Dolby Pro Logic vs Dolby Digital?

[therock003]

I own an old Sony Hi-Fi that supports Dolby Pro Logic. I read that this was one step before Dolby Digital (AC3). But i still cant understand if this is really for surround sound environments, or if it is just a slight upgrade from stereophonic sound.

What's the best use i can get out of my Stereo that supports this format?

As far as i can see, it supports up to 6 speaks.2x Front/Rear/Center. I've got 7, i've also got the TOP one, and i'm also wondering how to connect the extra speaker...

[jagabo]

Prologic encodes a center channel and a rear channel via phase variations in a stereo signal. The four channels aren't 100 percent independent. If the receiver has two rear speaker connections both will get the same rear channel from the Prologic decoder.

Prologic II increases that to five channels, with two rear channels instead of one.

http://en.wikipedia.org/wiki/Dolby_Pro_Logic

[therock003]

I really need the help to set this up, so allow me to be more specific so i can get things going.

I read that Pro Logic is 4.0 instead of the usual 5.1.

-It seems the it doesnt have a channel for Woofer, and the surround channels is monophonic. So Am i Correct to assume that both surround (Rear Speakers) Output the same sound information, instead of SurroundLeft and SurroundRight?

-Another question that bothers me. Do the Center Speaker (Ground Speakers) opearate the same as well? Meaning they output same sound instead of different sounds for left and right? That must happen for 5.1 as well though not just Pro Logic.

-This is an Important question, i gather. How does the HiFi get its information of 4 separate channels? All i seem to find on the back is the usual white/red stereo inputs. So How can you feed Pro Logic Sound and get decoded correctly and drive the speakers?

-Windows Software. Is Windows support for on-the-fly downmix, from various audio formats to Dolby Pro Logic widely accepted? Or will i have to hassle to achieve this sound format?

As you can see, at the moment i dont own anything fancy, so i'm trying to get the best i can with what i've got.

EDIT: Thanx Jagabo for your response, you posted as i was already typing this. I have seen the wiki article already and based to my limited knowledge the questions i posted here, is what's on my mind, in order to get a firmer grasp on the matter. Could you pleae address them? Appreciate it

[jagabo]

I read that Pro Logic is 4.0 instead of the usual 5.1.

Yes.

-It seems the it doesnt have a channel for Woofer,

Yes. If the amp has a separate sub output it's simply the left and right channels added together and sent through a low pass filter.

and the surround channels is monophonic. So Am i Correct to assume that both surround (Rear Speakers) Output the same sound information, instead of SurroundLeft and SurroundRight?

Yes.

Do the Center Speaker (Ground Speakers) opearate the same as well?

Yes. They supply a top and bottom speaker so that the sound appears to be coming from the middle of the TV screen, rather than above or below it.

[therock003]

I Still dont get some things though. Mostly how is it supposed to get information from 4 different channels via a simple red/white cable?

So the Center speakers are placed right above and underneath the TV?

Here's what i got.



So the middle one must for center, but i only got one, So if i place it on top, i aint got nothing for bottom so the sound, will be like its coming from above the TV as you said. How do i solve this?

As for left and right i got 4 of what you see, on the picture. Although 2 of them are rated 8 Ohm/70Watt "SS-SR12" (see pic below) and the other two are rated 16 Ohm/20 Watt "SS-SR151". Which ones should i use as surround (rear) and which as front?



And finally i got 2 large groundspeakers, that at first i thought they were to be the center speakers, but now i understand that small top/bottom are supposed to be center...

So i'm still non-conclusive on the matter.

[KBeee]

Pro Logic is not 4 channels, it's closer to 3. It's stereo for the front, and out-of-phase signal for the rear which can impart a kinda pseudo surround sound, or with a carefully engineered stereo soundtrack some quite convincing rear effects. The 2 rear speakers each give the same sound, but by using 2 speakers at the rear, the rear sound stage is expanded.

You can get very similar results to Pro Logic just by wiring 4 speakers up in a Hafler arrangement, but you won't get separate volume control of the rear speakers, or the half-strength DolbyB noise reduction that Dolby Pro Logic gives you.

[jagabo]

I Still dont get some things though. Mostly how is it supposed to get information from 4 different channels via a simple red/white cable?

When the two channels are in phase the sound is routed to the center channel. When they 180 degrees out of phase the sound is routed to the rear.

So the Center speakers are placed right above and underneath the TV?

Here's what i got.


[Attachment 7309 - Click to enlarge]

So the middle one must for center, but i only got one, So if i place it on top, i aint got nothing for bottom so the sound, will be like its coming from above the TV as you said. How do i solve this?

If you only have one center channel speaker you have to put it above or below the TV screen (in movie theaters it is located behind the projection screen).

As for left and right i got 4 of what you see, on the picture. Although 2 of them are rated 8 Ohm/70Watt "SS-SR12" (see pic below) and the other two are rated 16 Ohm/20 Watt "SS-SR151". Which ones should i use as surround (rear) and which as front?

