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Good day everybody,

I have a question regarding the calibration of my speakers. I want to measure the Impulse-Response of several rooms with REW and I have an external USB Mic (UMIK-1) and an external speaker, all connected directly to the laptop.
In REW it is possible to account for the calibration of the microphone but I don't see where I can also specify the calibration of the speaker (theoretically the response of the speaker should be flat for all frequency spectrum but I need to take into account also small variations for my work, a high accuracy is needed).

I have seen that only an SPL calibration is possible (with an external SPL meter) but this gives only the response of the speaker for one single frequency (10 kHz). Is there any way to upload the calibration file of the speaker?

Thanks a lot for the help!
 

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To remove the effect of the anechoic speaker response (assuming you have that or a decent approximation to it) you could load it in place of the soundcard cal file or do a bit of work in a spreadsheet to add it to the mic response and have a combined mic cal file that covers both. Note, however, that REW only uses the cal files for its frequency response plots, the measured impulse response does not include the cal file responses.
 

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Discussion Starter #4
thanks for the answers,

ok let me be sure that I understand it properly: the IR function that REW gives is just the recording of the SPL as a function of time, what a normal recording software would do but in this case for a sinusoidal sweep instead of a random sound. If I also want the frequency response then REW performs the FFT to the IR and adjusts the frequencies by reading the calibration file.

If my goal is to covolve the IR function of a room with a given input signal using for example the software SIR audio tools (in Audacity), this software should be the one that takes into account the calibration file because it is where the FFT is performed, right?

regards,
 

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tthe IR function that REW gives is just the recording of the SPL as a function of time, what a normal recording software would do but in this case for a sinusoidal sweep instead of a random sound.
Not quite, the IR is derived by dividing the FFT of the captured signal by the FFT of the sweep signal and then taking the inverse FFT of the result.

The IR that REW measures does include the influence of speaker and mic however. There isn't an easy way to separate those. If you had a measurement with speaker and mic in an anechoic chamber you could use REW's trace arithmetic feature to divide the in-room measurement by the anechoic measurement to extract the room's contribution, but because mics and speakers have roll-offs at low (and sometimes high) frequencies this causes noise levels in the resulting IR to be boosted in the regions the mic+speaker response rolls off (which is one of the reasons REW doesn't do this, the other is that it makes it very difficult to remove or change a cal file and its effect).
 
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