Distortion Measurement

Thread Starter
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Feb 8, 2018
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REW is a very flexible and very complete software, but like all software it can always be improved.
By measuring the SPL of any device, it is possible to display the THD distortion and also the distortion
level of the individual harmonics.
I always wondered if it was possible to compensate, in addition to the level and the phase, the distortion
in the calibration phase of the measurement system. If it were possible we could measure the distortion
of a device net of the distortion of the measurement system, this would allow us to make more accurate
measurements of devices that have very low distortion levels. For example HiFi amplifiers ...

Regards
Antonio
 

John Mulcahy

REW Author
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Apr 3, 2017
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There is an extensive thread on that topic here. Compensation is level and (somewhat) time dependent, so implementation is by no means trivial.
 
Thread Starter
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Feb 8, 2018
Messages
279
Location
Italy
Certainly the distortion is also dependent on the levels of the DAC converter output signal and the level of the ADC Input signal.
To simplify everything it may be necessary to normalize the output signal and the input signal of the system so as to be sure that the levels to be measured are the same as those of the calibration phase. I realize that this is not at all simple, but certainly not impossible.
 
Thread Starter
Joined
Feb 8, 2018
Messages
279
Location
Italy
For speaker response measurements, such compensation is certainly not very useful, in fact loudspeaker systems normally have
distortion values much higher than that introduced by the electronics of the measurement system.
Compensation only makes sense when evaluating a device the electronic, in this case it may make sense to carry out the
compensation only if the level of the output and input signal are close to the calibration levels of the system, for example +/- 1db.
In this case, perhaps it would also make sense to insert a new type of measurement in the REW Measurements panel, for example Response,
that can refer to a specific calibration file to compensate for the distortion.
Thanks for your attention
 
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