Using Excess Group Delay for aligning speakers

[AustinJerry]

The REW Help Guide states "Excess group delay is a useful plot for time aligning speakers." Perhaps I missed it, but I don't see a discussion of how to interpret the EGD measurement WRT speaker alignment. Can someone point me to a "how to" discussion? And is EGD a better/more accurate method of analyzing speaker alignment than the Impulse Response with Acoustic Timing Reference?

Thanks.

 

[John Mulcahy]

It depends a little what is meant by timing alignment. Alignment between speakers can be done with the acoustic or loopback timing reference, making use of the system delay figures. Alignment between drivers in a speaker or between sub and main can be helped by looking at excess group delay, since it primarily shows the time shift versus frequency. At the listening position it does typically have lots of spikes at sharp dips or nulls in the response though so it can be hard to identify the underlying time offset. The wavelet spectrogram is probably more useful for driver alignment, using the Peak Energy Time trace.