Hi,
does anyone know where can I find specs or measurements of THD and IMD performance of the mic itself ?
I have searched and found bits and pieces of information here and there but no full range specs or measurements. I am interested in finding the THD and IMD performance of this mic across the band i.e. 20hz-10Khz.
does anyone know where can I find specs or measurements of THD and IMD performance of the mic itself ?
I have searched and found bits and pieces of information here and there but no full range specs or measurements. I am interested in finding the THD and IMD performance of this mic across the band i.e. 20hz-10Khz.
This is a good question and I'd love to see the specs. Don't think I've ever seen mic distortion specs. An actual plot would be even better.
I use the ECM-8000 to measure distortion of speakers, but can really only use it as a relative measurement as I have no idea what the distortion of the mic is.
I use the ECM-8000 to measure distortion of speakers, but can really only use it as a relative measurement as I have no idea what the distortion of the mic is.
Contact Herb with Cross·Spectrum Labs - Sound | Vibration | Engineering
Nice guy that can also provide calibration for your mic.
Nice guy that can also provide calibration for your mic.
Cross-Spectrum Microphone Calibration Service - USA - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com
Cross-Spectrum Microphone Calibration Service - USA - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com
Herb's ACO mic is probably pretty low distortion at the levels being measured so its distortion is probably mostly due to the speaker. The Behringer mic's distortion would be the difference between the two mics.
Cross-Spectrum Microphone Calibration Service - USA - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com
Herb's ACO mic is probably pretty low distortion at the levels being measured so its distortion is probably mostly due to the speaker. The Behringer mic's distortion would be the difference between the two mics.
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I've wondered about this as well but likewise didn't find much in the way of data. Can't comment on the ECM8000 but with the Dayton EMM6 I have (cal'ed from Herb, pretty similar to the old ECM8000s) I've measured THD as low as -55dB, which is basically a measurement of the noise floor. So it seems good enough.
In my experience THD's usually a reasonable proxy for IMD so I'd expect IMD levels to be comparable.
In my experience THD's usually a reasonable proxy for IMD so I'd expect IMD levels to be comparable.
I wish the same thing would have been mentioned for a few more frequencies as well in addition to 30hz and 1Khz.
Also, I too am interested in knowing about distortion figures only in the sub-120db level - more like in the 90-95db range. I really dont care about how much spl the mic can handle before reaching a said amount of distortion.
None of these Panasonic-based mics are going to distort enough at 90dB to worry about. As twest said, it will be down in the noise floor. The noise is fairly high with my Dayton, ~39 dBA as measured by Herb.
Edit: that's the total A-weighted noise summed across the audio band. The noise will be lower at any particular frequency.
Edit: that's the total A-weighted noise summed across the audio band. The noise will be lower at any particular frequency.
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Correct. I haven't done a gain cal of my mic preamp to work back to absolute SPL from Herb's sensitivity cal on the mic but mostly what I care about is THD at the crests of typical listening levels. So roughly 75 or 80dB SPL @ 1m---can't test into the mid 90s as I'd wake up the neighbors. It'd be nice to lift the signal farther off the ambient, but I've been able to get fairly decent results in quiet mornings with little wind, traffic, and not too much flow in the river.
I should point out that's above 1kHz or so; below that the noise floor comes up and by 20Hz the test tone's often lost in the ambient. The dropout on meaningful THD's usually around 700Hz; low enough to get a decent sense of how most woofers perform. The few hundred Hz range is still good enough you can estimate where the wall is on most mids and cross accordingly, though there's less information than I'd like. One of these days I'll get around to getting a cal'ed supercardiod and seeing how much it improves the SNR; omnis aren't really a good choice for assessing raw driver performance.
Hi all, Herb here.
Percy emailed me yesterday about putting together THD/IMD tests. I did a little experimenting and I think ARTA gives me the building blocks to do THD measurements. IMD is a little less certain since, to do it right, I need to good identical sources which I'm not sure I have right now.
I have a shipment of ECM8000s coming in later today that I'll play around with and I'll try to post back here in a couple of days.
Percy emailed me yesterday about putting together THD/IMD tests. I did a little experimenting and I think ARTA gives me the building blocks to do THD measurements. IMD is a little less certain since, to do it right, I need to good identical sources which I'm not sure I have right now.
I have a shipment of ECM8000s coming in later today that I'll play around with and I'll try to post back here in a couple of days.
Herb, ARTA will do IMD in spectrum analyzer mode with a 2-sine signal. Go to Generator - Configure to set the frequencies. Go to View - Info and check Distortion to show it in the status line. Go to Setup - Spectrum scaling (yeah I know, really illogical) and check what kinds of distortion you want to show. I just leave them all checked.
For HD sweeps, you can either do it in ARTA or STEPS.
In ARTA, use Impulse mode with a single channel swept sine signal. In the Generator setup, check the 'Center impulse response' box. Then go to Analysis - Frequency response and distortion after you record the impulse.
STEPS takes longer but it can display the curves in % distortion rather than dB.
For HD sweeps, you can either do it in ARTA or STEPS.
In ARTA, use Impulse mode with a single channel swept sine signal. In the Generator setup, check the 'Center impulse response' box. Then go to Analysis - Frequency response and distortion after you record the impulse.
STEPS takes longer but it can display the curves in % distortion rather than dB.
If not yet seen, this might interest some - audioXpress had an article on the distortion profiles of the wm61 capsule, stock and Linkwitz modded. I've posted it to this forum sometime in the past, but its relevant here, so I'll just post the pdf. Thanks to aX for making this available!
EDIT - its too big! Here is the link: http://www.audioxpress.com/magsdirx/ax/addenda/media/danavaras2861.pdf
EDIT - its too big! Here is the link: http://www.audioxpress.com/magsdirx/ax/addenda/media/danavaras2861.pdf
Awesome, Herb! Look forward to seeing your results.
The rapids are about 0.5km away, 100kmh arterial about 1km away. Both create SnR problems if the wind's bringing noise from them; passband magnitude measurements are fine except for the low bass, but if I want good stopband, distortion, or phase data I have to wait for a different wind.
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