The effect of out of phase drivers in different speakers in a home theatre system

[dougi]

I recently added a centre speaker to my 2 channel system to get better dialog. It is now 3.1 for movies and 2.0 for music.

However, my mains are 3 way Heritage Lintons with out of phase tweeters and midrange cw woofer. Centre is a 2 way all in phase.

I have manually setup the AVR (old Denon AVR2310). I'm sure if I use Auddyssey it would complain about the out of phase.

I can't hear any immediate issues between the centre and mains but is this an issue? Would reversing the phase of the mains so that mids/treble is in phase with the centre be better? Or is comb filtering in the room so prevelent anyway due to moving around it would make little difference?

I haven't done any measurements yet but may do once I work out the easiest way to do it with the AVR and being able to feed each channel (i'm only running optical into the AVR atm so probably could test left, right for mains and L+R for centre with mains off)

 

[Adam_M]

Are you saying that the tweeter in the mains are wired out of phase with the mid and woofer -and it came that way from the factory? If that's the case, it probably means there's a 2nd order acoustic crossover between then tweeter and mid, and the crossover between the mid and woofer is 4th over.

A 2nd order slope has a phase shift of 180 degrees, so flipping the electric polarity gets the acoustic output of the tweeter and mid to align.

It would surprise me if the tweeter is acoustically out of phase with the W-M, rather than just electrically. In other words, if it were me, I'd wire everything up as intended and go with it.

 

[dougi]

In mains, tweeter and mid -ve polarity, woofer +ve. Centre all +ve. Given phase most sensitive in bass I have left as is. Music in 3.1 sounds fine, image seems stable.

 

[Adam_M]

Don't worry about the driver polarity - as long as you get the polarity from the speaker terminal to the amp correct, you are set. The speaker designer figured out the acoustic phase as part of the crossover design.

In my experience, phase is actually more sensitive the higher you go, because the wavelengths of the sound waves get shorter. You could miss the placement of a woofer by a foot with no real issues, but move the tweeter an inch from it's design distance from the mid and you wreck the crossover summation and phase. ... But you don't need to concern yourself with those details unless you plan to design your own crossover. Which is a lot of fun.