Calibration Microphone

[Blumlein 88]

What do you disagree with?

Maybe an over-reaction on my part. What is there is okay, I disagree strongly with dissing USB microphones. When I've suggested it is worthwhile to get an XLR interface it ends up confusing most people. XLR cabling, how to use an interface etc etc. Plus it costs two or three times a USB microphone. So many more people will pay for a USB microphone and manage to use it with little difficulty. The benefits to someone vs not doing anything are quite large. If someone is a do it yourself speaker builder, then yes I'd suggest getting XLR interfaces. Otherwise, there is not all that much you cannot do with a USB microphone for home listener purposes.

 

[MAB]

What do you disagree with?

In context of OP, they wish to make in-room measurements. USB mics are incredibly useful and accurate for in-room measurements. And even cheap USB mics with cal files are calibrated for SPL, which is an incredibly useful in-room measurement. Using a tweeter as an acoustic timing reference is actually really straightforward, so I completely disagree with his characterization that is is 'unnecessarily difficult'. He actually shows just how easy it is to implement an acoustic timing reference... Bravo! And he does nicely demonstrate why a timing reference is important for speaker design. But OP isn't designing speakers. And if OP decides to design speakers in the future, this video shows how easy it is to actually implement a timing reference.

He also shows how close a result he can get across different mics. And his attribution that the difference between the two Earthworks mics is due to age is complete speculation, he never even bothered to compare the factory calibration files to see if they actually measure differently when new! Maybe since he bought it just to return it he never bothered to register it and get the cal file from Earthworks. And the differences between the two M23 are minute, not noteworthy, and specious without the cal files. But none of this is important to the OP's question, what mic to make in-room speaker measurements with?

The UMIK-1 is $110, other good measurement mics even cheaper. An Earthworks mic plus interface will set you back ~$700, even more if you fall into the upgrade trap and go top of the line... With that outlay, you get slightly more convenient timing reference implementation, better distortion and noise measurements, increased accuracy above 10kHz but will also measure all of your LED lights and other sources of noise. All this to end up with nearly identical in-room measurements isn't worth it for most people.

 

[Blumlein 88]

He also shows how close a result he can get across different mics. And his attribution that the difference between the two Earthworks mics is due to age is complete speculation, he never even bothered to compare the factory calibration files to see if they actually measure differently when new! Maybe since he bought it just to return it he never bothered to register it and get the cal file from Earthworks. And the differences between the two M23 are minute, not noteworthy, and specious without the cal files. But none of this is important to the OP's question, what mic to make in-room speaker measurements with?

Looking at his results when I've seen low end discrepancies like he shows it is from some distant not noticed source. Like a delivery truck or some HVAC running next door or a lawnmower down the street. The high frequency differences could be the microphone or he didn't get them in exactly the right position. An error of 1/8th of an inch would cause that much difference.

 

[dfiler]

What do you disagree with?

I’d go with poorly reasoned rather than wrong. The video comes across as broad criticism of usb calibration mics. With more self awareness, I think the point would have been much more narrowly focused. He’s analyzing specialized and relatively rare usage scenarios as if they were the norm.

Basically, for EQ calibration and REW usage, most of the points aren’t applicable. This thread isn’t about near field analysis of multiway speakers with timing complexities. Etc. for room calibration as described by the OP, a usb mic is fine and won’t be limiting in any way.

 

[MAB]

Looking at his results when I've seen low end discrepancies like he shows it is from some distant not noticed source. Like a delivery truck or some HVAC running next door or a lawnmower down the street. The high frequency differences could be the microphone or he didn't get them in exactly the right position. An error of 1/8th of an inch would cause that much difference.

Yes, completely agreed. I think he got his attributions wrong on the FR differences between mics, especially new vs. old M23. He is arguing about things below normal noise and setup differences, as if they are critical. He kind of proves the opposite point he is trying to make, that for anybody making in-room measurements a decent USB mic + calibration is fantastically useful exactly what is needed need for measuring speakers in a room.

 

[alin_im]

Hi all,

coming back to the newbie land...

The Dayton emm-6 has 1 calibration file, i suspect that is done at 0 degrees orientation (horizontal position).

Is that fine for room measurements? i have seen people pointing the microphone 90 degrees (vertical) when doing these type of measurements, but I do not have a 90 calibration file. Are there any drawbacks on using the mic at 0 degrees for room measurements?

I have contacted Dayton, but no response yet. I would assume that if they had a 90 calibration file, they would provide it from the beginning.

 

[Blumlein 88]

This is part guesswork. The size and appearance of the Dayton and Umik are nearly the same. Including the slots around the microphone capsule. You probably would be able to use the 90 degree adjustment from a Umik cal file on the Dayton. Would it be perfect? Probably not. Would it be largely in the right direction? I think so.

What Umik does is make a blanket adjustment for 90 degrees based upon the size of the capsule. You can make the same adjustment for the file you get for the Dayton.

OTOH, you could buy a Dayton from Cross Spectrum labs. They do a superior calibration of your microphone and provide cal files for 0, 45 and 90 degrees.

Cross·Spectrum - Calibrated Dayton Audio EMM-6 Microphones for Sale

Purchase calibrated Dayton Audio EMM-6 measurement microphones, low-cost option for performing precise and accurate sound measurements

www.cross-spectrum.com

 

[alin_im]

This is part guesswork. The size and appearance of the Dayton and Umik are nearly the same. Including the slots around the microphone capsule. You probably would be able to use the 90 degree adjustment from a Umik cal file on the Dayton. Would it be perfect? Probably not. Would it be largely in the right direction? I think so.

What Umik does is make a blanket adjustment for 90 degrees based upon the size of the capsule. You can make the same adjustment for the file you get for the Dayton.

OTOH, you could buy a Dayton from Cross Spectrum labs. They do a superior calibration of your microphone and provide cal files for 0, 45 and 90 degrees.

Cross·Spectrum - Calibrated Dayton Audio EMM-6 Microphones for Sale

Purchase calibrated Dayton Audio EMM-6 measurement microphones, low-cost option for performing precise and accurate sound measurements

www.cross-spectrum.com

I already have one from a local distributor, not Cross spectrum unfortunately...

 

[levimax]

I think the most important points have been made. As someone who started with a UMIK-1 and now has an M23 I would sure hate to go back, but for just basic FR measurements for room correction a UMIK-1 is fine. The other application, besides speaker design, where something like an M23 becomes necessary is for sub integration (setting delays). If you want accurate and repeatable timing measurements a UMIK-1 won't work. I have read a UMIK-2 may work but can't confirm. I can confirm a M23 works and it does so many things so much better and easier with no need for a calibration file and is just such a nice piece of industrial design that if you have the funds you may want to get one to start.

 

[Blumlein 88]

I already have one from a local distributor, not Cross spectrum unfortunately...

Well I can help you develop a 90 degree cal file for it.

 

[alin_im]

Well I can help you develop a 90 degree cal file for it.

thank you very much!

attached is the calibration file provided by Dayton.

how would you do it?

 

[MAB]

thank you very much!

attached is the calibration file provided by Dayton.

how would you do it?

Measure a speaker with the mic in the horizontal (0 degree) configuration, with the 0 degree calibration file. This is your control.
Measure the same speaker with the mic's capsule in the same location, but now vertical (90 degrees). Same location is somewhat important, a few mm will suffice.
The difference between the calibrated 0 degree measurement and the uncalibrated 90 degree measurement is the 90 degree calibration.

I use 90 degree for Moving Mic Method, where you wave the mic around the Main Listening Position while playing pink noise.

 

[Blumlein 88]

Measure a speaker with the mic in the horizontal (0 degree) configuration, with the 0 degree calibration file. This is your control.
Measure the same speaker with the mic's capsule in the same location, but now vertical (90 degrees). Same location is somewhat important, a few mm will suffice.
The difference between the calibrated 0 degree measurement and the uncalibrated 90 degree measurement is the 90 degree calibration.

I use 90 degree for Moving Mic Method, where you wave the mic around the Main Listening Position while playing pink noise.

This would work and you'll know for sure. I'll adjust the OPs provided file and upload it later. Not at home right now.

 

[alin_im]

Measure a speaker with the mic in the horizontal (0 degree) configuration, with the 0 degree calibration file. This is your control.
Measure the same speaker with the mic's capsule in the same location, but now vertical (90 degrees). Same location is somewhat important, a few mm will suffice.
The difference between the calibrated 0 degree measurement and the uncalibrated 90 degree measurement is the 90 degree calibration.

I use 90 degree for Moving Mic Method, where you wave the mic around the Main Listening Position while playing pink noise.

funny enough, I was thinking to do the same thing, but I thought it might be a little too junkie to do it and I was not sure how reliable it would be. moving the microphone from one position to another, background noise etc. I will try to move the capsule in the same XYZ position and somehow minimise the background noise. if I have the mic placed about 10cm away from the speaker would that be ok? i will check a tutorial somewhere on how to measure a speaker properly.

my backup plan/long shot was to try to have a chat with spectrum labs to send me 3-4 mic measurements of same model but different serial numbers ofc and to try to find some kind of relationship between 0 and 90 and apply that formula to my calibration file.

I will definitely try to measure the speakes now that I got a confirmation from someone with experience. Thanks!

 

[alin_im]

This would work and you'll know for sure. I'll adjust the OPs provided file and upload it later. Not at home right now.

thank you much appreciated!

 

[Blumlein 88]

Attached is the 90 degree cal file for the Dayton. You can compare it to a measurement you do seeing how close it is by duplicating 0 and 90 degree measurements. Hopefully I didn't get it inverted. If so I can fix it pretty easy.
@alin_im

 

[MAB]

Attached is the 90 degree cal file for the Dayton. You can compare it to a measurement you do seeing how close it is by duplicating 0 and 90 degree measurements. Hopefully I didn't get it inverted. If so I can fix it pretty easy.
@alin_im

It looks correct:

 

[alin_im]

Attached is the 90 degree cal file for the Dayton. You can compare it to a measurement you do seeing how close it is by duplicating 0 and 90 degree measurements. Hopefully I didn't get it inverted. If so I can fix it pretty easy.
@alin_im

hi thank you for this!

did you apply an offset to the values or what was your methodology of creating the 90?

 

[alin_im]

It looks correct:
View attachment 399407

thank you for confirmation!

 

[Blumlein 88]

hi thank you for this!

did you apply an offset to the values or what was your methodology of creating the 90?

Umik's have individual cal files for each mic. The 90 degree file is a calculated file based upon the size of the capsule and other factors. So that correction curve is the same for all of their microphones. They adjust the 0 degree file by combining those values with the 90 degree difference values. Since the Dayton looks nearly identical and uses a 6 mm capsule just like the Umik, the off axis change should be the same or nearly so.

I took the Umik 90 degree file (which I have for my Umik) subtracted 0 and 90 degree responses to obtain the difference. I then applied the same level of correction to the Dayton cal file. There is no correction until nearly 1500 hz and very little until 2500 hz and higher. I did some averaging, rounding etc to fit the Umik file to the Dayton file as the Umik has more data points. The Umik goes out to 3 decimal places while Dayton's is only one decimal place. So it should be about right, certainly in the right direction and approximate amount of correction.