Hi there,
Couple months ago I decided to step up my audio measurements "game". Bought dbx RTA-M uncalibrated microphone (no downloadable file, no mentioning that it is somehow calibrated, just the overall quality claims from manufacturer). It was praised by local salesman, who had just this one and couple of other models in stock with similar pricing. None of them with calibration file. As it was my first reasonably good measurement microphone, I assumed, that it is more or less flat and is more than sufficient for homemade speaker projects. But the doubts were there and...
I bought cheaper, but calibrated Dayton EMM6 couple days ago and... Now I got real headache. Below are the measurements of dbx and dayton. No matter what levels, no matter what REW options - the curves are exactly like this:
I admit, that the speaker Dayton PS95-8 I am measuring has some rising response, but it is around the levels of dbx, which is similar to manufacturer curve, I do not fully trust dbx, but Dayton is DOA, landfill or similar quality. Calibration file of Dayton is in ~3dB range, there is no curve similar to ~20dB difference. Or maybe I am doing something very very wrong?
My ears are good and I understand that I am not measuring flat speaker with flat microphone, but the real perception of sound is in the dbx curve.
p.s. I will try to get some local help to compare my mics to the some more expensive one, stay tuned.
p.p.s. dbx was used ~10 times/days, dayton ~2. There are no damage signs on any of them, they are new and look as new. Handled with care when in my posession.
Couple months ago I decided to step up my audio measurements "game". Bought dbx RTA-M uncalibrated microphone (no downloadable file, no mentioning that it is somehow calibrated, just the overall quality claims from manufacturer). It was praised by local salesman, who had just this one and couple of other models in stock with similar pricing. None of them with calibration file. As it was my first reasonably good measurement microphone, I assumed, that it is more or less flat and is more than sufficient for homemade speaker projects. But the doubts were there and...
I bought cheaper, but calibrated Dayton EMM6 couple days ago and... Now I got real headache. Below are the measurements of dbx and dayton. No matter what levels, no matter what REW options - the curves are exactly like this:
I admit, that the speaker Dayton PS95-8 I am measuring has some rising response, but it is around the levels of dbx, which is similar to manufacturer curve, I do not fully trust dbx, but Dayton is DOA, landfill or similar quality. Calibration file of Dayton is in ~3dB range, there is no curve similar to ~20dB difference. Or maybe I am doing something very very wrong?
My ears are good and I understand that I am not measuring flat speaker with flat microphone, but the real perception of sound is in the dbx curve.
p.s. I will try to get some local help to compare my mics to the some more expensive one, stay tuned.
p.p.s. dbx was used ~10 times/days, dayton ~2. There are no damage signs on any of them, they are new and look as new. Handled with care when in my posession.
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tktran303,
Thank you with response, but have you seen my measurements???...
In your examples differences between some 30 to 250EUR and above mics are in 3dB range at most, with 30EUR old mics being least accurate.
My charts are 20dB(!), which means either mic is terribly bad, or I am doing smth very very wrong. BTW, the switching of microphones was like this: off shadow 48V, switch mic, 48V shadow on. That is all. I am thinking of all the things I could do wrong, but the other mic is not showing irrelevant measurements.
Thank you with response, but have you seen my measurements???...
In your examples differences between some 30 to 250EUR and above mics are in 3dB range at most, with 30EUR old mics being least accurate.
My charts are 20dB(!), which means either mic is terribly bad, or I am doing smth very very wrong. BTW, the switching of microphones was like this: off shadow 48V, switch mic, 48V shadow on. That is all. I am thinking of all the things I could do wrong, but the other mic is not showing irrelevant measurements.
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it has been voiced in other threads that the calib files for the cheaper mics are suspect.
another point to note is that even mid priced mics often dont specify how tight the calibration is i.e. within +/- 1dB over a specified range
another point to note is that even mid priced mics often dont specify how tight the calibration is i.e. within +/- 1dB over a specified range
There is no calibration to help from -20dB. That is ~16times less sound power if I am correct.
I am doing smth wrong, or my luck is just bad.
Below attached measurements of EMM6 with cal file
I am doing smth wrong, or my luck is just bad.
Below attached measurements of EMM6 with cal file
Are you using these mic's pointed at the sound source or pointed 90 degrees up?
I use dbx RTA-M with much better results when pointed to ceiling.
It's not a SOTA mic, but I realize small changes in mic positioning will result in bigger difference than the calibration delta.
I use dbx RTA-M with much better results when pointed to ceiling.
It's not a SOTA mic, but I realize small changes in mic positioning will result in bigger difference than the calibration delta.
Smaller one:
Already did. It is from EU retailer. Will arrange return in couple days.
I measured with both of them directly at the sound source, not up or down. 1m from source, height from floor and distance to the closest wall is more than 1m, so no weird bounces here. Not much science here - the curves are similar at any distance I measure.
Why is the Dayton mic bad if after cal file its within spec?
Doesn't the correction curve correct the Dayton Mic? Isn't that what the cal file is for, regardless of how much it strays from ideal without cal file?
Appears to be +/-2db after cal file...per spec, no?
Neither mic would be accurate used without a cal file....
Doesn't the correction curve correct the Dayton Mic? Isn't that what the cal file is for, regardless of how much it strays from ideal without cal file?
Appears to be +/-2db after cal file...per spec, no?
Neither mic would be accurate used without a cal file....
