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Omnitronic MM-2 USB measurement mic vs UMIK-1 & UMM-6

Graph Feppar

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I am looking to buy cheap measurement usb microphone in Europe. I found 3 potential candidates, UMIK-1 by miniDSP, UMM-6 by Dayton Audio and MM-2 by Omnitronic. I have never heard about this Omnitronic company before, they appear to be from Germany. Their microphone is by far cheapest, it cost just 54,90€ compared to 99,00€ for UMIK-1 & UMM-6.

Just like the Crosslabs in USA who sell UMIK-1 with individual calibration file, akulap.de sells calibrated UMIK-1 for 122€ and MM2 for 94€. Not only is the MM2 cheaper, its also has much higher maximum spl 133db compared to 105db of UMIK-1. Ofcourse, this makes it much noisier but I am not going to record real life band, I just want to measure frequency response and distortion.
The closer the sound pressure is to the SPL limit of microphone, the more will the microphone distort, that means MM2 is far superior to UMIK for THD measurements, the high noise floor is easily reduced possibly to infinite low value by using sufficiently long averaging. The Dayton UMM-6 max SPL is 127db, a midway between sensitive UMIK-1 and high SPL tolerant MM2.

I have zero experience with any of these measurement microphones, which one is best?

1. Do I need Crosslabs or Akulap calibrated mic or are the factory calibration files accurate enough?
2. Which of these 3 microphones is highest quality/reliablity?
3. Who are these Omnitronics? Is this MM-2 their unique microphone or is this just rebranded mic?
4. What are all significant differences between there 3 microphones?
 

staticV3

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The closer the sound pressure is to the SPL limit of microphone, the more will the microphone distort, that means MM2 is far superior to UMIK for THD measurements
That's the wrong conclusion, especially with USB mics where SPL may be limited by the ADC sensitivity, much earlier than by the mic's THD.

Actual measurements determine which of these is better for THD, not their max SPL.
 
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Graph Feppar

Graph Feppar

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That's the wrong conclusion, especially with USB mics where SPL may be limited by the ADC sensitivity, much earlier than by the mic's THD.

Actual measurements determine which of these is better for THD, not their max SPL.
You are 100% right, still, in theory, higher SPL mic will have less distortion at given SPL vs comparable but lower SPL microphone. I already found this thread from miniDSP forum where user notes that UMIK-1 shows increasing THD the closer it is to the speaker despite speaker being constant volume while higher spl dayton UMM-6 does not show this behaviour, this points to my theoretical expectation being correct atleast in the UMIK-1 vs UMM-6 case.

It is true that the quality of internal electronics like ADC for example can make lower max SPL microphone have equal or lower distortion at given loudness as compared to the higher spl microphone, but considering that these two microphones are in same price range and Daytons spl limit is 22db higher, its no surprise that UMIK-1 thd increases faster.
 
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docjordan

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Hello,

the cheap Omnitronic mic has significant USB Chirping see background of usb chirping

In addition, I created a lot of articles about background of measurment microphone covering low noise , high SPL, USB interfaces and so on
background for measurement microphones

In general all the cheap mics with 1/4" capsule in a 1/2" housing (ECM8000) are ok for room acoustics, reverberation, but not for low noise measurements recording etc.
The frequency response below 5khz is typically ok, anything above has some "variations" ;-)

docjordan
 
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Graph Feppar

Graph Feppar

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Hello,

the cheap Omnitronic mic has significant USB Chirping see background of usb chirping

In addition, I created a lot of articles about background of measurment microphone covering low noise , high SPL, USB interfaces and so on
background for measurement microphones

In general all the cheap mics with 1/4" capsule in a 1/2" housing (ECM8000) are ok for room acoustics, reverberation, but not for low noise measurements recording etc.
The frequency response below 5khz is typically ok, anything above has some "variations" ;-)

docjordan
Hey! Hi! You are the owner of the akulap.de right? I am very happy that you replied to my thread :). I am considering which microphone to buy from you.
I have couple questions.

1. That screenshot of spectrum in the chirping article, thats from the MM-2 usb microphone?
2. How much less chirping does the UMIK-1 have?
3. Why dont you have Dayton Audio UMM-6 in your shop?
4. Did you teardown the MM-2 microphone to look whats inside like you did with UMIK 1 & 2?
5. Can you calibrate Dayton UMM-6 if I send it to you?
 

DVDdoug

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The closer the sound pressure is to the SPL limit of microphone, the more will the microphone distort,
That's not generally true.

A USB mic should have insignificant distortion until the built-in ADC clips at 0dBFS.

With a studio condenser, usually it's the built-in head-amp that clips and some have a "pad" switch to optionally knock-down the signal into the head amp. It may "soft clip" before it hard-clips, or not, but you'd have to get close to its limit electrical limit.

Dynamic mics essentially have no limits. The famous SM57/58 can go over 150dB SPLwhere it's putting out line level and you don't need a preamp! (maybe up over 170dB where the acoustic sound wave hits a full-vacuum on the negative-half of the wave, and the air clips!)
 
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Graph Feppar

Graph Feppar

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That's not generally true.

A USB mic should have insignificant distortion until the built-in ADC clips at 0dBFS.

With a studio condenser, usually it's the built-in head-amp that clips and some have a "pad" switch to optionally knock-down the signal into the head amp. It may "soft clip" before it hard-clips, or not, but you'd have to get close to its limit electrical limit.

Dynamic mics essentially have no limits. The famous SM57/58 can go over 150dB SPLwhere it's putting out line level and you don't need a preamp! (maybe up over 170dB where the acoustic sound wave hits a full-vacuum on the negative-half of the wave, and the air clips!)
That is interesting, do you have any measurements to back up this claim? I have never seen any THD test of cheap usb measurement microphones. I would love to see, UMIK-1, UMM-6 and MM-2 thd measurements with small steps like 1 or 2 db from 90db to 110db.
 

docjordan

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That is interesting, do you have any measurements to back up this claim? I have never seen any THD test of cheap usb measurement microphones. I would love to see, UMIK-1, UMM-6 and MM-2 thd measurements with small steps like 1 or 2 db from 90db to 110db.

Unfortunatly, I do not know of a reliable sound source that can can handle these levels at low distortion. You want to measure the distortion of the mic, not the speaker.
Maybe using a professional IEC61672 1/4" capsule as a electrostatic soundsource in a small cavity.
Typically you measure just the clipping/overload point of a capsule some basic info about high SPL . I can measure high SPL up to 170dB
But this measurment is intended for finding the overload point. The focus is on distortion above 1%

I'm open to create a low distortion measurement setup (maybe others did this). Since I own almost all of the typical measurment mics, I can measure them. But up to now it was not on my focus ;-)

All the cheaper mics with simple electrete 1/4" should be similar from the acoustical overload point. But thye use different DC-bias and different gain stages. Therefore electrical clipping will occur much earlier.


docjordan
 
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docjordan

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Hey! Hi! You are the owner of the akulap.de right? I am very happy that you replied to my thread :). I am considering which microphone to buy from you.
I have couple questions.

1. That screenshot of spectrum in the chirping article, thats from the MM-2 usb microphone?
2. How much less chirping does the UMIK-1 have?
3. Why dont you have Dayton Audio UMM-6 in your shop?
4. Did you teardown the MM-2 microphone to look whats inside like you did with UMIK 1 & 2?
5. Can you calibrate Dayton UMM-6 if I send it to you?

Yes,
I'm the owner of
www.akulap.de
www.dr-jordan-design.de
www.akustik-messen.de

akulap.de serves as a shop for all kind of article related to audio measurements
www.akustik-messen.de has no shop, but on this this site I focus on background information

I cover room-, building- and my personal focus psycho-acoustics. In addition, I offer measurement services, based on my APX555 as the work horse.

That's just for introduction, I'm in the business of audio measurmetns for more than 25years ,-)


To answer the questions above:

1) no, it was a very cheap usb mic for demonstration. The MM-2 is a little better
2) Umik-1 not audible. In this article you find some listening tests with the UMIK-1
A good USB measurment mic is just limited by teh capsule noise. However, 1/4" capsules are quite noisy in general. Therfore it is easy to mask any USB chirps.
3)nobody can offer ALL mics. My fcous is more on professional 1/2" systems.... In teh cheaper pricerange the UMI-1 is the best you can get for your money. And this mic is perfect for room acoustics.
4) Yes I did some photos
mm2_body_cap_1k.jpg



The capsule is not removable like professional mics, you can remove it with force, but typically you damage it

mm2_capsule_cut.jpg


A small and cheap 1/4" capsule in a larger housing.....

mm2_PCB_front.jpg


A single chip controller

mm2_PCB_back_cut.jpg


A cheap and simple solution


5. Can you calibrate Dayton UMM-6 if I send it to you?
Yes, I can do it in my precision pressure chamber (no free-field)

docjordan
 

docjordan

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all these simple measurment mics, use capsules with a typical sensitiviy of 12mV/Pa
with an SPL of 133dB RMS you get an input voltage of around 1V RMS. Typically, the (internal) FET starts clipping much earlier. There are some mods to improve this

docjordan
 

docjordan

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Here are calibrated selfnoise measurments from an MM2.
The microphone was acoustically shielded

1/3 octave measurment

mm2usb_mix100_self_noise.png


and the FFT

mm2usb_mix100_self_noise_fft.png


Chirping is clearly visible and audible.

But you still can do good room acoustics measurements with it.
 
OP
Graph Feppar

Graph Feppar

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Unfortunatly, I do not know of a reliable sound source that can can handle these levels at low distortion. You want to measure the distortion of the mic, not the speaker.
I have an idea! Speakers & subwoofers THD performance varies greatly depending on model, frequency and volume, but there is almost univeral rule that applies to everything except balanced armature IEM drivers and that rule is that the lower the driver excursion, the lower the distortion. This means that in theory even cheap dynamic driver could achieve ultra low THD if its set to sufficiently low volume.