Use the 70 watt speakers in the front, the 20 watt speakers in the rear.

And finally i got 2 large groundspeakers

Two sub woofers? Placement of those isn't critical. It's difficult to tell what direction very low frequencies are coming from. Do they have inputs and outputs? If so, go from the receiver to the subs' inputs, then from the subs' outputs to the left and right speaker.

[therock003]

So Pro Logic isnt 4.0 or even 3.0, it's just Pseudo-Surround created by a stereo-source. Is this What matricized channels that i keep reading, means? The Fact, that Center and Rear are created from Phase Differentials?

If you only have one center channel speaker you have to put it above or below the TV screen (in movie theaters it is located behind the projection screen).

The HiFi allows for 2 of them but the packaging only had one. What if i place it behind the screen as well, facing the wall, so the sound gets refracted to the wall. Would that be wise, ot just hit and miss?

Use the 70 watt speakers in the front, the 20 watt speakers in the rear.

I thought that the rear ones needed the extra power, since the signal has totravel the greater distance from the HiFi source. How come the front get the 70 Watt Power?

Two sub woofers? Placement of those isn't critical. It's difficult to tell what direction very low frequencies are coming from. Do they have inputs and outputs? If so, go from the receiver to the subs' inputs, then from the subs' outputs to the left and right speaker.

I'm not sure if they're meant as subs. I'll post some picture of them as well, so you can take a look for yourself. Maybe i'm describing them wrong.

[jagabo]

So Pro Logic isnt 4.0 or even 3.0, it's just Pseudo-Surround created by a stereo-source. Is this What matricized channels that i keep reading, means? The Fact, that Center and Rear are created from Phase Differentials?

Yes. Basically the sound can be steered to the four channels but the four channels aren't independent. That is, you can't have four full bandwidth channels of sound at the same time.

If you only have one center channel speaker you have to put it above or below the TV screen (in movie theaters it is located behind the projection screen).

The HiFi allows for 2 of them but the packaging only had one. What if i place it behind the screen as well, facing the wall, so the sound gets refracted to the wall. Would that be wise, ot just hit and miss?

It would sound terrible. High frequencies don't bounce off walls very well. The sound would be muted. It's much better to have the speaker above or below but facing the viewer.

Use the 70 watt speakers in the front, the 20 watt speakers in the rear.

I thought that the rear ones needed the extra power, since the signal has totravel the greater distance from the HiFi source. How come the front get the 70 Watt Power?

Because that's where most of the sound will be.

[therock003]

Yes. Basically the sound can be steered to the four channels but the four channels aren't independent. That is, you can't have four full bandwidth channels of sound at the same time.

-I see. So it doesnt matter, if my source is mp3,ac3 or dts, it's all going to be downmixed to stereo before it travels to the HiFi system which in turn will deliver the sound to each speaker, that depends to one another to create the surround effect. Correct?

-My last serious question is this. Is this really better than having a simple 2.0 or 2.1 stereo setup, since this is nowhere near an independent surround setup?

It would sound terrible. High frequencies don't bounce off walls very well. The sound would be muted. It's much better to have the speaker above or below but facing the viewer.

Would you rather suggest i dont use the one that is solo, and use a pair of the small ones instead to have it properly up and down the TV set?

As for the ones i mentioned as ground speakers, i cannot get a picture online, but i found this manual. IT seems they are front/center and super woofer all in-one. They even have external connection for rear speakers. Could this may be prefereable?

I did find the manual though.

http://pdf.crse.com/manuals/3856457121.pdf

[yoda313]

Is this really better than having a simple 2.0 or 2.1 stereo setup, since this is nowhere near an independent surround setup?

Yes.

If you've never had surround sound before anything is better than nothing.

I started out with a surround amplifier add on that hooked up to a regular stereo amp. It wasn't much but it was enough to add to the experience (back in the vhs days). Then I migrated to dolby pro logic and it was more enveloping.

When I finally got my current dolby digital/dts 5.1 amp about 8 or 9 years ago and a dvd player the difference was amazing. The independent channels really make for a very engrossing movie.

Perhaps the biggest benefit is the bass. With prologic the bass is throughout the whole track. People talking, ambient noise, everything goes through the subwoofer giving it an unrealistic boost across the whole track.

With dolby digital and dts the independent center and sub channel make a world of difference. The Voices are perfectly centered and the lfe channel is doing what it is supposed to do while keeping the regular sound more natural without extra bass.

If you can swing it I'd suggest looking for a real 5.1 amp used if you can. I'm sure ebay has it but shipping might be prohibitively expensive.

I also would seriously consider a htib - home theater in a box. They can be limiting if you go super cheap with a built in dvd player and only dolby digital. Also if you go super cheap with a player built in they might not have any digital input (coax or fiber optic).

