Thanks Don, it looks like a good technique and I have done similar with my own signals and o'scope.
Now that my measurements are computer based, I simply use a free program called HOLMImpulse to do this. It allows you to lock time between measurements and use one as your reference point. Very handy for alignment. It reads phase and (impulse) delay. This was a huge help for me in designing my crossovers.

I don't think it works on MAC OS, tho.