Dolby Pro Logic II & Cable hookups

[Jedi2016]

I asked about this in the Amp section, but it was geared more towards my reciever, and for all I know it may just be a cable thing..

Anyway. On the HT end, everything works fine.. the DVD player (Panasonic A110) is connected to the reciever (Sony STR-K750P) via digital coax. DD, DTS, Stereo, Dolby Surround, everything works wonderfully. The reciever simply identifies the incoming signal and plays it back as it should.

But my Playstation 2, on the other hand, has some issues when it comes to surround effects through DPL2. It's connected only via the standard RCA stereo analog cables. I've been under the impression from various forums that this is okay, that DPL2 will still work from a stereo signal (the GameCube does it after all, and it has only stereo cables, no option for digital). However, the reciever never recognizes anything except a stereo signal, and when I manually set it to DPL2, the sound ends up very "tinny" by comparison to stereo, less than half of the LFE that's normally present. The same thing that would happen if I were to turn the subwoofer volume knob down. Granted, it does play back through all five speakers, but it no longer sounds as "rich" as it does through normal stereo.

Is this a problem in the reciever, with a lack of bass management for DPL2? Or am I limited by the analog cables? The PS2 has a port for digital optical I could hook up easily enough (at the cost of an optical cable, and those are typically not cheap). If I were to use the optical, do you think the reciever would then be able to properly identify different signals coming from the PS2? Stereo vs DPL2?

It can recognize Dolby signals from the DVD player, with it's digital connection. There's a display on the reciever that shows which speakers are being used, and with stereo signals, it varies depending on the source.. sometimes it's just the front speakers highlighted (on old movies, like the classic Dracula I recently got with my Van Helsing DVD), and sometimes it shows "phantom" rear channels, the boxes active, but without the "SR/SL" text (like on the Firefly DVDs), where it's playing Dolby Surround from a 2-channel input (I'm thinking that, in theory, this is what a DPL2 signal should look like). And, of course, all the boxes are fully lit up with text and everything when it's reading a 5.1 source like Dolby Digital or DTS.

The DPL2 presets look different, though, when I manually set them for games. Normally it displays standard stereo, with nothing on the rear channels. With standard DPL, it displays the "phantom" rear channels, and on DPL2, it displays what appears to be full 5.1 (all speakers fully lit).

While it's not exactly a "home theater" question, it is an "entertainment system" question. I don't even have cable here, so all my time in front of the TV is split between DVDs and video games. And more and more games on the PS2 support DPL2, which I'm not really able to use effectively because of the difference in overall sound quality.

Anybody with experience hooking up a PS2 to a surround system could be most helpful. Google hasn't been much help, since it only seems to find various Dolby FAQs, which mostly tout how great Dolby is rather than offering advice for problems. Is there a setting I'm missing somewhere? Do I need a digital cable? Or am I just screwed by my reciever's lack of DPL bass management?

 

[MDS]

I suspect that the reason you feel that the sound is 'tinny' is because you are not getting the LFE (assuming the game actually has content on the LFE channel).

When you use the 2 channel analog cables, the player will downmix DD 5.1 to 2 channel analog. The receiver sees this 2 channel analog signal and then applies PLII to turn it into 5.1. Note that here the .1 simply refers to the subwoofer - NOT the Low Frequency Effects. If the original DD 5.1 mix on the disc contained content in the LFE channel, it will be discarded when the player downmixes to 2 channel. PLII does apply bass management and it should be working fine in that it will send bass below the cross over frequency (from any speakers marked 'small') to the sub.

Now, if you were to use an optical cable from the PS/2 (and I've read that there is a setting in the ps/2 menu that you must set to tell it to use digital out), then the entire 5.1 mix, including LFE if present, will be sent to the receiver for decoding and you will get bass from the small speakers plus the LFE.

Optical cables need not be expensive. The Monster Standard THX optical cables are $20 at BB and CC. Acoustic Research and Radio Shack cables are half that and will work just as well.

 

[Jedi2016]

Well, it's not a 5.1 mix, see.. it's only two-channel. The PS2 doesn't support in-game DD5.1 (it does support in-game DTS, but only a handful of games have it, and I don't own any of them). But quite a few games do have Pro Logic II. It just doesn't sound very good compared to stereo.

Is it possible my reciever is misinterpreting the DPL2 signal through analog? That it might be able to properly recognize it if it were digital? After all, it does auto-select the DVD signals, which are digital.

The games don't have LFE as a 0.1 channel, but it does have full dynamic range. When it uses normal stereo, the reciever is using three speakers.. left/right/'woofer, just like it does for everything else (TV, CDs, etc), in order to get the right sound. The 'woofer just gets really quiet when I switch over to DPL2, is all. Not completely off, there's still some bass, just not as much as with stereo.

 

[MDS]

PLII does not exist on a disc. What they probably mean when they say the game supports PLII is that the audio has been Dolby Surround encoded (and flagged as such). That means that the side channels have been matrix encoded into the left and right channels and the decoder will extract them. The center channel info is still created by taking the in-phase signals from the left and right channels and summing to mono.

Does this particular game say that it is PLII enabled? Is it DD 2.0? If it is DD and you use the analog outs, the surround encoding flags are lost and the PLII decoder will be doing the same thing it would do if you sent it an analog signal from your cable box; ie guessing what information goes where.

Analog 2 channel -> 5.1 surround will sound different than if you preserve the digital signal all the way to the receiver. I use coax digital from my cable box and it has no problem turning DD 2.0 broadcasts into 5.1, with the subwoofer. You said the lights show 5.1, so I assume you do have it in PLII mode, and not Stereo.

 

[Jedi2016]

Well, the one game I have with DPL2, Burnout 3, simply says "Dolby Pro Logic II".. no mention of Digital or Surround.

The upcoming game Gran Turismo 4, on the other hand, lists both "Dolby Digital Pro Logic II" and "Dolby Surround Pro Logic II" (although the website is in Japanese, these two Dolby logos are quite clear).

So in order to enjoy true "Dolby Surround" requires a digital output?

I just checked out my Firefly DVDs, they're listed as "Dolby Digital" and "Dolby Surround", and the audio is two-channel, split into three+2 (with the rear speakers showing up as "phantom" boxes, since there's not actually a discrete signal for them). I tried switching to stereo to see what the sound difference was on the DVDs, but I don't think I can.. hehe. The only way to force it into stereo mode for an incoming digital signal is to select "2ch stereo", which cuts out the 'woofer altogether (and sounds no better than those teeny speakers on the TV itself.. hehe). But the incoming signal was identified as Dolby Digital, and decoded with Dolby Pro Logic automatically.

It's starting to look like I'm going to need an optical cable... any suggestions for a good one to look for? I've got a Best Buy I use for all my electronics stuff (still new to the area, so not sure where anything else is just yet).

 

[MDS]

For an optical cable at Best Buy, you can get Acoustic Research or the Monster Standard THX. Monster is more pricey as you get into longer lengths. Either will work just fine.

Regardless of this issue you are having, I would recommend you use the digital out. It gives you far more options and is in general 'better'.

All these surround formats and decoders can get confusing, so here's a short review (concentrating on Dolby Digital (DD); same principles apply to DTS, but different decoders are used):

Dolby Digital
Anywhere from 1 to 5 channels plus .1 (LFE). 2.0 and 5.1 are the most common although occasionally you see 3.1 or 5.0. You MUST use a digital connection, either optical or coax, to get the bitstream to the receiver for decoding.

ProLogic
Older 4 channel form (R,L,C, RS/LS play the same mono content so its really only 4.0). Works on Dolby Surround encoded tracks and non-surround encoded tracks. Difference being that the surround encoded tracks have specific surround informatin matrixed into the L/R channels so when the decoder de-matrixes that channel it will get exactly what the engineer put there; compared to non-surround encoded tracks where it intelligently guesses what sounds to send to the surrounds. (it takes the out-of-phase; ie non-correlated info from the L/R and sends it to the surrounds.)

ProLogic II
Works on DD 2.0 or Analog 2 channel signals and turns it into 5.1. If the DD 2.0 track is surround encoded, the decoder will use the meta-data embedded in the bitstream to steer the sounds to each respective channel. If the signal is analog, it will intelligently guess, just like ProLogic, although it is more sophisticated and produces 5.1, instead of 4.0.

ProLogic IIx
Same deal as PLII, but can convert to 6.1 or 7.1 for the cases where PLII only converts to 5.1. Additionally can convert DD 5.1 to 6.1 or 7.1.

The key thing is to distinguish between surround formats and surround decoders. Dolby Digital and DTS are surround encoding formats (which naturally use a DD decoder). PLII is a matrix decoder.

If using a digital connection and the format on the disc is:
1. DD 5.1, then you can play it in 5.1 or stereo. Most receivers will keep the sub active for stereo mode.
2. DD 2.0, then you can play it in stereo or apply a decoder like PLII to turn it into 5.1.