But the difference is worth it. Even on a underpowered htib the difference should make it worth it.

edit - even the most basic dolby surround mode (the first gen dolby) is more immersive. Having a home theater of any description is a lot of fun. Simply having a space ship fly around you or hearing the echo of a gun shot is a blast.

Stripped down to its basic element surround sound is just having speakers behind you. Heck even matrixed hall surround with the same front stereo duplicated in the back is kind of fun albeit a little unnerving if not done correctly.

I'm curious - if you already have the equipment why haven't you hooked it up already? As long as you have some time test it out. Its fun to do.

Also I wouldn't be too concerned about proper speaker placement. There is no right or wrong to set up a home theater system. It is for your enjoyment. If something doesn't sound right to you move it around. Not everyone has a perfect square room with sound absorbing panels and properly mounted rear and side speakers.

The whole point of home audio is for personal enjoyment. If you get down to the nitpicking stage the fun is lost. Yes you can tweak to your hearts content but you don't get to enjoy it.

Also don't forget if something doesn't seem right often turning the amp up can minimize imperfections by having the overall sound level louder.

Another thing to is to try to make sure you have speakers with the wattage rating close to your stereo. It shouldn't have to be an exact match and the speakers don't have to be a matched set. But you don't want to have too much of a disparity on the wattage of the speakers and amp.

[jagabo]

-I see. So it doesnt matter, if my source is mp3,ac3 or dts, it's all going to be downmixed to stereo before it travels to the HiFi system which in turn will deliver the sound to each speaker

Yes.

-My last serious question is this. Is this really better than having a simple 2.0 or 2.1 stereo setup, since this is nowhere near an independent surround setup?

That's your only choice with that system. Try it and see what you think. If you're a musical purist you may not like it. For movies it's usually fine.

It would sound terrible. High frequencies don't bounce off walls very well. The sound would be muted. It's much better to have the speaker above or below but facing the viewer.

Would you rather suggest i dont use the one that is solo, and use a pair of the small ones instead to have it properly up and down the TV set?

As for the ones i mentioned as ground speakers, i cannot get a picture online, but i found this manual. IT seems they are front/center and super woofer all in-one. They even have external connection for rear speakers. Could this may be prefereable?

I did find the manual though.

http://pdf.crse.com/manuals/3856457121.pdf

You need to figure out exactly what each of those speakers is. It sounds like you have more speakers than originally came with the system. Do the big floor standing speakers have grills that you can remove? Or can you see the drivers through the grill? Do you see multiple drivers? If so, those should probably be used for the front left and right speakers. You can choose to use the center in addition, or not.

[yoda313]

If you're a musical purist you may not like it. For movies it's usually fine.

I agree with this. For regular music surround is not ideal. Unless you are talking about a movie concert encoded in surround sound or a dts encoded cd or sacd. But a plain vanilla stereo cd or mp3 track will sound echoey and really off if you push the dolby surround button for a purely stereo source.

But for movies it is a good idea. However if its a really old movie before surround mixes and its not a dvd but a vhs the surround might also through the feel of it off. If you had pro logic 2 on the amp it is supposed to do a fake 5.1 from any stereo source. THe original dolby pro logic isn't as complex. It might sound echoey and not as good as a real dolby surround track.

You can choose to use the center in addition, or not.

I"m not sure how that would alter a dolby surround presentation. If you have four speakers hooked up and hit the dolby surround button will the vocals sound more diffused and get lost without a physical center channel for it to play through?

If you have the center speaker and intend to watch movies in surround sound I would definitely recommend hooking up the center channel.

However if you are only using it for stereo sources like regular music cds than no you don't need the center. You could use a matrixed four channel setup like hall or jazz or something for music to create ambience (albeit fake and will probably detract from the music listening experience)

[jagabo]

You can choose to use the center in addition, or not.

I"m not sure how that would alter a dolby surround presentation. If you have four speakers hooked up and hit the dolby surround button will the vocals sound more diffused and get lost without a physical center channel for it to play through?

If you look at the manual it talks about having a phantom center channel mode for use with the front left/right speakers. And since it also has center channel outputs it must also have a discrete center channel mode.

[yoda313]

If you look at the manual it talks about having a phantom center channel mode for use with the front left/right speakers.

Ok than that sounds like a virtual center channel. So just stereo speakers would be fine with a dolby presentation.

But personally I would go with a physical speaker if you have one anyway. Virtual never seems quite right to me compared to physical layouts.

[smartel]

some amps have main A and main B out ,
i've put my main B output on the sub with ambiant (non-effected) speakers to have a better immersion effect

[CSULB71]

Just wanted to add that the center channel speaker is designed primarily for the vocal dialog in a movie. It is supposed to give you the sense that the actors are speaking directly from the screen.

[jagabo]

Yes, many stereo speakers don't have good imaging so it helps to have a center channel for dialog. Also, you can boost the volume on the center channel to make it stand out more.