Surrounds and Fronts Weak Using Pro-Logic with TV (1 Viewer)

[Jeff Barnett]

First off, heres my setup

Panasonic Tau 27" TV

Pioneer VSX-D509S Receiver

My surround setup works great with DVDs and true 5.1/DTS, but when I turn the receiver to the TV input, it seems all I get is the center channel and a little bit of subwoofer. The fronts and surrounds are outputting, just not very much. The only way I can get them to have any presence is to set the receiver to stereo mode (L&R only), which doesn't really sound good to me. Whenever ProLogic is engaged (my best option with standard cable TV) the fronts and surrounds just fade away. I don't want to reset the channel levels on the receiver, because that will mess up the great sound I have with DVDs. Is there a possibility I don't have something engaged on the TV that should be? Is there a receiver setting I can try? Any help is greatly appreciated.

Jeff

 

[Greg Robertson]

Have you verified if your tv is outputting stereo or mono signals. I know on my sony, there's a remote button that changes from mono to stereo to SAP. That sounds kinda like what happens when you feed a mono signal to a pro-logic decoder.

 

[Jeff Barnett]

The TV is set to stereo, thats all I can vouch for. The choices there are just like your Sony, and of the three, it is set to stereo.

BTW, I just chekced again, and the surrounds have NO output.

Thoughts?

 

[Luke_Y]

Jeff, I'll explain what hapened to me as you may be having the same problem.

At one point the way my system was set up I had the cable hooked up to the TV via the coax out of the cable box. That way when I just wanted to watch news ect. I wouldn't have to power up the rest of the system, I could just listen through the TV speakers.

Well on my TV when you push the button on the remote for the "display" it would show the chan and also indicate "ST" for when it was receiving a stereo signal.

Well one day I noticed the "ST" was gone. I called and a cable guy came out and showed me how to use a setting in one of the cable box setup menus to "match the volume with my TV" and what do you know the "ST" was back and I was geting a stereo signal again. This occured once again when the digital cable box "updated" and reset, the setup menu was now GONE with the new update so I couldn't make the fix. I called and was told the setup menu was no longer required- go figure.

Anyway I digress, my point is my receiver was not affected by this becuase I was using the RCA audio outputs direct from the cable box into the receiver for watching TV through the system.

If I had been using the RCA audio out from my TV into my receiver I would have lost stereo signal to the receiver as well when I lost it to the TV. IE no stereo signal into the TV on the coax input--no stereo signal out of the TV to the receiver via the RCA audio outs on the TV.

I dont know why the stereo signal out of the cable box was only affected on the coax out and not the RCA audio out.

Hope this might help you some.

 

[Chuck Kent]

Even if a TV is getting a stereo signal, the Pro Logic decoder (no matter whether it's original DPL or the newer DPL II) is only as good as the signal that's fed to it.

IOW, if the original signal has little or no separation, or if the TV's stereo decoder is not doing the best job at creating the separation that's in the program, then the result is quite often not much better than plain old mono.

In my system, I seldom use the TV as the tuner source. I have found that VCR tuners seem to offer better separation and have lower background noise.

 

[MarkO]

Chuck has a point.I used to have the same problem with my Television brodcasts. Eveything seemed to migrate to the center channel. What was surprising was after I upgraded my reciever, (a pre/pro in my case), the seperation between channels was greatly improved. Im not saying you have to have a pre/pro or spend big bucks to get the improvement, but what is possible is that some prologic decoders are better than others and may dig a little deeper into the signal to get the added seperation in a low quality signal that some Television tunners put out.

 

[Jeff Barnett]

Those are some interesting points. I too would like to be able to use the TV speakers sometimes, and run it through the receiver sometimes, but I don't use a cable box. Also, the TV will only output audio when the TV speakers are turned off. Anyway, that is another quam in itself.

I don't really know how to check the quality of the stereo signal in and out of the TV, which would eliminate the receiver as the source of the problem, if it is. I might try running it through the VCR, although I don't really want to stick with that because then I would have to operate 3 separate devices just to watch TV in DPL. That might tell me what the problem is, though. I run my coax from the wall to a splitter, with each output of the splitter going to the TV and VCR respectively. Could the splitter be my problem?

Update: I checked the surrounds last night after turning on the "loudness" feature of my receiver, and there was SOME output. The speakers sounded fine, the volume was just insanely low compared to the center channel. I'm still perplexed, and it looks like it will be a hassle to get it the way I want it.

 

[John Royster]

I was under the impression that prologic is only good if you are listening to a prologic source. If the two channel sound is not encoded with prologic information then what good is the decoder doing? guessing?
Then again, I might not have any idea what I'm talking about

 

[Jeff Barnett]

I might be off my rocker as well, but I thought that ProLogic decoders simply mixed a thrid mono channel from the L&R channels given to them. I didn't think it was like DD in that a "ProLogic signal" must be given to it.

 

[John Garcia]

Sort of. There are different versions of PL material available, and it IS specially encoded with information for the surrounds. Pro-logic CAN enhance stereo music, but that is not its purpose.

As stated, just because you have a stereo signal, does not mean you will hear clear sound from the center/surround.

 

[Rick_Brown]

Jeff, have you tried playing an audio CD through prologic (use your DVD player if no CD player)? Any audio CD will have lots of stereo information on it, so you could play one to see if you get much action and volume out of the surrounds (I do). If CD's sound fine, then your TV signal/progams must be the problem.

 

[jacek p]

Jeff,

I confirm than some TV programs (news, documentaries, etc.) have mostly mono-like signal, which Pro-logic sends to center.

