Does DD-EX remove out-of-phase sound altogether? (1 Viewer)

[Jeremy Anderson]

Posted this in another area with no response, so let's try it here. For the hell of it, I played the THX audio tests on Disney's Lilo And Stitch tonight on my Onkyo SR600 receiver. Here's my beef:

On the phase tests, it says the in-phase sound for the surrounds should come from the rear center channel... which it does. So far, so good. However, it also says that the out-of-phase sound for the surrounds should come from the right and left surrounds in an EX system. During the out-of-phase portion, I get a barely audible hiss instead of sound from the left and right surrounds, almost as if the receiver was cancelling out out-of-phase data during processing.

Checked it out with Avia's speaker phase tests with the same results. So is out-of-phase surround data supposed to be removed by the EX processing, or is the Onkyo faulty in some way? It would seem to me that with the THX test saying that out-of-phase data should come from the side surrounds and it not actually working that way, perhaps there is a problem with the way this unit decodes DD-EX. Anyone have any ideas?

 

[Vince Maskeeper]

Well technically, out of pahse sound in the rear could be extracted into another channel (this is how surround is matrixed into pro logic tracks)--- Dolby has often discussed adding a "voice of god" channel overhead using a surround channel extracted from stereo surrounds...

So, I assume your gear is doing what it's supposed to do. I never really thought too much about how the current ex decoding would handle such things-- but that sounds logical enough. I would just turn off EX processing for the phase test anyway- as the in phase sounds will come from rear center with EX on, and they shouldn't.

-Vince

 

[GregLee]

Since the test is supposed to give out of phase sound from the surrounds and you don't get that sound, I don't see how to avoid the conclusion that something is wrong with the receiver or the way you have it set up. Maybe you have to use some receiver control to tell it to use DD EX.

 

[Jeremy Anderson]

Vince, I'm not worried so much about the phase test itself, because I know the phase is correct for my speakers. The question is whether the decoder is performing correctly with EX or DTS-ES material.

In other words, if it's removing out-of-phase material in EX mode with the THX-EX test (which clearly states that out-of-phase material should come from the left and right surrounds in an EX system), then isn't it removing out-of-phase sound when watching movies?

Basically, I'd like to know if this is inherent to all EX receivers or if only the Onkyo does this. If it's all of them, no worries. If it's just the Onkyo, they've got some 'splainin' to do.

 

[Vince Maskeeper]

Where is this clearly stated? The only time I've read anything mentioned in terms of out of phase sounds and EX decoding, it was in ref to a possible "voice of god channel" in dolby soundtracks.

-Vince

 

[Jeremy Anderson]

Vince, I was referring to the THX Optimode tests for phase (specifically on Lilo & Stitch, but I've tried it on several discs). During the out-of-phase test for the L&R surrounds, it says in-phase should come from the center surround in an EX setup and out-of-phase sound should come from the left and right surrounds. But during that test, I get a barely audible hiss instead of a full out-of-phase sound from the surrounds.

This isn't so much that I have a problem with the way my system sounds as just a point of curiosity as to whether EX decoding is SUPPOSED to remove out-of-phase sound. It would seem to me that removing that data from the surrounds makes you miss out on some of the intended sound. Unless, of course, it's SUPPOSED to be that way, which is what I don't know.

 

[JohnnyG]

EX is supposed to work like a Pro-Logic center channel decoder, which does NOT touch phase at all. Basically, sounds that are IN-PHASE and equal volume in both channels are extracted and re-directed to the center channel.

I can not think of any reason why an EX decoder would 'play with' phase in the surround channels.

 

[Jeremy Anderson]

Exactly! Which is why I'm thinking the Onkyo may have a problem with the DD-EX decoding. But I don't want to cry wolf unless I can prove there actually is a problem. Before I make a big deal over it, I'd like to know:
A) If this is indeed a "problem".
B) If other people with the SR600 have this problem (or is it just that my unit is faulty).
C) If other Onkyo models have this problem.
D) If other brands exhibit this same behavior.
E) If there's any way to find out if DTS-ES has a similar problem on this receiver (i.e. are there any test discs with phase tests in DTS?).

