Roger Jönsson of Line Audio states this:
”Alla OM1 går igenom mätningar och trimning i flera steg. Klarar de inte väl inom +-1dB on axis (mot mina Earthworks M30) så blir det kapselbyte tills de passerar. Oftast ligger de inom +-0,5dB om man begränsar mätningen till 19.5 KHz. Basen kan diffa något lite mer, pga osäkerheten hos M30.
Ca 25% av OM1-kapslarna blir skrot eftersom de inte passerar mina gränskrav.
För mycket av högtalarmätningar duger nog OM1 rätt bra ändå. Däremot är de lite för riktade för akustikmätningar i diskanten.”
That is in swedish… I Quick translation.
All OM1 are measured and trimmed i several steps. If they do not measure within +-1dB on axis (compared to Earthworks M30), the capsule will be changed until they pass. Often they measure within +-0.5dB if limitied to 19.5 kHz. Bass can differ a bit more, due to the M30.
About 25% of the capsules are thrown away as they do not fulfill my requirement.
For most measurement of loudspeakers, the OM1 will do well. For measuring acoustics they are a bit too directional at higher frequencies.
I have used the cardioids from Line Audio, CM-3 for recordings. They are really excellent mics, though i have not tried to confirm their specced FR.
I bought a measurement mic from sonarworks, which comes with a calibration file that you can load in REW. It's pretty cheap. I assume it is very similar to other budget mics (it certainly looks the same) such as from behringer, the umic-1 or others. Generally i think most budget measurements, while certainly not the last word in accuracy, are pretty decent and enough to get you started. If you couple measurements with listening i dont think a few dbs at the high end will make or break your loudspeaker design.
I bought a measurement mic from sonarworks, which comes with a calibration file that you can load in REW. It's pretty cheap. I assume it is very similar to other budget mics (it certainly looks the same) such as from behringer, the umic-1 or others. Generally i think most budget measurements, while certainly not the last word in accuracy, are pretty decent and enough to get you started. If you couple measurements with listening i dont think a few dbs at the high end will make or break your loudspeaker design.
OK, seems like this is the real deal. But $975? Why spend that much when you can get a calibrated mic for $50-$75 that is plenty "good enough" for DIY measurements? That's really a question from me - maybe I just don't understand what the extra $900 is buying you in this case...
Very good price for a measuring microphone with a tolerance of + - 1 dB. On the site of their manufacturer, I also saw a microphone preamp - the same excellent performance, lacking only usb output.
Even the cheapest microphone can be compensated to give "flat" response using a calibration file. As long as you're looking for a quick solution to get a "flat" measurement, all you need is a cheap microphone with a good calibration file. Getting accurate calibration data is not trivial and tends to be expensive. I wouldn't rely the factory calibration data that come for free (or very little extra money) with a cheap microphone. Good calibration data will be $50 or more.
However, in my experience, the cheaper microphones start drifting away from the original calibration data within a year or so. The cheaper microphones also tend to have much higher distortion and noise.
It really depends on what you need. I am done with cheap microphones (nothing but trouble).
How about a audiomatica (clio) mic, they have pretty flat freq response with no need for a correction file. They also has some useful accessories like the calibrator adapter.
But they need a battery box/power supply to operate, does anyone know about a suitable circuit? They seems to need/like 8.2v/5.6kohm.
But they need a battery box/power supply to operate, does anyone know about a suitable circuit? They seems to need/like 8.2v/5.6kohm.
Even if the Audiomatica mics tend to have "flat" response, there will be some variation between different units. You therefore need a reliable measurement of your specific unit in order to know how "flat" your unit is. And once you have these data at hand, you can also use it to compensate your measurements.
That is true, but the accuracy of the Audiomatica mic, as is, is good enough for my needs. I do not need a calibration file. I trust Audiomaticas specs. But I do not trust cheap mics from behringer, dayton, minidsp and similar and their specs. Line audio om1 is a nice alternative and seems to be the best mic for value and high precision
The Audiomatica microphones are at least times the price of the Line Audio OM1. Do we know anything about the accuracy of the Audiomatic microphones over time or between samples? There are not that many suppliers of mic capsules and those who make microphones for measuring use to select the capsules. Spoke to iSEMcon in Germany and was told that a fraction of the capsules could be used back then when they used the Panasonic capsules.
For hobbyists, I find the miniDSP Umik-1 a good choice as it comes with double calibration (within +-1 dB) and a built-in mic preamp. The price is just a fraction of what an Audiomatica + interface costs. For professionals, the "real" measuring microphones are first choice but they still need calibration from time to time. Not the cheap one but the expensive accredited calibration.
For hobbyists, I find the miniDSP Umik-1 a good choice as it comes with double calibration (within +-1 dB) and a built-in mic preamp. The price is just a fraction of what an Audiomatica + interface costs. For professionals, the "real" measuring microphones are first choice but they still need calibration from time to time. Not the cheap one but the expensive accredited calibration.
I personally use UMM-6 Dayton microphone.
You can download the calibration file for your specific sample on Dayton website. (On my side the correction is just -1.5dB high shelving at 3kHz).