Another issue is that Pro-logic is very limeted. Try Pro-logic II (especially PLII music), you will see a lot of improvement on conventional programming and stereo signals (CD, tuner, etc.) as well.

Cheers,

 

[Jeff Barnett]

Thanks guys. I'll try an audio CD through the setup tonight and see how it goes.

Jeff

 

[Jimmy P]

I have a Pro Scan and it has 2 types of RCA audio out jacks One set has variable audio out,when i used this output my receiver did not funtion properly,the audio was faint just as you described.

The other output has fixed audio out,the fixed audio out has a higher level output,and my receiver would function correctly.

The variable output was to enable use of the tv's remote for volume control of the receiver through the tv.

Does the Panasonic have multiple audio out jacks,in particular the variable variety?

 

[Ken Chan]

I was under the impression that prologic is only good if you are listening to a prologic source. If the two channel sound is not encoded with prologic information then what good is the decoder doing? guessing?

First, there is no such thing as "encoded in Pro Logic". Such material is encoded in Dolby Surround. Most TV shows are nowadays; they even have the logo at the end (and that logo says Dolby Surround).
Pro Logic signifies the type of decoder. In the early days, there were non-Pro Logic decoders, that gave you only the left, right, and mono surround. Then Pro Logic decoders became available. When decoding the same Dolby Surround material, they also extracted the center channel, which was always "there". All Dolby Surround decoders nowadays are Pro Logic decoders -- except for Pro Logic II, which is an even better decoder for the same Dolby Surround material.
One of the tricks with Dolby Surround is that it is a totally valid two-channel signal. There's no extra stuff; it's just the way the material is encoded. For example, if the same signal is present in both left and right, it's actually placed in the center by the decoder.
Now, a non-Dolby Surround signal might happen to have the same thing in both left and right, and if you play that with Pro Logic, you'll get that sound in the center, but that doesn't mean it was supposed to be that way. The result may be more "surroundy", but it's also likely to be wrong. So the decoder is no so much guessing, but rather using the cues that are there, because you told it to. In contrast, you can't play DTS with a Dolby Digital decoder, because there is extra stuff that makes a signal DTS or DD (besides being compressed/encoded in different ways), and when the decoder doesn't see it, it doesn't go any further.
Having said all that, most TV shows aren't that surroundy. The SciFi channel also seems above average, with their "This is SciFi" station ID and the Farscape swoosh you get after commercials. For the fronts, look for stuff that has different sounds in the left and right channels, like cars driving by, or the theme music for a show, or maybe the live music during late night shows.
//Ken

 

[John Royster]

Thanks for the info Ken!

 

[Dan Hitchman]

1) The station has to be broadcasting in stereo.

2) The program has to be in stereo or stereo surround (Dolby or some other matrix surround format).

3) MTS stereo for TV doesn't have the greatest stereo channel separation in the first place (about the same as FM radio), which can effect the quality of the ProLogic decoding in the first place.

Dan

 

[Jeff Barnett]

Some great info there, Ken. Thanks.
Jimmy, my TV has only one set of audio outputs, but you change it from variable to fixed in one of the TV menus. It is set to fixed.
Didn't get a chance to audition a music CD last night. :frowning:
Jeff

 

[Bill Kane]

Jeff,

I'm not so sure you have a "problem" when listening to TV in DPL and experiencing "weak" surround sound.

TV/Cable feed processed as DPL mixes the rears in mono. You aren't going to get "discrete" rear surround (DD 5.1) like DVDs, so TV DPL is inherently less evident in the rears and sometimes the L/R fronts too, as the Center picks up the main soundtrack.

Much depends on the source being broadcast, I've found. The only time this makes any difference to me is when I watch movies in my cable HBO/Cinemax/Showtime channels. Sometimes there is more info in the rears, but it usually pretty much just "whispers." Rears aren't spozed to be sound directional anyway. For the most part, they're for ambience, mounted above ear level and pointed somewhat into the room per Dolby Labs.

That said, I have recently switched to my Hi-Fi VCR as a TV tuner and hear a bump-up in sound clarity. PQ remains the same. I run the wall cable into my power center/surge suppresser because it's there, and out to the VCR RF IN. Then OUT to the TV's F-Connector antenna IN terminal.

TV RCA audio OUT goes to the amp's D-TV/LD input. VCR's RCA audio out goes to amp's corresponding inputs. VCR video goes to TV's EXT1 input. To view, I switch my rcvr to VCR1 and TV to EXT1 via remote. Except for watching DVDs in S-Video feed, I can now just leave it set here.

Since my TV has fixed audio, I set my TV VOLUME approx. half gain and turn the TV speakers OFF. Now I can stow the TV remote, all other picture settings being equal, calibrated via AVIA disc. (You can still revive the TV remote to turn the VOLUME back on -- LOWER IT FIRST -- and watch/listen directly to the TV).

This leaves my with TWO remotes: the VCR remote is programmable for the TV, a Mitsubishi. The VCR remote turns on the TV and VCR and changes channels. I still need the amp's remote for volume control and to switch between L/R Stereo mode sometimes and the DSPs. I WILL adjust the SUB level up from "reference" when I detect some better thump in a particular CableTV source program.

If you try this, try the TV's Variable Audio Output mode as well as the FIXED, to get the volume level set up most convenient for you; it's best, I think, to input the TV's full line audio into the receiver.

this is my take AICBC (And I Cud Be Corrected), hope it helps.