• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Microphone Distortion Higher than Speakers? Yes? No? Maybe?

Did I conduct my test correctly to reveal microphone distortion?

  • Yes

    Votes: 4 23.5%
  • No

    Votes: 5 29.4%
  • Maybe

    Votes: 2 11.8%
  • Clean your bedroom

    Votes: 7 41.2%

  • Total voters
    17

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
I would like to share my YouTube video where I evaluate my microphone's distortion (Dayton UMM6). What do you think about my conclusions? Yes? No? Maybe?


I adopted my test procedure from here.

This question arose from my own curiosity since none of my IMD tests for speakers do any better than -65dB. This led me to suspect my measurements system was not capable of measuring better than this level.

I look forward to investigating other test microphones so that I can further explore the distortion in loudspeakers as a topic.
 

MRC01

Major Contributor
Joined
Feb 5, 2019
Messages
3,424
Likes
4,030
Location
Pacific Northwest
The method is either incorrect, or I don't understand it.
First you played single tones at 60 Hz and 1300 Hz, respectively.
Then you played both tones simultaneously, and intermodulation products appeared in the results.

You conclude that the intermodulation came from the mic, but how do you arrive at that conclusion? It seems likely that the speaker created the intermodulation tones. You didn't see them with the single tones simply because you didn't play both tones simultaneously - single tones can't create intermodulation.
 

MRC01

Major Contributor
Joined
Feb 5, 2019
Messages
3,424
Likes
4,030
Location
Pacific Northwest
Note: I have shown in my system that my speakers have lower distortion than the UMIK-1 measuring mic. When I measure distortion using Rode NT-1A mics, I get lower measured distortion than I get when using the UMIK-1. That's with all else equal: mic position, system volume / loudness, etc. Repeatable and consistent.
 

alex-z

Addicted to Fun and Learning
Joined
Feb 19, 2021
Messages
910
Likes
1,684
Location
Canada
Just commented the same on the video, but I think it is just a product of the capsule size. The UMM6 is only 1/4", and you are measuring 100dB, which is quite significant.

Technically the mic may be rated for 135dB 1%, but that is for 1000Hz, and only THD. I see similar issues as to your video with a UMIK-1, and my only real solution is measuring outdoors at 2 metres to reduce SPL at the capsule.
 

MakeMineVinyl

Major Contributor
Joined
Jun 5, 2020
Messages
3,558
Likes
5,871
Location
Santa Fe, NM
Different microphones, like different speakers, will perform differently in regards to distortion. They're electro-mechanical devices after all. I wouldn't expect the UMIK-1 to be the equal to an expensive Bruel & Kjaer for instance.
 
OP
J

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
The method is either incorrect, or I don't understand it.
First you played single tones at 60 Hz and 1300 Hz, respectively.
Then you played both tones simultaneously, and intermodulation products appeared in the results.

You conclude that the intermodulation came from the mic, but how do you arrive at that conclusion? It seems likely that the speaker created the intermodulation tones. You didn't see them with the single tones simply because you didn't play both tones simultaneously - single tones can't create intermodulation.
My conclusion that it is from my mic only is not my own. It's a clever method that I adopted and it is well documented in various publications. Below is the excerpt from the link I provided in my original post.

"The purpose of this sequence is to measure the Intermodulation Distortion (IM) of a microphone. Unlike traditional IM distortion measurements performed on loudspeakers, this technique requires the test stimulus to be played through two separate source loudspeakers, one for the playback of the Master (fixed) tone and one for the playback of the Slave (sweep) tone. If a single source loudspeaker were employed, it would generate its own IM products which would be impossible to separate from that of the microphone under test. The sequence’s default stimulus parameters are a 100 Hz tone (Master) and a stepped sine sweep from 10 kHz to 224 Hz (Slave). Stimulus levels should be set to maintain a 4:1 ratio of Master to Slave. Sequence defaults are 94 dBSPL (Slave) and 106 dBSPL (Master)."
 
OP
J

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
Just commented the same on the video, but I think it is just a product of the capsule size. The UMM6 is only 1/4", and you are measuring 100dB, which is quite significant.

Technically the mic may be rated for 135dB 1%, but that is for 1000Hz, and only THD. I see similar issues as to your video with a UMIK-1, and my only real solution is measuring outdoors at 2 metres to reduce SPL at the capsule.
The concern which led me to do the test is that I've never measured IMD multitone better than -65dB. This is regardless of SPL level, indoor or outdoor. So in the context of investigating loudspeaker linearity, I suspect I need a better microphone.
 
OP
J

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
Different microphones, like different speakers, will perform differently in regards to distortion. They're electro-mechanical devices after all. I wouldn't expect the UMIK-1 to be the equal to an expensive Bruel & Kjaer for instance.
Apparently so. Although, wouldn't you agree that it's commonly understood from most that microphone distortion is far lower than any loudspeaker? I only mention it because often one dismisses concerns based on common perception. That is why it has taken me so long to measure the microphone!
 

Robin L

Master Contributor
Joined
Sep 2, 2019
Messages
5,211
Likes
7,589
Location
1 mile east of Sleater Kinney Rd
The concern which led me to do the test is that I've never measured IMD multitone better than -65dB. This is regardless of SPL level, indoor or outdoor. So in the context of investigating loudspeaker linearity, I suspect I need a better microphone.
I don't think so. Of all the transducers, speakers [having the greatest moving mass, and thus inertia] will always have higher levels of distortion than microphones. -65 db = 0.05% THD. Speakers are lucky to reach 0.5% THD, or -46 db. I don't think your measurements are lying.
 