It's directly powered by usb and works pretty well with REW software.
Dayton Audio UMM-6 USB Measurement Microphone
You can download the calibration file for your specific sample on Dayton website. (On my side the correction is just -1.5dB high shelving at 3kHz).
It's directly powered by usb and works pretty well with REW software.
Dayton Audio UMM-6 USB Measurement Microphone
Checking for drift does not require "accredited calibration". All you need is a sound source and test setup that is reproducible over time. You might get happy with a speaker and well documented setup (microphone position etc.). Maybe add a second microphone to the picture to see if the difference between the two changes over time. The advantage of doing such tests from time to time is that you know what your data is worth.
In my (somewhat extreme) view, accreditation does not much in terms of "how good" the data is. It just allows attaching a "nice" label to the equipment/data, and it makes it easier to blame others for any issues ("my lab is accredited, so it must be good." or "my data comes from an accredited lab, so it must be good"). If you need accredited labs/data, you'll pay for it, no matter if you have "hobby" or "professional" microphone (whatever that might be).
There are several interlocking issues here.
First the "professional measurement microphone" had meant metal diaphragm condenser microphones, usually from B&K. Those have demonstrated stability such that they don't change over time. That was not true of other metal diaphragm condenser microphones in the past. Those did not have as solid a mounting for the diaphragm. The few other vendors have improved their microphones and I'm sure they are much better now.
However several companies (starting with Earthworks) have been successful with commercial electret capsules, making for much less expensive microphones. They need to do extensive testing and screening of capsules with a yield of 1 in 10 for those microphones. Unfortunately the plastic diaphragm is not quite as stable and those do need periodic checking for sensitivity.
Now lets separate sensitivity from frequency response. Sensitivity is knowing that 94 dB is actually 94 dB +/- some small value. frequency response is the response curve meaning difference from the reference level vs. frequency. Typically the response curve is what you care about for speakers. The absolute level is less important. Even B&K uses different methods of checking sensitivity and response. Their methods won't work for the commercial electret microphones so those would be checked using some sort of free field setup referenced to a known standard. Its important to understand that the on axis measurement won't necessarily give details about the off axis performance. And the number of errors and confounders in this process limits its actual accuracy.
The modestly priced microphones that come with curves are probably good for 1-3 dB response accuracy and similar sensitivity accuracy. I think the better ones show those limits. In other words, don't chase the last dB with one. You will be going in circles. They can be great for relative response measurements and an out of phase or poorly optimized crossover will show just fine. Getting "flat" response to 30 KHz will just be that microphone's error not a real picture.
First the "professional measurement microphone" had meant metal diaphragm condenser microphones, usually from B&K. Those have demonstrated stability such that they don't change over time. That was not true of other metal diaphragm condenser microphones in the past. Those did not have as solid a mounting for the diaphragm. The few other vendors have improved their microphones and I'm sure they are much better now.
However several companies (starting with Earthworks) have been successful with commercial electret capsules, making for much less expensive microphones. They need to do extensive testing and screening of capsules with a yield of 1 in 10 for those microphones. Unfortunately the plastic diaphragm is not quite as stable and those do need periodic checking for sensitivity.
Now lets separate sensitivity from frequency response. Sensitivity is knowing that 94 dB is actually 94 dB +/- some small value. frequency response is the response curve meaning difference from the reference level vs. frequency. Typically the response curve is what you care about for speakers. The absolute level is less important. Even B&K uses different methods of checking sensitivity and response. Their methods won't work for the commercial electret microphones so those would be checked using some sort of free field setup referenced to a known standard. Its important to understand that the on axis measurement won't necessarily give details about the off axis performance. And the number of errors and confounders in this process limits its actual accuracy.
The modestly priced microphones that come with curves are probably good for 1-3 dB response accuracy and similar sensitivity accuracy. I think the better ones show those limits. In other words, don't chase the last dB with one. You will be going in circles. They can be great for relative response measurements and an out of phase or poorly optimized crossover will show just fine. Getting "flat" response to 30 KHz will just be that microphone's error not a real picture.
I have searched for a less expensive Bruel & Kjaer option.
GRAS are also Danish and probably nearly as expensive, and they are rare in the second hand market which doesn't help.
ACO Pacific may have what I want but the website sure doesn't inspire confidence, makes it awkward to find products.
I just learned that Rode plan to make a measurement mike, this may be the one.
I believe their reputation in the studio market is excellent - Some of the classic makers seemed to rest on their laurels and use them to over-price their products.
A similar move in the measurement market will be fun, hopefully soon.
Anyone have advanced information?
David
The tread started with "Microphone for measurements" not "professional measurement microphone". As this is a DIY forum, I think most of us are not looking for very expensive test equipment to verify our DIY projects. Sure, B&K or GRASS are in a different class than "toys" like Behringer/Dayton/miniDSP. There is also a lot of knowledge needed to interpretate/understand the measurements.
'Xactly! I'm searchin for equipment to test and tune my upcoming speaker project (a derivative of the JBL 4430 monitor).
Best regards!
Best regards!
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