Improving measurements with a new mic

Fon

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Hello,

Currently I´m using the Umik-1 USB mic to do the measurements in Audiolense. I´m wondering if a mic like the Earthworks M23 or the Audix TM-1 will be better for that (mostly time alignment). My DAC is the Okto dac8 PRO, it has a micrphone input (AES/EBU) but doesn´t provide phantom power.

Thank you
 

hulkss

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Yes, there can be considerable difference. A cheap mic is not built to be consistent in performance over time or with changes in humidity or temperature. You also want flat phase and frequency response.
I use an Earthworks M30.

It has a small diameter measurement tip that greatly improves the omnidirectional performance for measurement of multichannel systems and room response. The response corrections in the calibration file needed by cheaper microphones are only valid in one direction from the mic.
 

dsnyder0cnn

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I found that purchasing a mic calibrated by Cross•Spectrum Labs improved my results with Dirac Live vs using the cheap mic that came with my HT processor. The calibration files they provide include corrections for 0º, 45º, and 90º orientation. I don't know how much measurements will drift over time or the degree to which results are affected by temperature and humidity, but they do provide the conditions under which the calibration files were created:

46822


The calibration files seem to be more accurate than the ones provided by miniDP and Dayton Audio, so I think it's worth the modest extra expense to purchase from Cross•Spectrum Labs. Only downside is limited availability and extra time, but I've found it to be worth the wait. I've purchased both an EMM-6 and UMIK-2 from them. Results are consistent between the two, so I'm happy.

My thinking is that deviations of a dB or two vs. what I might achieve with a nicer mic are insignificant to my application–measuring the vagaries of loudspeaker + room response.
 
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hulkss

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The graph above reveals another issue with cheaper mics - calibrating below 30 Hz. You need a good mic to not need huge amounts of correction plus a very good mic preamp with flat response at low frequencies. I like to correct down to 16 Hz which is the lowest musical frequency (two pipe organs exist that go to 8 Hz). Below 16 Hz is pretty much just special effects as you can only feel it, not hear it. My IB subs play well below 16 Hz but I don't apply correction filters there.
 

dsnyder0cnn

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The graph above reveals another issue with cheaper mics - calibrating below 30 Hz. You need a good mic to not need huge amounts of correction plus a very good mic preamp with flat response at low frequencies. I like to correct down to 16 Hz which is the lowest musical frequency (two pipe organs exist that go to 8 Hz). Below 16 Hz is pretty much just special effects as you can only feel it, not hear it. My IB subs play well below 16 Hz but I don't apply correction filters there.
I don't disagree, but this mic requires less than 3 dB of correction at 20 Hz, which is good enough for me. If can tune a system to have perceptually flat response from 27 Hz to 17 kHz, -3 dB at a little over 20 Hz, I'm pretty happy. But yes, horses for courses…if your requirements are greater, your tools need to be greater too.
 

G29

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Hello,

Currently I´m using the Umik-1 USB mic to do the measurements in Audiolense. I´m wondering if a mic like the Earthworks M23 or the Audix TM-1 will be better for that (mostly time alignment). My DAC is the Okto dac8 PRO, it has a micrphone input (AES/EBU) but doesn´t provide phantom power.

Thank you
Your DAC8 PRO 8-channel DAC does NOT have an analog mic input.

This was one of the requested options made to OKTO Research (to prevent having separarte ADC and DAC clocks sync issues) when they were in their requirements gathering stage and it was not implemented.
 
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Fon

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Your DAC8 PRO 8-channel DAC does NOT have an analog mic input.

This was one of the requested options made to OKTO Research (to prevent having separarte ADC and DAC clocks sync issues) when they were in their requirements gathering stage and it was not implemented.
You´re right, only digital no analog.

How can we know if there are clock sync issues using a USB mic? I normaly take several measurements in the same spot and compare the timing results, I think they are consistent, with a maximum deviation of 0.02 ms between them.
 

Fon

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I don't disagree, but this mic requires less than 3 dB of correction at 20 Hz, which is good enough for me. If can tune a system to have perceptually flat response from 27 Hz to 17 kHz, -3 dB at a little over 20 Hz, I'm pretty happy. But yes, horses for courses…if your requirements are greater, your tools need to be greater too.
Mine is from Cross-Spectum too.
 

dsnyder0cnn

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IMO, a calibrated measurement microphone will get the job done. But the calibration needs to be properly done. And of course these microphones are fragile and can be damaged.
Yes. Have you had any good or bad experiences with Cross•Spectrum Labs? I treat my mics carefully, keeping them in their cases with silica jell pack to keep the capsules dry. But I do wonder how often I need to send them back for recalibration. I just got a UMIK-2 in from them (fresh), so I guess I can pull both out and see if there's more than a dB or two of drift.
 

DanDan

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It seems intuitive, perhaps logical, that a great mic with Lab perfect polar and phase and FR responses would deliver better information the the analysing algorithms of Dirac etc. Surely this should deliver better choices, better filters?
 

hulkss

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Yes, mics have greater errors than most things audiophiles fret over.
 