 

[GregLee]

JohnnyG
EX is supposed to work like a Pro-Logic center channel decoder, which does NOT touch phase at all. Basically, sounds that are IN-PHASE and equal volume in both channels are extracted and re-directed to the center channel.

I can not think of any reason why an EX decoder would 'play with' phase in the surround channels.

But then the signal playing through the back surround is subtracted from the signals going to the side surrounds, as I understand it. Which is why with DD EX active, out-of-phase info should be coming from the side surrounds.

 

[Jeremy Anderson]

That's my understanding of the way DD-EX is SUPPOSED to work, Greg. That's why I'm curious as to why my Onkyo SR600 is just throwing away out-of-phase data in the surrounds. What's more interesting is this: during the out-of-phase sound test, all you hear is a slight hiss, stronger in the left surround (verified with a SPL meter at 1 ft). Maybe we can get someone from Dolby to comment, because I just don't think DD-EX is supposed to work this way. And if it isn't, then Onkyo is putting out faulty product.

 

[Vince Maskeeper]

Jeremy,

My advice would be a more direct approach. I post something like this in the receivers/processor area:




I'd post that, and I'd be eager to see the results.

 

[Jeremy Anderson]

Good call, Vince. I like the way you phrased it so much I'm gonna' cut-n-paste it.

 

[Jeremy Anderson]

So far on this and other forums, I've heard from owners of Sony, Aragon, Pioneer, Yamaha, and Sunfire brand 6.1/7.1 receivers. All of the above send the out-of-phase surround test to the left and right surrounds. Obviously, the normal behavior for EX decoding is to pass out-of-phase sound to those speakers. I e-mailed Dolby Labs to verify that this is the correct behavior.

However, I have yet to hear from anyone with another Onkyo to verify whether this is just my unit or the entire line. We'll have to wait and see.

 

[Jeremy Anderson]

Update: Someone on another forum with the same receiver (SR600) posted their results and said that the out-of-phase tone is correctly being passed to their left and right surrounds. So it's looking like maybe it's just my unit. I suppose I'll have to call and talk to Onkyo about this.

 

[JohnnyG]

Does the unit have a processor reset function? If so, try that. Otherwise, re-check all your settings and if you're not exactly sure what a particular function does, toggle it and try the test again.

 

[Jeremy Anderson]

I called and spoke with someone at Onkyo, who put me on hold to run the SW:AOTC THX Optimode test on one of their units. After 20 minutes of listening to them in the background saying "Hmmm..." and "S#!t!" they came back on and said "Uhm, can we get your number and call you back after we've done some more testing?"

So maybe this isn't an isolated problem. I guess I'll just have to wait and see. Hopefully it's something Onkyo can fix.

 

[Jeremy Anderson]

Update:
I had e-mailed Dolby asking whether it was normal for this to happen and got the following response.

"From what you describe, the out-of-phase signal is indeed being discarded with the out-of-phase test signals. While Dolby recommends that Dolby EX decoders be made so this does not happen, it should not be noticeable on normal 5.1 or EX encoded program material. We will discuss this matter with Onkyo. Thank you for bringing it to our attention."

Spoke with someone at Onkyo again today and again was told they'd have to call me back. Blech.

 

[Jeremy Anderson]

FINALLY, I got in touch with one of the service managers at Onkyo. Both of the units they tested in their lab passed the left and right surrounds correctly. They told me how to reset the receiver to factory defaults, and if that doesn't work they want to look at it themselves and they'll have it fixed or replaced within a week. Hopefully when I get home the reset thing will work, but if not, at least they're handling the return fairly quickly.

 

[JeremyFr]

wow I consider myself an enthusiasts but I dont think I would have ever noticed something like that I was gonna go home and check my Yamaha for this until I read the rest of the post. I'm glad you got your problem figured out that would be frustrating to not know why it was doing that. also I'm very impressed with the response you got from Dolby seems like they're really on top of things and more than willing to help "the little guy" with problems I respect any company like that.

 

[Jeremy Anderson]

UPDATE:
I took my SR600 back to Circuit City and got a new one, thinking maybe this one was just faulty. Alas, the same thing happens. So now, I guess I'm going to send this brand new unit to Onkyo for testing.