this very seriously. Usually, the common finding for a .01-.47uF capacitor is a polystyrene-tin film, properly fabricated, with copper leads and a good end construction. When you 'bonk' them, they go 'thud', rather than 'ding'!
It is also amazing how few 'exotic' caps are used. Just plain industrial audio grade caps, although sometimes the audio manufacturer will buy enough to allow his logo or part number on the cap, and the outside wrapper may be a different color.
I find EQ and power supply bypass caps the most important. Of course, I don't personally design coupling caps in, but they would be at least as important as power supply bypass. I don't know why power supply bypass is so important, but that is one of the main changes in the Parasound amp design from the HCA-3500 to the JC-1 power amp. It is like changing tire brands on a sports car. Of course, you have to have owned a good sports cars and changed the tire brand to believe this too! '-)
Many audio designers take this very seriously. Usually, the common finding for a .01-.47uF capacitor is a polystyrene-tin film, properly fabricated, with copper leads and a good end construction. When you 'bonk' them, they go 'thud', rather than 'ding'!
It is also amazing how few 'exotic' caps are used. Just plain industrial audio grade caps, although sometimes the audio manufacturer will buy enough to allow his logo or part number on the cap, and the outside wrapper may be a different color.
I find EQ and power supply bypass caps the most important. Of course, I don't personally design coupling caps in, but they would be at least as important as power supply bypass. I don't know why power supply bypass is so important, but that is one of the main changes in the Parasound amp design from the HCA-3500 to the JC-1 power amp. It is like changing tire brands on a sports car. Of course, you have to have owned a good sports cars and changed the tire brand to believe this too! '-)
Ed, it's usually expressed as cm/root-Hz gravity itself does not fluxuate. My reference has it rolling off as 1/f**2 so it's pretty far down at audio frequencies, like 10-11 cm/rt-Hz at 1kHz. That's backround noise, you guys are off talking about making sound with capacitors. Which leads to the usual results, If I put 100V rms on a cap the one that emits the least noise is the best for my 10mV rms circuit application.
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John,
Actually, if you do not use "visible" coupling Cap's, you still need to fit them, except they are now called "power-supply" capacitors. No matter how you do it, it is practically impossible to remove capacitors from the signal current loops.
Which is why I normally have few qualms about using coupling cap's.
Anyone know some affordable 1,000uF Tinfoil and Polypropylene capacitors for my powersupplies, small size would be nice?
Ciao T
Actually, if you do not use "visible" coupling Cap's, you still need to fit them, except they are now called "power-supply" capacitors. No matter how you do it, it is practically impossible to remove capacitors from the signal current loops.
Which is why I normally have few qualms about using coupling cap's.
Anyone know some affordable 1,000uF Tinfoil and Polypropylene capacitors for my powersupplies, small size would be nice?
Ciao T
Scott,
In the practice of acoustics we use "G" as the reference. These are issues I have measured and published. So far I haven't been confronted with the usual evidence of my errors.
I seem to be unable at the moment to attach my baseline measurements, but I will when that feature starts working again.
Funny thing I was asked to review some tinfoil capacitors until I asked for 300uf samples! Never heard anything again.
I suspect nothing would have happened until a "Name" copied me.
Hi,
Affordable per uF - like 1 Euro per 1,000uF?
My point was a bit more subtle, actually.
I can arrange a circuit to be "DC coupled" and bring the cheap electrolytic power supply capacitors and the power supply regulators into play.
Instead I can design for maximum isolation from the supplies and accept a coupling cap, which I can actually afford in terms of cost/size...
Now, I wonder, which design would be the better one?
The one that is "DC coupled" but essentially coupled through cheap bigass 'lytics, or the one that uses a good quality coupling cap...
Ciao T
Affordable per uF - like 1 Euro per 1,000uF?
My point was a bit more subtle, actually.
I can arrange a circuit to be "DC coupled" and bring the cheap electrolytic power supply capacitors and the power supply regulators into play.
Instead I can design for maximum isolation from the supplies and accept a coupling cap, which I can actually afford in terms of cost/size...
Now, I wonder, which design would be the better one?
The one that is "DC coupled" but essentially coupled through cheap bigass 'lytics, or the one that uses a good quality coupling cap...
Ciao T
I got all your articles (2009-2010) yesterday which one. No problem I was speaking of physics the only reference I have. Seismometers operate at many orders of magnitude less than that (.005G). Gravity wave detectors at 10-21G. I was reading a paper this week that had a preamp measuring .5nV down to .1 or .01 Hz that had a .18F Nichicon super cap in the signal path!
Maybe you guys just turn it up too loud.
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Yes, one is microphony and the other is speakophony
You are right of course.
BTW, I have this Siemens K2207 'contact fehler suchgeraet' which is designed to find exactly these things. It sends a signal through a component or contact (switch, relay, connector) and then you tap it (the DUT) with a small plastic mallet.
The change in signal level is demodulated and indicated and also made audible. Freq range is 3kHz to 12.5MHz.
Unfortunately, I don't have the mallet anymore.
jan
You shouldn't waste your time on my stuff, just read all the other folks stuff. The article on vibration ran in Elektor. It was slated for AX but at that time Ed Dell want to give Elektor some U.S. content for their new North American edition.
I did not measure any super caps to see what their excitation level was. The audio conclusion was that if you place a phono preamp on top of the case of a full range loudspeaker you will be at the threshold of what may be heard.
On fellow I spoke with to confirm the baseline vibration level got his data from finding the best sites for semiconductor fabs! Now if you bury a gravity wave detector in a deep mine you most likely have a lower level. Of course they are looking for signals, I would be curious to know what their baseline noise level seems to be, or not!
However in reviewing my article I see some interesting results I did not notice at that time!
Which issue, I might have it? You can basicly watch the waves hitting the shore in LA from a mine in South Dakota. I believe you measured what you measured, but as you say the slightest common sense eliminates the problem. I think BTW a stylus placed down on an LP (not spinning) would make a nice tuned vibration detector at ~10Hz.
I build this first as an inductive phonosatge for ETF2010. The first prototype was build with a big air coil. It was so sensitive that i could even hear the motor cogging in my Spiral Groove turntable and i could hear the noise it makes when the seem of the silicon string hits the pulley . Later i substituted the air coil with a small transformer in a Mu-Metall can and then it worked quiet as an MC phonostage. That also solves the problem that transients from tick and pops on the record cause.
Take the innards out of a car ignition coil, amplify the voltage appearing across the HT connections and you have a marvellous magnetic pick-up tool.
Electric trains starting and stopping way down the line can be heard 100m from the power lines, crt tv's can be picked up 10m away and loudspeakers emit audio modulated magnetic field easily detected 5m or more distant.
Go for a walk around your house or neighbourhood and be astounded at the levels and sources present.
Eric.
The problem is some folks don't believe that without doing any measurements. If you have a low end system it probably doesn't make a difference. But yes something as simple as the connection of your loudspeaker to the building structure can be measured.
As a simple example, in my office are corner horn loudspeakers. Not surprisingly they slowly move out of the corners. Either it is poltergeist, the very rare cleaning, or vibration induced movement. When spiked feet are used they either have stopped moving, can be repositioned after cleaning by feel into the floor dents, or the sharp points scare off poltergeist. Please choose whichever explanation you prefer. But the result is proper placement in the corner has a very large effect on the way the loudspeaker performs.
You are free to choose if that is from smoother low frequency response, better time alignment over frequency, change in SWR @ some LF, stiffening of the cabinet or just psychological phenomena.
Placing electronics on a solid platform also has an effect, you can choose from reducing vibration introduced noise from capacitors, magnetic flux changes, reduced data errors down to modulating the I/O connectors contact resistance. Or please feel free to add your own theory.
The issue is to isolate and measure what is actually happening so that you can then make decisions as to how to get the best result.
Of course best results can mean results per dollar, sound that you prefer, to what ever you want.
That does not mean all audio issues are just opinion. If you tell me a Radio Shack Minimus 5 is the best loudspeaker you have ever heard, that actually could be correct if the only other ones you ever heard were in ceilings in fast food restaurants. If you tell me you have listened to all of the "audiophile" loudspeakers and still prefer it, I will assume you are deluded because it ain't possible to have listened to them all. If you tell me you have compared it to several well known decent speakers and it is still the best, then quite simply you would just be wrong!
But the most important issue is that for most here this is a hobby so HAVE FUN!
Scott
Elektor did surprise me by not changing the title I would have used in AX. It was "My Friend the Accelerometer." Google'n that brought me right to June 2010! I thought I had sent you the article. It was the one with the woofer shaker table.
ES
As long as sharpening down a 15 cent Home Depot screw does the same trick. Corner horns not sounding right when moved out of the corner is probably not the best example.
OK, I have it.
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