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Time alignment

375 Views 1 Reply 2 Participants Last post by  Eyleron
So...when Audyssey (or any other room correction program) claims to "time align" speakers and subwoofers, is that in respect to "distance" based on ping delays, or will it actually delay different frequency signals to correct for phase?

Forgive me, I know what I am trying to ask, but I am not finding the correct words to convey it. An trio of examples of what I am wondering...

First...All speakers exhibit changes in electrical phase at different frequencies. Some more than others, but still, phase changes with frequencies, especially around crossover points. From what I understand, simply modifying the frequency response will also alter this electrical phasing, as both are intertwined. Electrical phase seems to be different than acoustical phase in this respect. But still, the question asked is; besides correcting for frequency response, time alignment is tauted...is this just simple alignment based on what the mic picks up as an overall delay, or will it change the actual phase shifting that goes on with individual speakers and their own drivers?

B...the shorter the wavelength, the easier it is to find cancellation modes at each individual listening area and each listening area will have its own set of modes due to slight variations in distance between speakers. Does time alignment sense this and adjust the frequency specific phase changes asked about in the first example (if the first example was answered as a positive) to smooth for individual seating areas as an average, just as it smoothes and averages the frequency responses over these different seating areas?

#3...If both the first question and B are true, does this mean that it will also correct for multiple subwoofers in this way...delaying certain frequencies within the signal so that all subwoofers are essentially in phase with eachother at all points of the frequency spectrum?

If this is the way these programs work, then they are powerful and awesome. If not, then I wonder what these programs truly have over patient fully parametric EQ followed by the processor setting delays and crossovers.

Any help would be appreciated as I am wondering if Audyssey or the Emotiva brand of frequency/time room corrections will best the careful parametric EQing that I have been doing for over a decade.

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I believe time alignment is not per frequency or frequency band, but rather the entire signal. As is the delay setting for your speaker distance in the receiver.


You don't really want every frequency of the subs to have the same modal reinforcement, as that would just accentuate certain frequencies and wouldn't destructively flatten peaks.

Your sub(s) is already interacting with the room to create the big peaks and valleys in the response. 

Moving one sub and the audience yields a different modal response. You find the least worst.

Adding more subs that have different modal responses "smooths" the overall response heard by the audience.


Read the Harmon paper, read about the Geddes method, buy two or three subs, and hope that Audessey does a good enough job, or play with REW to see the response and tweak further. The latter is almost necessary to start with the best response for Audessey to work from.
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