How can you tell if there is any audio content in the subwoofer channel?

[Ian Hoyle]

Hi,

I'm somewhat confused about whether or not my DVD is working
correctly.

I have an (aging) ProLogic amp with 6 channel input (for using an
external decoding source), so I recently purchased a Philips DVD727K
since this had 6 channel out + AC3 & DTS onboard decoding.

My sub is working fine - ProLogic decoded stereo rumbles away just
nicely.

I just watched Terminator 3 in DTS and in those parts of the movie
that used the LFE channel, it too seemed OK.

BUT, I just watched "Legally Blond 2" in Dolby Digital and the
subwoofer didn't cut in once. It seemed like that channel was empty
(for want of a better description). Is there any way of knowing
whether any DVD title has anything recorded on the .1 channel??
(since I was used to the sub being active almost continually on
ProLogic decoded content).

So, I'm in a dilemma. Is my DVD player functioning correctly? Is DTS
working OK, but Dolby Digital decoding stuffed?? Is this a known fault
with this particular player?

Or ..... did I just get unlucky and pick a DVD with no low frequency
content :) (I somehow doubt it)

Ian

[Italo]

"Ian Hoyle" <ianhoyle@yahoo.com> wrote in message
news:a738108.0402181157.41990965@posting.google.co m...

> So, I'm in a dilemma. Is my DVD player functioning correctly? Is DTS
> working OK, but Dolby Digital decoding stuffed?? Is this a known fault
> with this particular player?

You need to adjust the sub & speaker volume/distance settings on your DVD
player (if there are any they should be in the set-up menu of the DVD
player) because the 6 channel input of your amp bypasses all internal
settings except volume control.

To do this 'correctly' you'll need a DVD test disc (your DVD player should
also have built-in test tones) and an analog sound pressure meter. You can
also do it 'by ear' but it won't be very accurate especially for the sub
channel.

--
Italo

[Gary Markham]

I just watched "Legally Blond 2"..
Well theres your problem there.
Do you think a movie like that would have BASS in it to start with?
Was there explosions, gun fights and car chases? i havent seen it but i
doubt it.
Sub worked with T3 so it works, not all movies have BASS.
"Italo" <inottetolati@xmg.ten> wrote in message
news:4033c772$0$28867$afc38c87@news.optusnet.com.a u...
> "Ian Hoyle" <ianhoyle@yahoo.com> wrote in message
> news:a738108.0402181157.41990965@posting.google.co m...
>
> > So, I'm in a dilemma. Is my DVD player functioning correctly? Is DTS
> > working OK, but Dolby Digital decoding stuffed?? Is this a known fault
> > with this particular player?
>
> You need to adjust the sub & speaker volume/distance settings on your DVD
> player (if there are any they should be in the set-up menu of the DVD
> player) because the 6 channel input of your amp bypasses all internal
> settings except volume control.
>
> To do this 'correctly' you'll need a DVD test disc (your DVD player should
> also have built-in test tones) and an analog sound pressure meter. You can
> also do it 'by ear' but it won't be very accurate especially for the sub
> channel.
>
> --
> Italo
>
>

[Ian Hoyle]

"Gary Markham" <gmarkham@internode.on.net> wrote in message news:<4033f652$1@duster.adelaide.on.net>...
> I just watched "Legally Blond 2"..
> Well theres your problem there.
> Do you think a movie like that would have BASS in it to start with?
> Was there explosions, gun fights and car chases? i havent seen it but i
> doubt it.
> Sub worked with T3 so it works, not all movies have BASS.

Agreed and this raises an interesting observation.

Since ProLogic synthesises the sub channel from the original stereo
content, I was very used to having the bass end of the audio I
listened to always being utilised by my subwoofer.

I guess I expected that some of the louder music tracks would use the
sub channel when in 5.1 mode. Looks like the title I selected didn't
do that :)

My 5.1 setup is a smaller Bose system that doesn't have a big bottom
end. Without the sub kicking in (as when I used ProLogic), the audio
sounded noticably flat. That's how I noticed ...............

Ian

[David Williams]

> I guess I expected that some of the louder music tracks would use the
> sub channel when in 5.1 mode. Looks like the title I selected didn't
> do that :)

Maybe you need to look at the crossover you have set in your amp for your
sub - ie if you have the speaker type set to large for your front speakers,
it may not get sent low frequency stuff - if you have the speakers set for
small, the amp will send the low frequencies to the sub (as you have told it
the main speakers can't handle bass) Or perhaps you can have both.