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I would first verify the electronics- A loopback from the source (maybe a resistive attenuator from the amp output) to the mike input to confirm performance. The plot looks more like a defective coupling cap or miswiring somewhere. The electret capsule in both mikes should be about the same with a response pretty flat to 20 Hz. The HF above about 5K will be a little ragged and the styling of the grid will have an outsized influence on the HF response.
A pressure response mike will have a pretty flat response free field at 90 degrees. Most electrets are free field corrected (its a tuning of the diaphragm resonanace) so off axis they roll off. The plots attached show the corrections which relate to the diameter of the microphone (there is a pressure build up as the wavelength gets close to the diameter) from constant pressure at the diaphragm. The mike spec should indicate the details of the response calibration.
When the wavelengths are short (10 KHz up) small changes in angle and distance can show big differences in response.
A pressure response mike will have a pretty flat response free field at 90 degrees. Most electrets are free field corrected (its a tuning of the diaphragm resonanace) so off axis they roll off. The plots attached show the corrections which relate to the diameter of the microphone (there is a pressure build up as the wavelength gets close to the diameter) from constant pressure at the diaphragm. The mike spec should indicate the details of the response calibration.
When the wavelengths are short (10 KHz up) small changes in angle and distance can show big differences in response.
Attachments
How Earthworks Measures Microphones
By Alex Khenkin, Director of Engineering, Earthworks
https://earthworksaudio.com/wp-content/uploads/2012/07/how-earthworks-measures-mics.pdf
By Alex Khenkin, Director of Engineering, Earthworks
https://earthworksaudio.com/wp-content/uploads/2012/07/how-earthworks-measures-mics.pdf
This one looks like a great paper, but it is a random, not related to the problem I have.
I did. It may be the problem in electronics elsewhere, not the mic, but I have two of them, and when switching them the only thing I did is pressing 48V button on audio interface twice. That is all. I am not sure if there are any reasonable recordings by not supplying shadow voltage.
Loopback cable is connected from right channel to right input on audio interface, left is signal and measurement, but in this case I was not using loopback in REW
This is outside of the corrections I would like to do. It is still with warranty and (almost) not used, so return is the only viable option.
BTW, I bought another measurement mic with calibration file: Sonarworks SoundID Reference. So I have pretty much the only two calibrated mic options which are reasonably priced and freely available in EU.
Will post measurements of all three of them this weekend
Please do nearfield measurements of both mic's, about 5mm from a woofer and tweeter cone of a two way. Adjust to get into the 90dB range. You should find quite horizontal main areas with both mic's and speakers.
If you ignore the tilt of you first measurements, they are pretty good.
It may be the DBX more suited to measuring PA stuff in a large room if there is no defect.
If you ignore the tilt of you first measurements, they are pretty good.
It may be the DBX more suited to measuring PA stuff in a large room if there is no defect.
What electronics are begin used? I've seen sound interface devices mixing what is being recorded into the play signal output, as well as some that mixed what's at the output into the record input. Some kind of cancellation might be going on. If it's a semipro digital interface, make sure that the monitor knob or switch isn't doing that.
I will retry measurements as soon as I can, right at this moment - too much noise in my environment.
Yes, it looks like exactly what you described, but there is only audio interface in signal path, only "48V" button on, and the results (were) constantly like this with this mic.
Will retest soon all 3 mics I have now.
So, retested all 3 of them:
dbx RTA-M
Sonarworks SoundID Reference
Dayton EMM-6
At 1 meter (Sonarworks is with provided cal file applied)
at ~0,005m, that is ~5milimeters (Sonarworks is with provided cal file applied), I ran Dayton at different levels, so couple of measurements of it:
Also, REW does not like that Dayton also - I get various warnings about too high distortion and similar, the distortion graphs also look not like from good microphone - 200Hz to 2kHz hovering around 8-10% , others - around 0.2-2%
Dayton is faulty. End of story.
dbx RTA-M
Sonarworks SoundID Reference
Dayton EMM-6
At 1 meter (Sonarworks is with provided cal file applied)
at ~0,005m, that is ~5milimeters (Sonarworks is with provided cal file applied), I ran Dayton at different levels, so couple of measurements of it:
Also, REW does not like that Dayton also - I get various warnings about too high distortion and similar, the distortion graphs also look not like from good microphone - 200Hz to 2kHz hovering around 8-10% , others - around 0.2-2%
Dayton is faulty. End of story.
It looks like some coupling capacitor inside the mic was too small or missing. You can see a clean -6dB decrease the lower it measures.
Now the question is, if these have been "individually" calibrated, how could that go through quality control, Mr. Dayton?
Is it just the same as these expensive woofer they sell, that are 50% off in TSP and the Dayton specialist tells you it doesn't matter (to Dayton)? Or the plate amps, all failing while having the same defects, for a decade now?
Now the question is, if these have been "individually" calibrated, how could that go through quality control, Mr. Dayton?
Is it just the same as these expensive woofer they sell, that are 50% off in TSP and the Dayton specialist tells you it doesn't matter (to Dayton)? Or the plate amps, all failing while having the same defects, for a decade now?
I have bought 9 items Dayton brand:
4units RS100 (8?)
4 units PS95-8
1 EMM-6
So far EMM-6 is faulty, also 1 unit of PS95-8 is started to make some noises - maybe it was overdriven or maybe it is faulty too. So 1 to 9 confirmed flawed goods, I cannot guarantee that 1 of PS95-8 I have is factory fault, but there were not many reasons for him to start making some noises - I am careful with volume knobs.