Help understanding Alignment Tool

[guitarplayr82]

I am trying to use REW’s alignment tool to align my studio monitors with a single sub. In the screenshot below you can see my monitors in green and my sub in brown, both of which have already been corrected with EQ:

To my knowledge the black dotted line should represent the “ideal” summing if the alignment was perfect. However, when I click “average the responses”, I end up with the teal line in the next screenshot:

The teal line is what I want/expect my response to look like, while the dotted line seems to create a weird boost around the crossover region. Why does the RMS average look so different from the dotted line? If everything was aligned perfectly, shouldn’t the response more closely resemble the RMS average since the RMS average ignores phase in its calculation?

 

[sm52]

If everything was aligned perfectly, shouldn’t the response more closely resemble the RMS average

No. And yes. Ideal alignment cannot be obtained by one action. The ideal alignment in your case is shown by a black dashed line on the upper screenshot. So that it does not look like something superfluous relative to the straight line, you need to move the frequencies of the cut of the sub and monitors from each other. Then there is a chance that the hat will become lower, closer to the main level, but the perfect phase coordination will remain. The phase cannot be ignored. With equally high -profile levels of two sources emitting the same frequency, but with opposite phases, what happens? Cancellation. You will not hear anything. Where the resulting alignment differs from the ideal, occur incomplete phase addition, which can be acceptable, or subtraction of phases, which is unacceptable.

 

[John Mulcahy]

Why does the RMS average look so different from the dotted line?

RMS average is an incoherent summation (assumption of random phases, essentially), the dotted line is a coherent summation.