[Italo]

"Ian Hoyle" <ianhoyle@yahoo.com> wrote in message
news:a738108.0402182003.15d95d52@posting.google.co m...

> Since ProLogic synthesises the sub channel from the original stereo
> content, I was very used to having the bass end of the audio I
> listened to always being utilised by my subwoofer.

If you insist on using the analog inputs of this particular amp then you
need to look at the set-up menu in your DVD player. It should have settings
for the analog outputs where you can adjust speaker distance, bass response
and whether the speakers are 'large' or 'small'.

--
Italo

[Byron John Forbes]

"Ian Hoyle" <ianhoyle@yahoo.com> wrote in message
news:a738108.0402181157.41990965@posting.google.co m...

> BUT, I just watched "Legally Blond 2" in Dolby Digital and the
> subwoofer didn't cut in once. It seemed like that channel was empty
> (for want of a better description). Is there any way of knowing
> whether any DVD title has anything recorded on the .1 channel??
> (since I was used to the sub being active almost continually on
> ProLogic decoded content).

The reason it is refered to as .1 is because it is not a seperate
channel. The source (DVD) has nothing to do with it. The .1 channel takes
the low freq sounds from the 5 channels (done either in your amp or player)
and sends it to the subwoofer that is specifically designed to handle these
bass sounds. What is on the channel is dictated by the volume and, more
importantly, the crossover freq selected by the user. The whole idea, of
course, is to take the load of all that bass away from the satelites and
offset distortion in them.

[Ian Hoyle]

"Italo" <inottetolati@xmg.ten> wrote in message news:<403494b6$0$5871$afc38c87@news.optusnet.com.au>...
> "Ian Hoyle" <ianhoyle@yahoo.com> wrote in message
> news:a738108.0402182003.15d95d52@posting.google.co m...
>
> > Since ProLogic synthesises the sub channel from the original stereo
> > content, I was very used to having the bass end of the audio I
> > listened to always being utilised by my subwoofer.
>
> If you insist on using the analog inputs of this particular amp then you
> need to look at the set-up menu in your DVD player. It should have settings
> for the analog outputs where you can adjust speaker distance, bass response
> and whether the speakers are 'large' or 'small'.

No, it isn't that.

I've changed settings from small to large etc etc. I've carefully set
the sizings of the speakers as per the Bose recommendations and have
also checked wiring etc etc a squillion times.

I can only deduce that either:

o some DVDs have zero content in the LFE channel (eg legally blond 2),
or
o my DolbyDigital decoder is stuffed (while DTS is OK).

Ian

[Michael]

Just a little thing, the source as you call it, or encoding method is
referred to as Dolby Surround, Pro Logic is a decoding method, and the rears
are mono in both Pro Logic & the earlier Surround decoding, so that's 4
channels.

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c12i5r$dc7$1@otis.netspace.net.au...
> With the manual one a Dolby Surround or Prologic
> source gives me only five channels (no subwoofer), unless I switch it to
> stereo input.

[Codswallop]

On Wed, 18 Feb 2004 23:45:40 GMT, Gary Markham wrote in aus.dvd:

> Was there explosions, gun fights and car chases? i havent seen it but
> i doubt it.
> Sub worked with T3 so it works, not all movies have BASS.

No but many films like that have -soundtracks-. These soundtracks often
have low-end stuff. Depending on how a system is configured, the bass
kicks etc may be heard on a sub.

--
- Cods
pbqf_at@ubgznvy.pbz (un ROT-13 to email)

Welcome to KILLFILE, population: You.

[Byron John Forbes]

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c12i5r$dc7$1@otis.netspace.net.au...
> Byron John Forbes wrote:
> >
> > The reason it is refered to as .1 is because it is not a seperate
> > channel. The source (DVD) has nothing to do with it. The .1 channel
takes
> > the low freq sounds from the 5 channels (done either in your amp or
player)
> > and sends it to the subwoofer that is specifically designed to handle
these
> > bass sounds. What is on the channel is dictated by the volume and, more
> > importantly, the crossover freq selected by the user. The whole idea, of
> > course, is to take the load of all that bass away from the satelites and
> > offset distortion in them.
> >
> >
>
> No, that is not the case. 5.1 is six discrete channels encoded
> digitally. The .1 indicates it is an "effects" channel or LFE.