With a digital connection, the bitstream and all of its meta-data arrive at the receiver and the decoder can use that meta-data to precisely steer the sounds to the right speakers. Because the signal arrives digitally, the receiver can then apply its bass managment settings to route the bass to the subwoofer.

If instead you use an analog connection from the player to the receiver:
1. The player downmixes to 2 channel analog - regardless of whether the format on the disc is DD 5.1, DD 2.0, or PCM (like a CD). The receiver can then apply PLII to turn it back into 5.1 surround, but its not quite the same because all of the meta-data from the DD bitstream is gone and it is back to applying its intelligent guessing algorithm.

So you want to use a digital connection if at all possible. It's possible that your receiver does not digitize analog inputs and apply bass managment and that is why you feel the bass is lower than when you play a dvd using an optical connection. Of course, you really need to compare apples to apples and play the same disc in both scenarios to be sure.

 

[Jedi2016]

Ah-HA! Yep, there it is... the meta-data that tells my reciever what to do with the sound it's getting... So right now, it's just guessing.. doing what it can with an analog 2-channel signal.

Anonymous (whoever you are.. lol), you've been a great help, and I thank you. Methinks I'm off to Best Buy now. I'll report back with the results once I've had a chance to compare the digital/analog sounds.

 

[MDS]

I'm just your friendly neighborhood computer geek (software engineer when I want to feel important ) that's also very much into digital audio.

 

[Jedi2016]

Well, I've got some mixed results.. on the one hand, there's still some loss of LFE in DPL2 mode (which I still have to manually select.. the reciever still doesn't recognize the incoming signal, even through digital). But on the flip side, the surround works, and works very well. Although to be honest, I never tested this particular game on analog (Medal of Honor: Frontline). But in the short test I did just now, one of the other characters, at the start of a mission, walks around a bit while I walk forward, talking the whole time. His voice started out in front, worked it's way left until it was coming soley from the rear speakers, then around the right side until he was in front of me again. Quite impressive. Now, if I could just figure out this damn LFE issue, I'll be golden.. hehe.

Maybe I've got it backwards? Is it possible that the normal stereo signal has too much bass? And I'm hearing it closer to reality through DPL2? I mean, aside from the drop in bass compared to stereo, the DPL2 sounds fantastic, as described above, really immersive, especially for a FPS like Medal of Honor.

 

[MDS]

There is no LFE track on a 2 channel recording. If your receiver doesn't automatically switch to PLII, that's a settings issue with the receiver.

Most receivers just remember the last setting, perhaps yours does not. I leave mine set to PLII Music. If I play a DD 5.1 track from a DVD or from cable, it automatically uses the DD decoder. If it receives a DD 2.0 signal, it automatically switches to the PLII Music decoder.

How do you have your speakers configured? Usually they should all be set to small, with a reasonable cross over frequency like 80Hz. If you have any speakers set to large, they will get the bass for their channel and likely not sound as powerful as sending the bass to the subwoofer unless they are really large floor standers that can reach way down low.

 

[Jedi2016]

I noticed this evening the lack of LFE on the DPL.. I saw the "LFE" light up on a DVD and realized that the games were all missing it.. hehe.

Normally, the reciever is set on "Auto", and it just interprets whatever's fed to it, as long as the incoming signal is original-digital (hey, that rhymes..). I think the problem actually lies with the PS2... as the first of the next-generation systems, it's missing the ability to encode Dolby Digital in-game, in any form, 2.0 or otherwise. The signal it exports, even through the optical cable, is still only PCM, according to the reciever when it starts playing (reads "PCM 48KHz", where it displays what the signal is.. DTS, DD5.1 for DVDs, etc). Chalk it up to an old system, I guess. So the reciever sees only the PCM, there's no digital data telling it what the signal is, so it assumes two-channel because that's all it's recieving. I just push the selection button to get it over to PLII MOV. PLII MUS yields better low-end, but it spreads the sound out more, rather than directing it to the specific speakers. So MUS sounds "better", while MOV sounds more "real", since the audio is more immersive. And yes, it auto-selects something else if it recieves a digital signal with the proper encoding (like a DVD).

All the speakers are indeed set to small.. it defaulted to that (since the HT set included them), and I haven't touched it. I'll see if I can find a setting for the crossover, but I'm not sure if it has one.

At this point I think I'm willing to just let it rest.. I mean, the PLII does sound good, especially when it's turned up a bit, it just doesn't have quite as much "oomph" like it does on stereo. Which, in a way, might be a good thing.. I can turn it up louder and enjoy the ambience more without pissing off the neighbors.. hehe.