# How to use the rta function in REW5



## gperkins_1973 (Aug 25, 2008)

Hi there,

Could someone explain to me how you use the rta function. When I click on the measurement I took and click on rta another window comes up which is fine but when you click on the THD button it says it is not available. I would like to work out what distortion values my subs are.

cheers

Graham


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

This thread may help.

Regards,
Wayne


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## laser188139 (Sep 19, 2009)

It's not a great test, Graham, but I tried this on my laptop using just its builtin uncalibrated mic. If I try RTA with broadband background noise, it reports Distortion N/A. If I start the internal REW generator, specifying Sine Wave, and reset the averages, THD numbers now appear. As discussed elsewhere, REW calculates THD based on a single sine wave signal. It appears REW v5 now has an internal check to prevent people being confused by asking for a THD calculation when the signal does not appear to be a single tone. 

Bill


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## gperkins_1973 (Aug 25, 2008)

Bill,

Thanks for that I will give it a good read. I am interested in what distortion my subs are showing at certain frequencies at certain volumes. 

cheers


Graham


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