# REW, nothing above 10khz with ECM8000...?



## CoolColJ (Dec 14, 2011)

I am getting massive roll off above 10 khz with an ECM8000 - is this a user error or a bug...?

Because with IK Multimedia ARC system, using the same preamp I get way more top end.

The REW pics show, both speakers together, with and without the Event Opal's onboard EQ. And then the EQ'ed left and right speakers. Followed by the ARC system screen capture


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hard to tell what you’re trying to show us with your graphs because both mention equalization in the heading, but wow - did you really EQ that 12 dB hole at 5 kHz? That’s asking for a fried tweeter.

There are at least a few reasons why you might have a roll-out at the highest frequencies.

* The speakers really don’t get up that high.
* Using a generic calibration file with the ECM8000.
* Measuring with vertical mic orientation with a horizontal-orientation calibration file.

Regards, 
Wayne


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## Rutgar (Jul 24, 2012)

If the OP doesn't mind me piggybacking onto his thread, I also have an ECM8000.

Along with the mic, I purchased the calibration files, which consist of both narrow band and one-third octave band files. I don't know which one to use, and why. Any suggestions on which to use? And, if possible, why?

Also, to the OP. I have just started learning how to use and set up REW, but I have ran a couple of 'test' sweeps (I say test because it is basically an 'out of the box sweep'), and I also get a role off above 10K. However, unlike you, I also get a sharp roll off below 50hz. Since my main speakers consist of 4 - 15" powered woofers, I guessing this has to be a calibration/settings issue. But someone here much more knowledgeable than me would need to chime in.


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## CoolColJ (Dec 14, 2011)

Wayne A. Pflughaupt said:


> Hard to tell what you’re trying to show us with your graphs because both mention equalization in the heading, but wow - did you really EQ that 12 dB hole at 5 kHz? That’s asking for a fried tweeter.
> 
> There are at least a few reasons why you might have a roll-out at the highest frequencies.
> 
> ...


The ECM8000 was 1m away from both speakers, in the centre, pointed directly ahead in between the speakers.
There was no notable difference, with and without the generic calibration file. I believe ECM8000 generally has a rise at the top end from what I gather, which the ARC system screen cap curves show - orange line.

The first pic is both speakers measured together. The blue line is flat. The red is the pass with the Opal's parametric EQ switched in to remove that bump at 200-300 hertz

The 2nd pic show the left and right speakers measured separately (with speaker's EQ switched in) and overlayed onto each other. The right speaker (red) is the one with the null at 5khz. It's interesting the null at 5khz dominates when both speakers are measured together in the first pic.
That does confuse me a bit, the 2 big dips in the upper frequencies only show up when both speakers are measured together, but not when you do them one at a time.

The Event Opals should have a frequency response over 20khz, and so should the ECM8000. I don't think my Preamp is at fault as other mics I've used to measure it, go past 20 kHz, and the ECM8000 when used in the Arc system shows a rise up top as shown in the black pic. The frequency responce graph from the Opals show it's pretty flat from 35 hertz to 22 khz. So Unless there is an error or bug somewhere, or my room absorbs all those upper frequencies...?

I'll try and hold the mic right up to the tweeter and see if things are any different


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## Wayne A. Pflughaupt (Apr 13, 2006)

Rutgar said:


> I also have an ECM8000.
> 
> Along with the mic, I purchased the calibration files, which consist of both narrow band and one-third octave band files. I don't know which one to use, and why. Any suggestions on which to use? And, if possible, why?


There should have been a disc with a “read me” file included with the mic that states the following:


> The narrow_band_response_x_degree.FRD files are designed for use with measurement and analysis programs such as Room EQ Wizard, ARTA, FuzzMeasure Pro that can make use of fine-tuned correction curves. The one_third_octave_band_response_x_degree.FRD files are designed for applications where additional smoothing is warranted or for comparison with criteria given in terms of 1/3-octave bands.


Regards, 
Wayne


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## Barleywater (Dec 11, 2011)

> That does confuse me a bit, the 2 big dips in the upper frequencies only show up when both speakers are measured together, but not when you do them one at a time.


Most likely comb filtering. At 5kHz small path length differences to speakers have big effects.

Try multiple measurements with both speakers on and moving microphone side ways 1/4" at a time between measurements. Or just play 5kHz tone through both speakers and slowly move your head.

