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Old 26th September 2012, 03:31 PM   #1271
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by SY View Post

The product of the electronic transfer function and the mechanical one will be unity, so no overall energy storage regardless of forcing function and its frequency. Again, single valued functions...

SY, I think jneutron says eccentiall the same think but I'll try as well.
Would you be satisfied from the result of applying a pre equalized signal to your speakers to compensate for one room acoustic resonance(assume perfect match of fo and Q)? The two systems are loosely coupled there too.

Is there any technical criterion in such a case by which one can be guided to equalize one resonance but not try to electronically equalize another?

George
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Old 26th September 2012, 03:35 PM   #1272
bcarso is offline bcarso  United States
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Originally Posted by gpapag View Post
Chris, I will help you with the public exposure (I can share the tar)
For a tip with an effective mass of 0.27mg (Denon DL-103)following a theoretical groove with an 20KHz triangular 5cm/sec modulation, the resulting peak acceleration is 10,000m/sec^2 (1020G).
The inertial force due to this acceleration btn tip side and wall land would be 0.0027N.

Increasing by 20db the modulation velocity to 50cm/sec, these numbers are multiplied by 10.

In a more common case (1KHz at 5cm/sec) acceleration drops down to 500m/sec^2 (51G) and force is at 0.0000135N

I am sure that calculations based on tip dynamics will give wild peak temperatures but wouldn’t published images prove any thermal induced evidence at the groove lands, if that high temperatures were really occurring?

http://www.synthgear.com/2010/audio-...on-microscope/


George
That's a beautiful link George ---thanks for that.

I used to visit a chatroom on Stickam, associated with the very popular Hank & Jim Radio Network, and at one point another person asserted that vinyl records encoded bits in the grooves --- directly! He mentioned that he was an attorney, and I expressed relief that I was not his client.

I again have to remind us that we're talking about the stylus tip and not the grooves getting to these extreme temperatures. And as far as I know we haven't found a reference yet that backs up the assertions. It may turn out to have been someone's speculation that took on the aspect of a scientifically sophisticated urban legend and propagated.

"The Moving Finger writes; and, having writ,
Moves on: nor all your Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all your Tears wash out a Word of it."

The question of what a patch of vinyl gets to during the traverse is certainly interesting and important, but it's not identical to the tip temperature. Also, a before-and-after would be fascinating, and in the comments in the link an electron microscope is mentioned that does not require the plating operation for viewing the sample. Identifying where one was on the record might be tricky, for the comparison of before and after.

Another nice touch would be to show a scale for the wavelength of red light, or a multiple of same, as an inset in some of the higher-magnification pictures. Many tend to short-sell what a stylus is really doing, and tend to think of light as a finer probe than it is. One micron is pretty big.
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Old 26th September 2012, 03:38 PM   #1273
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jneutron View Post

The "fixed" system has a poor transient response at the resonance frequency now, that is the consequence of using a storage mechanism to achieve efficiency.

jn
Two thumbs up !
[fixing a resonance with another resonance]
Similar problems with acoustic 'traps'.

Last edited by RNMarsh; 26th September 2012 at 03:43 PM.
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Old 26th September 2012, 03:41 PM   #1274
SY is offline SY  United States
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Quote:
Originally Posted by gpapag View Post
Would you be satisfied from the result of applying a pre equalized signal to your speakers to compensate for one room acoustic resonance(assume perfect match of fo and Q)?
No, that's not minimum phase and it's also not single-valued.
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Old 26th September 2012, 03:45 PM   #1275
hhoyt is offline hhoyt  United States
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Default Horns

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Originally Posted by jneutron View Post
...I don't like multi-order speakers for that reason. When an energy storage mechanism is used to increase conversion efficiency, transient response suffers...Give me horns anyday...jn
Way off topic, but I have to chime in, that I 100% agree with the multi-order enclosure analysis, (I greatly prefer acoustic suspension myself) but only pure radial horns do not suffer from reflection-induced distortion as proven by Dr. Gene Patronis of GT. I attended his seminars a few years back where each type (tractrix, biradial, exponential, etc.) were demonstrated and the difference is not small, especially as SPL increases and the air becomes non-linear in the throat.

He holds many patents in this field and is worth a read...back to the topic at hand...

Howie

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Old 26th September 2012, 03:50 PM   #1276
RNMarsh is offline RNMarsh  United States
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Default MultiTone tests

The multitone tests most closely simulates a music signal source and produces both Im and harmonics. In checking the available published test data when using such, the 'noise' or grass between the tones grows by 20db when 15 tones are used. Rises another 20db when 30 tones are used (40db rise). I assume this increase in noise/unwanted freqs continues with ever more applied tones. So, we can assume that the level might contribute to the coloration of sound heard if the amplifier (opamp) does not have an extreamly low distortion to begin with. Thx - RNm

Last edited by RNMarsh; 26th September 2012 at 04:11 PM.
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Old 26th September 2012, 03:53 PM   #1277
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Originally Posted by gpapag View Post
For a tip with an effective mass of 0.27mg (Denon DL-103)following a theoretical groove with an 20KHz triangular 5cm/sec modulation, the resulting peak acceleration is 10,000m/sec^2 (1020G).
Is 20 khz triangular realistic? I would have expected sine for this derivation. Are the peak G's representing slew max or where the stylus hits the vinyl wall?

jn
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Old 26th September 2012, 03:55 PM   #1278
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I found one more interesting discrete opamp. Looks like an instrumental amp loaded on output transformer. V/I converters drive controlled by current common cathode stages with deep feedback by voltage. However it is power amp, but can be used as line level output stage with smaller tubes. Thanks to transformer output can be balanced, for professional studio usage.
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Old 26th September 2012, 03:59 PM   #1279
bcarso is offline bcarso  United States
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Originally Posted by scott wurcer View Post
This is very different from a ribbon mic where the "motor" is almost massless and the field huge.
Yes. And iirc you can drive a ribbon microphone to low but audible levels, though you wouldn't want to. Reminds me of the time I drove a tuning fork crystal a little too hard and heard it break.

Speaking of bad news for cartridges, one could put d.c. current through one you weren't too fond of and listen to the changes to the frequency response.
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Old 26th September 2012, 04:00 PM   #1280
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by Wavebourn View Post
I found one more interesting discrete opamp. Looks like an instrumental amp loaded on output transformer. V/I converters drive controlled by current common cathode stages with deep feedback by voltage. However it is power amp, but can be used as line level output stage with smaller tubes. Thanks to transformer output can be balanced, for professional studio usage.
Tie R3, R4 together and change to cascoded jFEts? Change pentodes to low power triodes = line stage.

Last edited by RNMarsh; 26th September 2012 at 04:13 PM.
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