DanDan

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Hi Mitchco...... I have had my eye on isemcon for a long time..... have you experienced them? I like the notion of the new Neumann MA1 Mic. I am blessed to have a few DPA 4060/1 mics. These are tiny and become very very flat when the HF boosting grille is popped off. I used to use the mic on a B&K 2250 for my finest measurement and Dirac/Sonarworks jobs. Lately I have moved on to an NTI meter which has a detachable phantom powered mic of apparently the very highest quality. M2230.
 

Mitchco

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Hi DanDan, yes, I have been using isemcon mics for 10 years. Good company and mics. The DPA 4060's are very nice for sure. I have not seen the M2230 before, good specs!
 

dsnyder0cnn

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Here is the polar response for an M30. Very good at picking up loudspeakers and the room sound reflections from all directions.

View attachment 46843
Here's the polar response of my EMM-6, as measured by Cross•Spectrum Labs. I'm not saying that it's equivalent, but the differences seem to be smaller than the difference in price would suggest. Note, this is a measurement of my specific mic. Results may vary from unit to unit.

47283
 

Omid

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If anyone has both expensive and cheaper calibrated microphones like the EMM6 and has time to do an REW Sweep of their speakers with both microphones and superimpose them on the same graph it will show us how much of a difference there is, and whether it’s worthwhile spending more on a better microphone for our Audiolense measurements.
 

Omid

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It looks like someone has already done this here:
It looks like there are small differences between Behringer and earthworks in very high-pitched tones.
Other considerations are phase, ringing, and how fast various microphones’ calibration is valid for (Maybe a cheap microphone will go out of calibration faster?).
 

hulkss

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Your digital filter corrections are only as good as the measurement they are based on. Both magnitude and phase.
 

juicehifi

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Comparing raw frequency responses as seem to be what has been done when I follow the link above is pretty useless, imo. A proper evaluation has to include the calibration file. And that in-room measurement comparisons are not fit to evaluate in any case.

I used to sell Isemcon mics, btw. Very serious guy behind the microphones. And I trust their calibration as well as the end result.

So any measurement mic which has been properly calibrated is up there, IMO.
 

2234rew

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Hi @Mitchco

I had 2 different UMIK-2's both result in shocking corrections - end result sounded like serious phase issues.

Same issue in 2 different systems, with 2 different UMIK-2's.

Compared to UMIK-1 I wonder if the smaller capsule of UMIK-2 makes it less good for room correction measurements.

Maybe UMIK-2 better for nearfield speaker measurements.

I then used an Earthworks M23 and order was restored - couldn't be happier with the results.

Note I'm not talking about the Cross Spectrum Labs UMIK-2 - maybe that is better than the stock miniDSP one. I can't comment.

I wasted so many weekends with bad results with UMIK-2, trying to figure why. M23 measurement resulted in beautiful sounding room correction on the very first measurement attempt :)
 

dsnyder0cnn

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Hi @Mitchco

I had 2 different UMIK-2's both result in shocking corrections - end result sounded like serious phase issues.

Same issue in 2 different systems, with 2 different UMIK-2's.

Compared to UMIK-1 I wonder if the smaller capsule of UMIK-2 makes it less good for room correction measurements.

Maybe UMIK-2 better for nearfield speaker measurements.

I then used an Earthworks M23 and order was restored - couldn't be happier with the results.

Note I'm not talking about the Cross Spectrum Labs UMIK-2 - maybe that is better than the stock miniDSP one. I can't comment.

I wasted so many weekends with bad results with UMIK-2, trying to figure why. M23 measurement resulted in beautiful sounding room correction on the very first measurement attempt :)
This thread has got me wondering if I should up my game with an Earthworks mic.

I've been meaning to compare measurements between my UMIK-2 and EMM-6. I purchased both from Cross•Spectrum Labs with their best calibration. I would expect them to be within a dB or so of each other, but it will be interesting to see. I also have off-the-shelf Dayton Audio UMM-6 and iMM-6 mics with calibration files from Parts Express. I may compare these too while I'm at it to see how far off they are.

Mitch has pointed out that timing response can be a little off when using a USB mic because there's no single clock reference. Perhaps that's the source of the phase issues you encountered?
 

Mitchco

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There are two separate issues when talking measurement microphones. Was the mic properly calibrated? And if using a USB mic, potential timing issues.

I made a comparison a while back between analog and USB mic. And in the case of the USB mic, one with and without Audiolense's "clock drift correction" using my triamp system and Lynx Hilo.

Analog mic:
Analog mic.jpg

USB mic with clock drift correction:
UMIK1 USB with clock drift correction.jpg

USB mic without clock drift correction:
UMIK1 USB without clock drift correction.jpg


Bernt's clock drift correction works very well.

There are (very) small differences in the timing between the analog mic and USB with clock drift correction. There are also frequency response differences at the extremes between all three measurements.

The analog mic shows a perfect channel match in the low frequencies and natural rolloff in the top octave. Whereas the USB mic shows a bit of low frequency mismatch between channels and a bit of a rising top end. Now whether any of that is audible...

Of course, the USB mic measurement without clock drift correction is unusable timing wise.

While the USB mic is "convenient" I sold mine and stuck with the isecmcon analog mic.
 
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