[RoomEq] ECM 8000 calibration file. Dec 7th 2009, 2:33pm. Scusate la domanda idiota, ma. Dove trovo il file di calibrazione di RoomEq per il Behringer ECM 8000?!? Ho fatto un giro in rete ma non sono riuscito a trovare nulla. Years ago I made a calibration file for the Sure. The Sure is only rated down to 40 hz. I am always wondering if I am getting accurate readings due to the mic and lack of a preamp.
Note: article incomplete, I need to tidy up the graphs and clarify what the lines are. I recently purchased a calibrated USB measurement microphone to help with speaker tuning. I already have a, but the Behringer isn’t calibrated, while the MiniDSP comes with a calibration file, you just download from their site keyed on the serial number of your unit. As you can see, the two units come in similar, but not the same packaging, and also look quite similar: I had been using the “generic” ECM-8000 calibration curve, but there is a fair bit of info out there that there is So why not try and calibrate the ECM-8000 using an already calibrated Mic? I know there will be inherent loss of precision during the process, but the result may still be more accurate than the generic file.
Equipment used: Laptop with Homimpulse Behringer Xenyx 1204FX Mixer Behringer UCA-202 USB interface old Windows XP laptop Homimpulse 1.4.2.0 for measurement Sound source is my “under construction” active stereo speakers with the Behringer UCA-202 connected via SPDIF output. The microphones place in a mic stand about 1M from the speakers. I’m not actually concerned too about the response of the speakers now, just that the measurements remained consistant between holmimpulse runs, which they did.
Stage 1: As a sanity test I’ll calibrate the Microphone against itself. If I can generate something resembling the calibration curve by comparing measurements with and without the calibration file applied, I should be in the right ballpark. Here are the homimpulse measurements with and without the calibration file, smoothed to 5 per octave to make the differences easier to see: Here is the “no calibration” measurement, divided by calibrated – using the Holmimpulse frequency domain manipulation functions. Turns out division (uncalibrated / calibrated) gave me the curve back. I used the raw response (no smoothing or gating) data as the source of the calculation, then smothed to 20 for visibility, phase displayed just to show mostly flat.
This is superimposed on the actual calibration curve supplied by miniDSP. To line them up exactly I had to add 2.8 dB to the calculated cuve.
From this I can be fairly sure the method I’m about to use with the Behringer ECM-8000 will give me a usable calibration curve. Stage 2: Calibrate the ECM-8000 For this I measured the ECM-8000 the same way, through the Behringer mixer and USB sound card.
I’m not concerned that much about lining up the dB magnitude as it’s arbitrary due to the level settings on the mixer (chosen to have decent headroom without clipping), so this is only a relative frequency response calibration, not an absolute dB sound level. Below is the ECM-8000 measurement, smoothed for readability to 5/octave, and superimposed on the uncalibrated UMIK-1 measurement.
The ECM8000 measurement has also been reduced by 6dB to line up closely with the UMIK measurement for comparison. They are quite close.
Calculated ECM-8000 calibration curve (red). It has been offset by -6.5 to line up with 0dB, and the UMIK-1 calibration file and generic ecm-8000 calibration file are also shown (blue and green). Smoothed to 20, although the imported calibration curves obviously are even smoother. With Holmimpulse I can export as a calibration file.
The file exported is 1997 lines compared to the 560 lines of the UMIK-1 calibration file, so possibly overly detailed compared to the source data – but using this calibration file with Holmimpulse, I do a frequency response sweep and compare against that done with the UMIK-1: And the calibrated/uncalibrated curves are quite close. With the UMIK-1 curve a bit different. So I can conclude this method probably not too useful, although the results look good.
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I recently had my Behringer ECM8000 microphone calibrated by Cross-Spectrum Labs with some interesting results (cost $50,. A very different calibration file was the result. See the attached graph - green is the stock ecm8000.txt file that comes with DRC, red is the calibration file for my ECM8000 with a Tascam US-122L preamp/USB interface.
The calibrator's experience with about a dozen ECM8000s is that though they show pretty good response (esp for the price), but they are all over the place. Haven't done a ton of listening with this, but immediately had to switch from 'normal' to 'soft' - it was just too bright and there was some occasional weird digital distortion (maybe it was clipping). Further experimentation with different target curves now required.
Edit: disregard - I think I recorded the sweeps incorrectly on my first try. Curious if others have had their mics calibrated and if the results were as surprising. Haven't done a ton of listening with this, but immediately had to switch from 'normal' to 'soft' - it was just too bright and there was some occasional weird digital distortion (maybe it was clipping)Wouldn't this suggest the calibration is wrong? In my system, with the stock ecm8000.txt file, the improvements brought by the Inguz 'normal' correction over the standard flac (on both music and Stereophile CD1 test tones) are what I would expect: flattening of a 80Hz-120Hz bump and a 60Hz trough, no difference in the rest of the frequency range which is very flat to begin with. Muski did you get a.txt file from the calibrator? Is that usaual with calibrators?
ChrisYes, it was included with the service. I think most calibrators do that. For instance, on the Earthworks audio site it says: 'Calibration files are available for every Earthworks measurement microphone at an extra charge. These files can be used to import the microphone’s amplitude frequency response directly into your measurement system.
They are in text format, with frequency in Hz in the first column, and response values in dB in the second.' Wouldn't this suggest the calibration is wrong?No, I think it was 'operator error' on my part - I don't think that I generated my first set of filters correctly. I have since regenerated everything, and am not hearing the clipping I noticed the first time with the normal filter. The sounds is a little brighter, but that may simply be that I was so accustomed to the old ones. I should do some more side-by-side listening to the calibrated and uncalibrated filters. Turns out that when I plot the 'normal' and 'soft' filters there is almost no difference between the two in terms of freq response correction.
My understanding is that the difference between 'soft' and 'normal' has more to do with the degree of phase correction. I also just read that the 'No Correction' filter just does freq filtering, with no phase correction, so I will try listening to that, too. I guess it's also possible that you might have a better instance of an ECM 8000 than mine. As I said before, I would be interested to try the same exercise with a calibrated Earthworks mic. BTW, are you using the 'normal.drc' from the Inguz site or the one included with DRC? Just curious - you say 'what I would expect'.
Is that based on published measurements of your equipment or something else? Muski, 'what I would expect' means that I am comparing (by ear) the original uncorrected sound of my system (flac files), that I know by experience to have a lumpy bass due to my particular room, but that is also pretty flat on midrange and highs, to the Inguz-corrected sound (flac/InguzDSP files). I use both test tones and music I know well. You have to compare: 1) the uncorrected sound (as above) to the standard ecm8000.txt-corrected sound; 2) the uncorrected sound (as above) to the calibrated sound. If sounds in 1) are similar on midrange and highs and the brightness only appears in 2), then the problem has to be the calibration, because unless your room is extremely dead or there is a problem with the tweeters, the Watts are pretty flat above the upper bass. I am using the normal.drc from the Inguz site.