Andrew


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## CoolColJ (Dec 14, 2011)

OK it looks like REW does speak the "truth" :whistling:

I took the Event Opals off the rubber plinths it comes with, and my heavy duty wooden stands, that are weighed down by metal plates, and put them up on small compressed felt pads (surface savers), sitting ontop sand filled and spiked Ultimate Studio stands. The position is narrower by 14 inches on each side and the tweeter is now higher than my ears by 3 inches. The sound immediately changed - much brighter, tighter, but less stereo width off course.

Set ECM8000 exactly the distance between the tweeters, in centre, front, pointed forwards.
And I get this - top end extends much further..... pic

So either the room/position, stands, the rubber mounts or all the above are causing the high frequency loss....!
I suspect the rubber plinth is responsible, but I need to measure it on/off them to be sure.
If people say speaker stands don't make a difference, then this proves otherwise  

But the massive nulls are there, 72 hertz, 6khz, and 17khz. The low end one hasn't changed much, from 79 down to 72. And now instead of the muddy sounding bump at 200-300 hz, I get at dip at 258.

Both speakers measured together


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## CoolColJ (Dec 14, 2011)

Much less variation between the speakers when measured separately now. Still rolling off above 10khz though
Red = left speaker, Blue = right speaker


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## robbo266317 (Sep 22, 2008)

I would try doing a close measurement to the tweeter to see what results you get. 
Do you have any other speakers you can measure for comparison?


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## CoolColJ (Dec 14, 2011)

robbo266317 said:


> I would try doing a close measurement to the tweeter to see what results you get.
> Do you have any other speakers you can measure for comparison?


Here is with the ECM8000 8 inches away - pic
I do have a passive set of old KRK Kroks that I could try out


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## Barleywater (Dec 11, 2011)

Look closely at measurements, ETC and spectrogram done well will show that even at 8 inches, reflections from room are clearly defined. ECM8000 body and diffuser cap cause major interactions at higher frequencies too.

Must have microphone at angle corresponding to calibration file in use, i.e. directly on axis or 90 degrees.

Gating window to <6ms will sharpen up high end.

Experiment: 

Use single speaker, locate microphone on axis to tweeter at about 8 inches. Make soundcard calibration from this setup. Use it to remeasure without moving anything, and (of course) response should be completely flat. Now move microphone 1/4" and measure again. Now what do you see?

Andrew


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## Rutgar (Jul 24, 2012)

Wayne A. Pflughaupt said:


> There should have been a disc with a “read me” file included with the mic that states the following:
> 
> Regards,
> Wayne


Got it! Thanks Wayne.


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## Wayne A. Pflughaupt (Apr 13, 2006)

CoolColJ said:


> Here is with the ECM8000 8 inches away – pic
> 
> 
> 
> ...


I think the problem is that you’re using a generic calibration file. The chart below shows the wide variance in response between ECM8000 samples, and according to a post from Herb at Cross Spectrum earlier this year, it appears that quality and consistency has taken a pretty bad hit since this graph was published.










Bottom line, a full-range reading with a generic calibration is good for “FYI” only. If you’re looking for accuracy (and it sounds like you are), you need to get your mic calibrated.

Regards, 
Wayne


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## CoolColJ (Dec 14, 2011)

Hey guys, been busy so I haven't gotten around to doing more tests.

Anyway, I'm aware of the rise above 10khz on the ECM8000, but I don't see much of a difference in REW with and without a calibration file.
When the ARC system uses the same mic to measure, you can see the rise above 10khz

If indeed my ECM8000 is actually flat above 10khz, and the calibration file is rolling it off, due to the average ECM8000 having a rise there, then I would expect the behaviour I'm seeing, but removing the file doesn't change the responce too much

The thing is, how can Behringer say the ECM8000 is flat, when it isn't? Even the graph on the box says it has a flat responce....


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## Barleywater (Dec 11, 2011)

Reading is believing? A salesman's dream come true.... I'm sure Behringer would be happy to spin you a story.

Typical ECM8000 from pic in post#14 has rise starting well before 10kHz. Pic also shows that the odd mic out of the box is respectably flat. Such microphone is likely Behringer poster child.

Have you tried placing microphone 1/4" from tweeter?

You have IK ARC package with its microphone, and an ECM8000? When you say "...a calibration file." is this through Cross-Spectrum, or something you just downloaded?


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