John Curl's Blowtorch preamplifier part III

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I have decided to try a big 1" condenser microphone for the 13+14kHz tweeter test and it seems to be the right choice. The 1kHz difference tone has gone and 2 driver test is clean now. And, dynamic range is higher - lower noise.

That is an excellent result.

Is it possible that dynamic microphones will always produce the difference because of the structure of the magnetic circuit?

Jn
 
I am no discoverer :D. There will be more sources of distortion in the dynamic microphone. Large diaphragm condenser microphone has the advantage of light membrane, lower excursion and predictable behavior according to

https://pdfs.semanticscholar.org/e9f8/5980d82b1d8f9bcc2574e38f0c1ef162d07d.pdf
I hardly believe such a distortion exists in a non damaged dynamic mic.
They are largely used in recording studios and live concerts, specially with high SPL sources, like drums, electric guitars etc.
 
I hardly believe such a distortion exists in a non damaged dynamic mic.
They are largely used in recording studios and live concerts, specially with high SPL sources, like drums, electric guitars etc.

So far, 100% of the dynamic mics tested so far with the 13 khz and 14 Khz signals provided by two independent sources has displayed a difference signal 53 dB below the two primary signals.

So far, 100% of the condenser mics tested have displayed zero difference content.

Given the sample size (one each), is it a design function, or is it a compromised device?

jn
 
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PMA, what models of mics are you using? As you surely know, many mics, both dynamic and condenser, have internal transformers (!), which seems to negate trying to determine distortion caused by the magnetic circuit of a speaker being recorded through them. Even that article mentions a tube-transformer path - the transformer makes for an easy balanced output for a tube buffer in a condenser mic.
I hardly believe such a distortion exists in a non damaged dynamic mic.
They are largely used in recording studios and live concerts, specially with high SPL sources, like drums, electric guitars etc.
Dynamic mics such as the model I link to below are indeed very commonly used in such applications. That doesn't mean they don't have distortion or are very low distortion.
> drums, electric guitars etc

Are not very refined sources .
Hard to separate any distorsion .
A lot of studio people can tell what model microphone was used on a recording just by listening. Microphone selection for pop music recording is part of shaping the sound, and not necessarily for lack of distortion. A two-mic stereo technique for recording an orchestra might be different.

Here's 'the standard dynamic microphone' for instruments (but also sometimes used for singers) - many or most "home studios" have one of these, and big studios have at least four (they're inexpensive for "professional mics"). Its most common use is for snare drums and electric guitar amps, but it's also used for lots of other things. The President uses two, because the model has been around a while and the Secret Service is very familiar with it. Check out that device in the middle of the schematic at "Internal Connections."
Shure Publications | User Guides | SM57
 
So far, 100% of the dynamic mics tested so far with the 13 khz and 14 Khz signals provided by two independent sources as displayed a difference signal 53 dB below the two primary signals.

So far, 100% of the condenser mics tested have displayed zero difference content.
Is-it not normal that a 13 and 14Khz together generate a 1KHz beat ?
Well, I believe it is AM.
So, my question is: What was measured and how ? A measurement artifact ? And why this difference between condensers and dynamic ? And what for a ribbon mike ?
 
A lot of studio people can tell what model microphone was used on a recording just by listening. Microphone selection for pop music recording is part of shaping the sound, and not necessarily for lack of distortion. A two-mic stereo technique for recording an orchestra might be different.

Shure Publications | User Guides | SM57
Yes for the first part. I often used dynamic microphones for "ORTF" couple stereo miking. My favorite, during decades, when it was not condensers, were AKG D202 because their more constant directivity (double capsule) or Sennheiser MD 441 (hypercardiod with horn) ... and a lot more.

For the SM57 and 58, those junk mikes from Shure were mostly appreciated by musicians on stage, because the were rugged (when they dont broke in two parts ;-), can work very close to the mouth for singers, not very prone to larsen. And I will not be surprised by a high distortion ;-)
No way to use a condenser mike for singer's voice on stage: Too sensible to "Pops", humidity, larsen, too fragile and... expensive ;-)
 
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Is-it not normal that a 13 and 14Khz together generate a 1KHz beat ?
Well, I believe it is AM.
So, my question is: What was measured and how ? A measurement artifact ? And why this difference between condensers and dynamic ? And what for a ribbon mike ?
PMA's plot of the condenser did not show any energy at 1Khz, but using the same sounds, the dynamic did.

jn
 
JN, if you speak about my measurements, both microphones were condenser types. The ECM8000 had H2 distortion by the difference tone about -68dB, the big 1" microphone did not have a trace of distortion neither H2 nor H3. Noise floor at difference tone for the 1" microphone was about -83dB at 1kHz (1kHz) and about -105dB at 12kHz and 15kHz (H3), dB referred to test signal amplitude. So we may say that distortion of the 1" microphone was for sure <0.01% H2 and <0.001% H3, though we do not know the exact value.

benb: none of the microphones used has a transformer.

P.S.: the problem with microphone specs is that they often define SPL for distortion of 0.5%. However, my 1" specs say it has 0.05% at 1kHz 140dB SPL, which seems to me overoptimistic.
 
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Not all microphone designs use humbucking coil setups, and I am not sure even when they do they would be effective at 15 KHz.

Try with a non-magnetic baffle in front of the mic? Also have you ever seen anything but omni condenser capsules used as primary references? Throwing patterned mics into the mix here means treating the rear wave (they are not pure pressure mics) this adds to confusion.
 
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