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Center channel volume differences

3K views 10 replies 2 participants last post by  giovanni 
#1 ·
Hello, I am hoping for some info on the problem I am having.....

The volume that I get out of the center channel speaker varies depending on what television station I am watching, and also what program is on at the time. For example: during Hockey Night in Canada broadcast (CBC) the anouncer's voices are quite low but the front speakers sound like they are a better level, when a commercial comes I have to turn it down because it is too loud. Similar problem if I change channels, some are quite louder than others. I have juggled back and forth with the speaker levels within the processor but the problem still occurs.

I have gone through other setups within the processor but cannot find a solution. From what I can tell it does not have any "Audissey" or similar setup.

Here is my setup:

Anthem AVR20 Surround Sound Processor
Elan D12 Amp
Paradigm Monitor 7 vs6 Fronts
Paradigm CC-190v6 center channel
Paradigm ADP 190v6 surrounds
 
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#2 ·
The centre speaker is not used on channels that sometimes broadcast what I call "improperly encoded DD5.1". Although these channels send a DD5.1 signal, only the Left-Front & Right-Front speakers should be active on some programming and you shouldn't be hearing anything from the centre speaker (or the surround speakers), unless you have "crosstalk" or are on the incorrect decoding option, which should probably be Dolby Pro Logic II setting, which changes to DD5.1 when it receives a DD5.1 signal. The advertisements associated with these "improperly encoded programmes", are often properly encoded DD5.1, hence the proper audio from those ads. See Note 1 of the FAQ:

http://www.digitalhome.ca/forum/30-57s-home-theatre-faqs/17870-faq-whats-available-dd5-1-a.html

Edit: If you're trying to decode a DD5.1 (or DD2.0) signal with another (incorrect) decoder setting, say "All-Channel Surround" or "5-Ch Surround" or whatever it may be called on your processor, this could result in the improper levels that you encounter as it's trying to "force" a signal to the centre and surround speakers when nothing should be fed to them.
 
#3 ·
I understand what you are saying, but why is it that there does seem to be a signal to the center channel only very low.

I don't think the problem I am experiencing is one that there is no signal to the center channel. It is there, only very low. Then blasts when a commercial comes on.
 
#4 ·
I suspect it's low either because there is crosstalk in your equipment that should not be there, or because the decoder is not segregating the incoming signal the way it should. What decoding type are you using for incoming DD2.0 signals that are present on all SD channels? It should be DPLII. As I stated earlier, on channels like CBC when it's sending "improperly encoded" DD5.1, there should be absolutely no audio coming from the centre or surround speakers, only from the LF & RF.

Of course, much of the programming on CBC is properly encoded DD5.1 and the sound should be fine when that signal is present. Unfortunately, there is no way to tell whether one or the other is the case other than by listening, because the processor or AVR will "show" DD5.1 on the display regardless.
 
#5 ·
When I tune to CBC the processor automatically turns to 5.1.

I am assuming this is what it is supposed to do.

The only thing I can change is the "THX" factor. If I put that on the sound will drop in all the speakers, but when I turn up the volume I notice that the level differences in the center channel are still noticeable.
 
#6 ·
When I tune to CBC the processor automatically turns to 5.1. I am assuming this is what it is supposed to do.
Yes, but what does the processor do when on a DD2.0 channel, like an SD channel? Change to a channel like CP24? Is it now showing DPLII? What I'm wondering about is if the incoming DD5.1 signal is being "modified" by say "5-ch Surround", or some similar (background) decoding. Most processors do not "modify" incoming DD5.1 signals as you noticed in that you can only change to "THX".

What is the source of your TV channel audio - is it a set top box, TV, other?

You may also want to check your speaker wiring. When you run a speaker test do all the speakers come on properly at similar volumes - LF, C, RF, LS, RS, etc?

http://www.digitalhome.ca/forum/30-57s-home-theatre-faqs/19694-faq-things-check-first.html
 
#7 ·
I am using a Bell 9242 box. I also have a rooftop antenna for local HD OTA connected to it.

As I scan through the channels the Anthem processor changes from these options:

DD 5.1

Dolby Digital PLIIx

Digital Dolby

DPLII

I can add the THX on any of these, but these are the ones that come up. The center channel volume is greatest on the DD5.1, but almost non exisitent on others but it is there.

OTA is mostly DD5.1.
 
#8 ·
I assume that the 9242 is set to output DD and not PCM in the settings. The 9242 is quite old, perhaps there is an issue with it?

You could try feeding the antenna feed to the ATSC tuner of the TV (assuming it has one) and then set the TV audio out to "external speakers" via the optical output and see if you notice any difference with that setup (if that's not too difficult to do).

Perhaps there is some issue with the Anthem - I know they can be pretty finicky to set up properly. Did you run the test tones as I suggested in my earlier post? I assume the Anthem has a set of test tones that can be run to check the volume of each speaker...
 
#9 ·
The 9242 was set to Digital Dolby/PCM. I changed it to Digital Dolby.

I went through the setup menu on the Anthem Processor. All of the speaker levels are the same at +5. I did the sound test and they all sound very similar.

There was no difference in the center channel volumes after the change.

I am assuming it has to do with what you mentioned earlier, that not all broadcasts are the same. I just find it very annoying that as I scan through channels to find what to watch the volume is all over the place.
 
#10 ·
Thanks for the feedback. I've run out of suggestions, but here are some tests that you may wish to try as you have time.

1. Tune to a music channel like Stingray that has singers/groups on it - something like Adult Alternative. This should send a DD2.0 signal to the processor. Try various decoder settings and see what happens.

A) Try "Stereo". You should get sound from the LF & RF and nothing out the other speakers.
B) Try "5-Ch Surround" or whatever a similar decoder setting is called. This should send identical audio to all of your speakers.
C) Try "DPLII Cinema/Movie". This should have most of the vocals out the centre speaker, with the other 4 speakers active, but not as much typically from the surrounds.
D) Try "DPLII Music". This should "spill" some of the vocals to the LF & RF speakers, with the surrounds slightly active, depending on the sound material.

The above effects may depend a bit on the nature of the music.

2. Try the same on an SD channel like CP24. The effects should be similar, however, with a channel that has mostly dialogue like CP24, the audio should mostly come from the centre speaker. When there are commercials, you may hear more audio out the other speakers.

3. Try CBC News Network HD. This should send a DD5.1 signal, but it should be "improperly encoded" and send audio only to the LF & RF speakers. Nothing should be coming out the other three speakers. (Before switching to that channel tune to an SD channel and set the decoder to DPLII Cinema/Movie). This should be similar to what happens on CBC and PBS when they are sending an "improperly encoded" audio stream via DD5.1. Some PBS channels may send DD2.0, in which case the incoming signal is DD2.0 and decoded properly by DPLII.

4. Try any of the other HD channels and you should get proper DD5.1 audio...
 
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