ECM8000 Orientation and Cal Files

[Anthony]

I don't usually link to other forums here, but here's a discussion about the ECM8000 mic and cal file over at DIY Audio:

http://www.diyaudio.com/forums/showt...hreadid=119164

What it comes down to is this:
1) if you use the ECM8000 cal file posted here at the shack, be sure to use it in the vertical position!!! That is all the cal file is good for. The response of the mic changes when horizontal

2) The old cal file we used to have here was actually pretty close to the horizontal orientation plots of the ECM8000 (and what was printed on the Behringer website/box)

3) There is a lot of variance in ECM8000 mics. We may have been lucky here to get so many that agreed.

4) The only way to be sure is to have it calibrated yourself for about $120

5) This pretty much only applies to high frequencies (3k+) The mic is pretty flat below that down to 40 Hz or so and many cal files seem to agree on the LF rolloff.

So consider this a PSA if you use the Behringer for full-range EQ work but are seeing weird results in your top octaves. In my case, I am measuring flat and hearing dull, or measuring ultra bright and hearing flat. Now at least I have an explanation for it.

[lcaillo]

The calibration file does not affect the position. If you want to compare to responses that others display, it may be more appropriate to use the same orientation, but the cal files were not made with regard to room effects. Generally it is suggested here to use a vertical orientation. I suggest trying both and see what differences you get in your setting.

Any time that you use calibration values from another's equipment, you are shooting craps to some degree. The point is no less valid with this mic. There are trends in any product, however, that may mitigate the problem. In this case, over the range of frequencies that most use for calibrating subs with REW, the variance is not as great. At frequency extremes, both high and low, they will be greater. Most folks are not building 10Hz subs nor calibrating at high frequencies. If you are, or if you are getting unexpected results, I strongly suggest getting your mic calibrated. Anytime you can reduce variables you will likely spend less time chasing your tail solving a problem.

[Anthony]

You make some good points, but my main point was Svante over at DIYaudio used the same mic at different angles and got very different results in the top octaves. The graphic is about half way down the page.

The hump at 10kHz on axis goes away when the mic is perpendicular. however the mic then rolls off very fast from 10kHz to 20kHz. This is due to the baffle effects of having a 12mm mic (see chart later in the thread when the ECM8k is compared to the baffle response of a 12mm circle).

So it is VERY important to know what orientation your mic is calibrated for because the results will change if you mount it otherwise.

Agreed, though, that this effect is only important for higher frequencies. For subs, any of the "standard" cal files will probably do fine.

[brucek]

but here's a discussion about the ECM8000 mic and cal file over at DIY Audio

I looked at the posts and graphs you're referring to at DIY audio. I think you need to be cautious when testing microphones, since small mic element positional differences can account for some large changes in response that aren't due to the actual microphones response differences.

In addition, where you're not testing in a controlled environment, rapid changes in system response can occur, and even the smallest positional difference in a mic element can exaggerate the outcome. Where I see a comparison that shows the tests done at many centimeters apart between the elements, I don't assign it much validity I'm afraid..... (just my opinion, please, no cards and letters).

As I said in your other post on this subject, If you're concerned about accuracy beyond home use, then you should get your microphone calibrated. We make no claims about the accuracy of the cal file we provide for download other than it is correct for the mic for which it was carried out.
As a free service we provide this file for anyone to use with their ECM8000 knowing that it may not be absolutely accurate with their ECM8000. For home use, a movement of the mic element a few feet can easily result in several dB of level change, so it would be fine to use in a home theater...

brucek