OP
J

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
I don't think so. Of all the transducers, speakers [having the greatest moving mass, and thus inertia] will always have higher levels of distortion than microphones. -65 db = 0.05% THD. Speakers are lucky to reach 0.5% THD, or -46 db. I don't think your measurements are lying.
That's not been my experience. Even with difficult multitone tests a compression driver can do -65dB. But I've never been able to better this figure which is why I've done this test. To add to this, certain drivers sound better than others even though they both measure at -65dB, this suggests there could be more insight on driver performance if we could see lower into the noise floor of the driver.
 

MakeMineVinyl

Major Contributor
Joined
Jun 5, 2020
Messages
3,558
Likes
5,871
Location
Santa Fe, NM
Apparently so. Although, wouldn't you agree that it's commonly understood from most that microphone distortion is far lower than any loudspeaker? I only mention it because often one dismisses concerns based on common perception. That is why it has taken me so long to measure the microphone!
Microphone distortion is generally lower than some speakers, but when speakers get <= 0.1% distortion, it can be a tossup whether a microphone is lower or not, and of course it depends on what frequencies you're comparing.
 

mtg90

Member
Joined
May 24, 2021
Messages
53
Likes
127
Location
Illinois
I started noticing weird distortion results with my UMIK-1 when trying to compare distortion from compression drivers a while back, realized the mic was heavily distorting on the 2nd harmonic (~0.5% @ 100dB, ~1% @ 110 dB) and masking the distortion from the drivers. I ended up with an Earthworks M23 to solve the harmonic distortion issues I was seeing in those measurements.

Here are some of the tests and comparisons I posted where I moved the mic while the driver output remained constant. This way the distortion from the driver is constant but you can see the distortion from the mic changes as the SPL at the capsule increased where it should remain constant if it wasn't distorting itself, or it should fall as the SNR increases at those higher input levels. This was not the case for most mics tested:

I just realized I really need to clean up the text in the distortion portion to make it more clear how things are being tested and what the input levels are.
 

formula 977

Active Member
Joined
Apr 8, 2022
Messages
105
Likes
88
I was just thinking about the mic performance of the Klippel system overall but mostly relating to IMD. I am all for what you propose. Listening to a complex musical passage as part of a single recording and being less than impressed with a collapse in resolution, IMD would be a good place to start as an attempt to correlate the hearing with the measuring. An Interesting thread.
 

MRC01

Major Contributor
Joined
Feb 5, 2019
Messages
3,424
Likes
4,030
Location
Pacific Northwest
... Unlike traditional IM distortion measurements performed on loudspeakers, this technique requires the test stimulus to be played through two separate source loudspeakers, one for the playback of the Master (fixed) tone and one for the playback of the Slave (sweep) tone. ...
I see, each tone produced by a different speaker. That sounds legit.
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,314
Location
UK
 
OP
J

Joseph Crowe

Active Member
Joined
Oct 25, 2019
Messages
105
Likes
260
In room distortion measurements are not accurate anyhow.
Really? That’s not been my experience. There’s virtually no difference between indoor and outdoor assuming both environments are quiet and the mic is relatively close to the driver.
 

MakeMineVinyl

Major Contributor
Joined
Jun 5, 2020
Messages
3,558
Likes
5,871
Location
Santa Fe, NM
I compared my Bruel & Kjaer instrumentation 1/2" microphone (very costly) to the MiniDSP UMK-1. Here are the frequency responses of my left channel speaker at the listening position (11' away) overlaid. Note that I measured using the B&K mic (no cal file) at both 0 degrees and 90 degrees incidence and the UMK-1 was at 90 degrees, using the appropriate cal file. As expected, the 0 degrees measurement with the B&K microphone had a buildup in the high frequencies.

I turned off my subwoofers for these measurements.

FR.jpg
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,523
Likes
37,056
I compared my Bruel & Kjaer 1/2" microphone (very costly) to the MiniDSP UMK-1. Here are the frequency responses of my left channel speaker at the listening position (11' away) overlaid. Note that I measured using the B&K mic (no cal file) at both 0 degrees and 90 degrees incidence and the UMK-1 was at 90 degrees, using the appropriate cal file. As expected, the 0 degrees measurement with the B&K microphone had a buildup in the high frequencies.

I turned off my subwoofers for these measurements.

View attachment 205028
Show us the distortion plot just for grins.
 

Blumlein 88

Grand Contributor
Forum Donor
Joined
Feb 23, 2016
Messages
20,523
Likes
37,056
The method isn't wrong. Plenty of papers describing this. Some even use two tweeters one producing 18 khz and one producing 19 khz.
I would question the use of the tube amp for one of the signals in this case and the large distance between the higher tone and the microphone position.

As for no room measures of distortion being any good that depends. Usually won't be in lower frequencies say 100 hz and lower.

I've done sweeps and single tones using REW for a fair number of microphones. Most appear to have distortion below the speaker I was using. Some didn't. One with quite a bit of distortion was the Audio Technica AT4033. I had three of different vintages and they gave identical results. They were showing considerable distortion at SPLs of 90 db and up. Like a few percent. Probably why they have a bright sound even beyond their FR. You can flatten with EQ and the sound is still rather biting and bright.
 
Top Bottom