# first measurement



## mitja (Jul 26, 2012)

Hi !

This is my first measurement with REW.
Also new in forum.

I use Behringer ECM 8000 and Generic cal file. (and m-audio fast track pro USB interface)

I was testing LS response left + right speaker 1/3 smoothing.
The speakers are small DIY build and run in small mode cut off 120dB.


I am concerned about cal. of the ECM 8000 must i try to measure withaut cal file?
The region 5000 and higher looks strange to me.

Please can someone look at the measurement .

Thank you:wave:


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## Barleywater (Dec 11, 2011)

How was measurement made? What was microphone distance, orientation; and was microphone used with stand?

Statistically generic mic cal file may be useful, but ECM8000 has proven need for individual calibration file for peace of mind results at low end and high end:











Have you performed sound card loopback calibration?

If you post saved measurements as .mdat file I will give a thorough look in terms of technique and performance.

Regards,

Andrew


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## mitja (Jul 26, 2012)

Thanks for the fast response.

I did the loop back and calibrated the sound interface and also did the SPL meter cal. 
But I did not use a mic stand 

The mikrophon was placed pointing up and 10 degr. forward.
The distance from the LS to the mic also my listening position is 4m or 13 feet.
the room is 16,5(5) feet 36(11m) feet and 9,5 (2,8)feet high. 
the room is untreated and has some huge RT 60 parameters and long decay times.?onder:
That is why i am using the REW (to tread the room -that is in fact 1/2 of the house)

I hope i did not mes up the m to feet conversion. 




View attachment prva meritev 20.9.2012.mdat


thanks!

this is the best forum EVER.


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

mitja said:


> The mikrophon was placed pointing up and 10 degr. forward.


 That explains at least some of the high-end droop. Our generic calibration file is 0° incident, which means it was produced with the mic at a horizon orientation. Using upright (90°) mic orientation with a 0° calibration file will result in measurements with reduced high frequency levels. Measure with the mic pointing at the speaker, and tilted up slightly – maybe 20°.




> this is the best forum EVER.


Thanks for the kind words! “T

Regards, 
Wayne


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## mitja (Jul 26, 2012)

I will make some mike position tests and post the changes 

Thanks for the advice .


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## Dwight Angus (Dec 17, 2007)

My mike was also pointed at the ceiling and probably caused the high end droop I am seeing. I will point the mike at the speakers up 20 degrees.


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## mitja (Jul 26, 2012)

Red- mic pointing up(cal fine loaded)
Blue- mic pointing at the speakers 20 dgr. up (cal file loaded) 
green-mic pointing at the speakers 20 dgr. up (no cal file)









i think custom cal file is the best way to go. Or?

:scratch:


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## Barleywater (Dec 11, 2011)

ECM8000 if anything tends to exaggerate high end. Close examination of impulse response from above posted mdat indicates some early, and some very early strong reflections. These are likely creating a comb type filter that is seen as roll off above 5-6kHz. Impulse response at <0.5ms (500microseconds) suggests problem starts right at tweeter/baffle, so may very well be design problem. Joys of DIY. 










200u is about 2.7 inches. To get reflection path length difference this small suggest tweeter is not flush mounted, or is some type of horn, intended or not. With tight gating SPL looks like this:









Please post details of speaker. Drivers, layout, crossover.......picture. How close was microphone to speaker for measurements?

Regards,

Andrew


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## mitja (Jul 26, 2012)

HI !

Here are pics of my speakers and FR of the DIY kit by the manufacturer .

The distance of the mic to the speakers was 4m (13 feet). And i tested only L + R speaker together .


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## Barleywater (Dec 11, 2011)

Signal captured in previous post is very good for 13ft.

Two speakers together could also well be source of comb effect >5kHz. Measure speakers individually to confirm.

Ported box based on impedance plot. Yes?

From measurement conditions, and nice pics of setup, looks like you can get right into integrating sub.

Regards,

Andrew


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## mitja (Jul 26, 2012)

Hi

Yes it is a ported design speaker.

I will play around with the settings and measurements and continue with the process of learning.

Thanks for the advice !:reading::T:T:T


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