Dodecahedron speaker calibration - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 5 Old 07-14-15, 02:14 PM Thread Starter
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Question Dodecahedron speaker calibration

Hi everyone! Greetings from Poland.

I'm building my first Dodecahedron Speaker and want to use it for some semi-pro acoustic measurements. The problem is, that most of the pro dodec's have completely flat frequency response (at least between 100Hz-10kHz). Is there a way to compensate (calibrate) the speaker within REW?

As far as I know - the power output of a speaker needs to be the same in every octave to obtain correct RT60 measurements.

Am I missing something? Can you help?

Have a great day (or night),
Andrzej
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post #2 of 5 Old 07-14-15, 03:30 PM
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Re: Dodecahedron speaker calibration


JohnM as always claimed that a calibrated mic is not necessary for acoustics measurements, so I don’t see why a speaker with flat response would be necessary either.

Be that as it may, I don’t see where compensation for this speaker would be any different than with any other speaker: Outboard equalization. Nevertheless, that seems to me to be an exercise in futility, because...

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Andrev90 wrote: View Post
As far as I know - the power output of a speaker needs to be the same in every octave to obtain correct RT60 measurements.
... the upper frequencies being generated by the speaker are directional, but the lower frequencies are not. With a dodecahedron speaker here are many more drivers generating sound that are off-axis to the measurement mic than on-axis. So even if the speaker had flat response, with our without external correction, any frequency response measurement is going to show the bottom end to be significantly tilted upwards compared to the highs.

Perhaps John can comment.

P.S. Welcome to the Forum!

Regards,
Wayne



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post #3 of 5 Old 07-14-15, 03:44 PM
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Re: Dodecahedron speaker calibration

The absolute power levels aren't critical as long as the variations are not too large and too rapid. The decay curves are calculated relative to each octave's starting point, having the level at the starting point higher or lower doesn't change the rate of decay.
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post #4 of 5 Old 07-15-15, 12:48 AM Thread Starter
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Re: Dodecahedron speaker calibration

Thank you very much for really fast response guys! I'll try external EQ with 1/3 octave bands. I may post results with no EQ as well so we can compare...

The only thing that I'm really concern about are the 'internal' phase issues of the speaker itself (produced by the standing waves within the enclosure). Logically, if there's some frequency missing in the speaker output spectrum - surely this frequency is not going to excite measured room. Right?

I forgot to mention that I plan to measure really big room. Like, REALLY big. Basically it's an industrial building that can be transformed into concert venue. I'm a sound engineer myself, but trying to get some information about the room to decide what to do next.

Last edited by Andrev90; 07-15-15 at 01:00 AM.
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post #5 of 5 Old 07-15-15, 12:21 PM
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Re: Dodecahedron speaker calibration

I don't think it would be possible to eliminate a frequency, bearing in mind the direct output of each drive unit, and in any event modal behaviour will also be excited by frequencies close to the resonance. For a very large space more challenging might be to get enough level from the speaker, but I guess you are making something suitably substantial. Use a very long sweep to capture the full response and in REW's Analysis preferences set the impulse response calculation to keep the full IR (or at least up to 9.9 seconds).
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