Where I am going with this? Take any half decent ported speaker or subwoofer, wrap the microphone in towel or something such that the capsule remains exposed and put this inside the bass port as sort of plug. This way you can apply large pressure on the microphone under test without the driver having to reach into non-linear excursion levels. Another variant of this is 3D printing a funnel, a sort of reverse horn, that would form a tube/tunnel between the driver and the microphone capsule, this too will amplify the pressure at the capsule relative to driver excursion.
 

docjordan

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I have an idea! Speakers & subwoofers THD performance varies greatly depending on model, frequency and volume, but there is almost univeral rule that applies to everything except balanced armature IEM drivers and that rule is that the lower the driver excursion, the lower the distortion. This means that in theory even cheap dynamic driver could achieve ultra low THD if its set to sufficiently low volume.

Where I am going with this? Take any half decent ported speaker or subwoofer, wrap the microphone in towel or something such that the capsule remains exposed and put this inside the bass port as sort of plug. This way you can apply large pressure on the microphone under test without the driver having to reach into non-linear excursion levels. Another variant of this is 3D printing a funnel, a sort of reverse horn, that would form a tube/tunnel between the driver and the microphone capsule, this too will amplify the pressure at the capsule relative to driver excursion.

Currently I'm using something similar. a 2" high power pressure driver with a 3D printed chamber.

My refernce mic is a 1/4" MK301E from Microtech Gefell

high_SPL_setup.jpg



A sweep level vs. SPL

high_SPL_setup_THD.jpg


At present I focussed on maximum SPL with THD <3%. But, if have time I'll carefully analyse the low and very low THD range.
 

docjordan

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There exist some more sophisticated techniques for high SPL up to 180dB :)
With coupled tubes

for details https://www.researchgate.net/public...URE_SOURCE_AT_1KHZ_BY_RESONANT_COUPLING_TUBES

It is based on the approch from Oberst back in 1940

commercial products exist from Bruel&Kjaer and a clone from BWSA

Allthough I do not need such high sound pressure level in this range in my daily work,
it is still interesting, because with resonant effect you get lower distortion from the speaker driver

docjordan
 

ZolaIII

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For simplicity of use and calibration that works with REW so that you also use it as SPL meter buy UMIK-1. They will all be good to 5 KHz or a bit more (probably 7 KHz) under 45° vertically. Even with UMIK-1 it's still recommend that you use 45° with appropriate cal file (tho cal file has correction for it and above in all angles cal files still to make it as accurate as high as possible). You won't be measuring SPL directly on site of nuclear blast.
 
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Graph Feppar

Graph Feppar

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For simplicity of use and calibration that works with REW so that you also use it as SPL meter buy UMIK-1. They will all be good to 5 KHz or a bit more (probably 7 KHz) under 45° vertically. Even with UMIK-1 it's still recommend that you use 45° with appropriate cal file (tho cal file has correction for it and above in all angles cal files still to make it as accurate as high as possible). You won't be measuring SPL directly on site of nuclear blast.
Omnitronic MM-2 and Dayton UMM-6 cant work as SPL meters out of the box with REW?
 

ZolaIII

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Omnitronic MM-2 and Dayton UMM-6 cant work as SPL meters out of the box with REW?
As much as I know not, you need stand alone one (apps aren't really accurate) to enter SPL level and calibrate that part. After that of course they can be used as SPL meter RTA and cetera. Cal file is for alignment of measured deviations from 0 dB at given frequency (EQ for microphone) accessible by serial number. Again pretty much any measurement microphone is good enough up to
5~7 KHz. It's not that you don't want to correct highs, just not by PEQ but with FIR filter.
 

docjordan

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To make reliable SPL measurements (not relative frequency response or RT60) you will typically need a sound level calibrator. Some background
Most USB mics have a HW mixer device (gain). When you change the gain, the SPL reading will change.
Without an absolute reference level, a SPL measurement won't work.
Some measurment apps include a calibration factor and can adjust the HW mixer. They work out of the box with a usb measurement mic.

UMIK-1: unfortunatly it has a strange diameter and does not fit to a normal calibrator. you will need an adapter. Again: just for absolute sound level measurments.
 

staticV3

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UMIK-1 is advantageous in that being a UAC1 device, it has no HW volume control capabilities.

When used with the ASIO or Wasapi Shared API, its dBFS/dB SPL is fixed, with no way to adjust.

That means that combined with miniDSP's cal file which includes both FR compensation and SPL calibration, you have a relatively reliable SPL meter, as long as you use ASIO or Wasapi Shared.

Naturally, this does not protect from sensitivity drift, so a proper manual recalibration is definitely recommended for applications where accurate SPL is desired, especially if the UMIK-1 was purchased a while ago.
 

docjordan

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Yes, this true and very helpful for the UMIk-1. No mixer HW. You can adjust the gain with some DIP switches on the PCB. But then you not calibrated anymore.

The MM2 has a mixer HW, and this is more confusing rather than useful. It makes calibration dificult

Therefore the UMIk1 is a very cool device for the money
 
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