Axiom Home Page Forums General Discussion Home Theater Which Speaker for Heights M2 or Qs8

Ok. I know most movies still only use 5.1. So how would getting height speakers help? Or does it do it by just repeating the sound from the fronts?

Dolby works their magic to pull ambient sounds from the front channels to the height speakers. For more on how exactly they do this ask Clubneon. If anyone here know's how they do it, he does.

Uh oh, I've been called upon, yet don't know the answer. Up to Prologic IIx, Dolby's processing has been pretty straight forward. They just look at the phase/amplitude differential between a pair of speakers (the front when making 4/5.1 from 2.0, or the surrounds when making 7.1 from 5.1), and steer the out-of-phase (surround), or completely in phase but with differing amplitude (center/rear) to where it should be heard. (Prologic II did add amplitude checking to the phased extraction to create 5 channels instead of the 4 from the older Prologic.)

As for IIz, I can only guess. Once I get to hear a setup, I might be able to refine this guess a little more. But I'm guessing they're looking for similarly phased information in more than a pair of speakers. Like in the mains and the surrounds of a 5.1 signal. Something like that would mean that the sound is coming from all around the listener, and would give the impression that it's up above their head. So moving it to the height channel, would be improve that impression.

I'd say that's about as good an answer as you're gonna get.

Yeah, Chris; as far as is known, Dolby hasn't provided precise details as to the DPLIIz processing for the height speakers. What has been said is that the front channels in 5.1 source material aren't affected and that the side surround channels are processed. It may be that just as DPLII extracts out-of-phase material from the front channels in 2-channel sources and sends it to side surrounds, DPLIIz extracts out-of-phase material in the discrete 5.1 side channels and sends it to the height speakers. The rationale would be that the phase difference in the side channels results from the sound arriving from a different height. Of course, it may be more complex than this.

That makes sense. Along with in-phase, but differing amplitudes still being extracted for the rear channels for people running 9.1.