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Using Dolby Pro Logic to Play 5.1 DTS DVDs

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Anonymous
January 22, 2005 2:39:43 AM

Archived from groups: rec.audio.tech (More info?)

I have an old home theater system with Dolby Pro Logic. I noticed that most
of the DVDs now just have 5.1 as an audio option. Will the Dolby Pro Logic
still work with 5.1?
Anonymous
January 22, 2005 2:39:44 AM

Archived from groups: rec.audio.tech (More info?)

In article <3pgId.11103$8u5.3176@bgtnsc04-news.ops.worldnet.att.net>,
"Mark Williams" <MarkWilliam@att.net> wrote:

> I have an old home theater system with Dolby Pro Logic. I noticed that most
> of the DVDs now just have 5.1 as an audio option. Will the Dolby Pro Logic
> still work with 5.1?

Pro Logic is one of Dolby's hacks to encode and decode surround sound
using two analog channels of storage. It uses signal phase hints to
shift the sound amplitude between speakers. It has marginal, even
annoying, performance. Human ears already use stereo phase to interpret
placement.

5.1 surround is five independent channels plus a <120Hz channel. You
can get 5.1 surround either using a DVD player and amplifier with analog
5.1 connections or a DVD player with digital audio output and an
amplifier with a Dolby Digital decoder.

Dolby Pro Logic can be applied to stereo signals too. It doesn't quite
work right, but then it doesn't do a whole lot with a real Pro Logic
source anyway.
Anonymous
January 22, 2005 11:42:43 PM

Archived from groups: rec.audio.tech (More info?)

Mark Williams <MarkWilliam@att.net> wrote:

> I have an old home theater system with Dolby Pro Logic. I
noticed that most > of the DVDs now just have 5.1 as an audio
option. Will the Dolby Pro Logic > still work with 5.1?

Dolby Pro Logic was originally the home theater playback
implementation for Dolby Surround used for movies. Dolby Pro
Logic (as opposed to Dolby Pro Logic II) required sources that
were specifically 'matrixed' as two-channel Dolby Surround --
that is, they had extra channel information intentionally
'matrixed' into a two-channel source, at the production stage --
in order to work correctly. It could also 'do stuff' to normal
two channel sources, but that was hit or miss. For matrixed
sources it generated the intended 'four channel' output: three
different front channels and a monophonic 'surround' channel.
The back channel was also bandwidth-limited (did not reproduce
the full audio frequency range)

The newer Dolby Pro Logic II, while also operating on the
'matrixing' principle, is intended for use with *any* two-channel
source, to generate a reasonable semblance of 5-channel
'surround' (plus bass management for a subwoofer). It can output
stereo surround channels as well as three front channels, all at
full bandwidth. It can also correctly decode older Pro Logic
(Dolby Surround) encoded material. (I imagine there are also
sources that have been mixed specifically with DPL II playback in
mind, though I haven't seen that on CDs...maybe video games?)

The even newer Pro Logic IIx does the same trick, but generates 7.1 surround
from 5.1 material.

The 5.1 option on most DVD discs, however, is 'discrete'
surround: Dolby Digital or DTS. This isn't synthesizing more
channels from less, as Pro Logic does; the soundtracks are
already recorded as six separate (discrete) channels.

Dolby Pro Logic won't decode DD or DTS 5.1 sources, nor will DPL
II. It's a whole different technology. (A *two channel* Dolby
Digital or DTS soundtrack could be rendered into 'surround' by
DPL II, though -- but the chances of it sounding like a discrete
5.1 channel DD/DTS mix of the same, are slim).



--

-S
If you're a nut and knock on enough doors, eventually someone will open one,
look at you and say, Messiah, we have waited for your arrival.
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Anonymous
January 23, 2005 2:25:50 AM

Archived from groups: rec.audio.tech (More info?)

Thank you Kevin and Steven for the information!

It sounds like it is time for me to buy a new system. Any recommendations
on what I should go and listen to that is a reasonable price, but still a
good system.
Anonymous
January 23, 2005 2:30:43 AM

Archived from groups: rec.audio.tech (More info?)

What great information.... thank you Kevin and Steven!!!

It sounds like it is time for me to buy a new system. Any recommendation on
a good system that I should go listen to that is a reasonable price.
Anonymous
January 23, 2005 2:30:44 AM

Archived from groups: rec.audio.tech (More info?)

In article <DmBId.14535$8u5.1504@bgtnsc04-news.ops.worldnet.att.net>,
"Mark Williams" <MarkWilliams@att.net> wrote:

> What great information.... thank you Kevin and Steven!!!
>
> It sounds like it is time for me to buy a new system. Any recommendation on
> a good system that I should go listen to that is a reasonable price.

I recently tried a Kenwood receiver and was so disappointed by it that I
returned it the next day. The most basic features of an amplifier were
missing, apparently displaced by numerous silly and useless DSP sound
effects. Kenwood is still grossly overstating their power output too.

I went with an Onkyo 602 and am very happy with it. My favorite feature
is that it has an EQ for each speaker so you can match up their tonal
characteristics. It makes the movement of sound between speakers
seamless. I'm using it in 5.1 + Zone 2 mode, with Zone 2 driving an
infrasonic woofer off the main subwoofer output. It has all of the
modern digital decoders that let you get perfect sound from any cheap
DVD player with digital output. Time will tell how well the Onkyo is
built. The inside is full of patch cables that may eventually become
unreliable from corrosion on the contacts.

Yamaha and Denon make some excellent products but I wasn't able to try
out the models I was interested in. Denon sometimes gets a bit silly
with audiophile voodoo but their base line looks sensible. The
construction of both brands is solid.
!