So without a subwoofer one is actually missing out on some sound?

>
> In Prologic though, there are four channels matrixed into two, and some
> fairly simple decoding takes place to drive four or five speakers.
> There is no LFE channel though, and in that case it is as you suggested,
> created by using a crossover system to seperate the low frequency audio
> from the higher frequencies.
>
> I have two surround sound systems, and one of them automatically
> switches according to the source, but the other has to be switched
> manually. With the automatic one I get the effect of six channels
> regardless of what I play. In other words if there is no LFE channel it
> will synthasise one. With the manual one a Dolby Surround or Prologic
> source gives me only five channels (no subwoofer), unless I switch it to
> stereo input.
>
> It can be pretty involved, and one of the best descriptions in clear to
> understand language is from How Stuff Works.
>

All my DVD experience is via the computer and a SB Audigy card. In every
situation I have seen so far, if I fiddle with the crossover freq I can add
or subtract bass from the satelites. I have no subwoofer at prersent. It
seems that you're saying that some DVDs already have this done at some
preset crossover and you have no ability to adjust it. I have not seen this
and must say I find it very hard to believe. Any specific examples Oldus? I
always thought this was one of the main features of AC3 ie the ability to
set crossover wherever one likes. Maybe the Audigy always gives this option
whereas all amp/decoders may not?

Come to think of it, maybe this 6 channel stuff is for where there is no
decoder at all apart from in the player itself and the player has no ability
to create an LFE channel? Dunno.

[Byron John Forbes]

Interesting stuff. I must say I'm shocked that some ?5.1? DVDs don't use
the subwoofer at all. I suspect that my Audigy card always makes a .1
channel whether there's one on the DVD or not. Not having a subwoofer
connected yet I can't be sure, but the crossover always seems to be active
so..............................


"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c16b3q$2pi2$1@otis.netspace.net.au...
> Byron John Forbes wrote:
>
> > "Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
> > news:c12i5r$dc7$1@otis.netspace.net.au...
> >
> >>Byron John Forbes wrote:
> >>
> >>> The reason it is refered to as .1 is because it is not a seperate
> >>>channel. The source (DVD) has nothing to do with it. The .1 channel
> >
> > takes
> >
> >>>the low freq sounds from the 5 channels (done either in your amp or
> >
> > player)
> >
> >>>and sends it to the subwoofer that is specifically designed to handle
> >
> > these
> >
> >>>bass sounds. What is on the channel is dictated by the volume and, more
> >>>importantly, the crossover freq selected by the user. The whole idea,
of
> >>>course, is to take the load of all that bass away from the satelites
and
> >>>offset distortion in them.
> >>>
> >>>
> >>
> >>No, that is not the case. 5.1 is six discrete channels encoded
> >>digitally. The .1 indicates it is an "effects" channel or LFE.
> >
> >
> > So without a subwoofer one is actually missing out on some sound?
> >
>
> Depends on your speakers, as some can not handle the lower frequencies.
> >
> >>In Prologic though, there are four channels matrixed into two, and some
> >>fairly simple decoding takes place to drive four or five speakers.
> >>There is no LFE channel though, and in that case it is as you suggested,
> >>created by using a crossover system to seperate the low frequency audio
> >>from the higher frequencies.
> >>
> >>I have two surround sound systems, and one of them automatically
> >>switches according to the source, but the other has to be switched
> >>manually. With the automatic one I get the effect of six channels
> >>regardless of what I play. In other words if there is no LFE channel it
> >>will synthasise one. With the manual one a Dolby Surround or Prologic
> >>source gives me only five channels (no subwoofer), unless I switch it to
> >>stereo input.
> >>
> >>It can be pretty involved, and one of the best descriptions in clear to
> >>understand language is from How Stuff Works.
> >>
> >
> >
> > All my DVD experience is via the computer and a SB Audigy card. In
every
> > situation I have seen so far, if I fiddle with the crossover freq I can
add
> > or subtract bass from the satelites. I have no subwoofer at prersent. It
> > seems that you're saying that some DVDs already have this done at some
> > preset crossover and you have no ability to adjust it.
>
> That is correct. On my surround systems I can not adjust the crossover
> frequency but can adjust the subwoofer volume. There is a limited
> range bass/treble tone control, but that does not affect the frequency
> crossover.
>
> I have not seen this
> > and must say I find it very hard to believe. Any specific examples
Oldus?
>
> