# How to do time alignment using Excess Group Delay?



## mojozoom (Sep 25, 2012)

Can someone describe the method to do time alignment of drivers using Excess Group Delay (EGD)?

I have tried it with a sub and mid that both cross at 80 hz, and my results weren't extremely conclusive. I am already pretty sure of the correct alignment for the two, so it's interesting to see what is predicted with EGD.

What I saw was a spike at 80 hz that got narrower at the base but higher as I increased the delay of the mid to approach the phase of the sub. When I hit the correct delay setting the spike dropped to just an almost indiscernable bump.

But what confused me was that as I increased the delay of the mid further, I didn't see any other changes. It just stayed flat at 80 hz. I had expected a new spike at 80 hz to show up indicating the phase mismatch that was occurring as I kept increasing the delay.

Any thoughts? Thanks!


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## JohnM (Apr 11, 2006)

Excess group delay is not a good indicator of alignment. The combined response can be minimum phase over quite a wide range, for all of that range the excess group delay will have little to show as there is no excess. There are a couple of threads on time alignment that may be useful:

Using REW to time align drivers or subs to mains

Tutorial for good time alignment


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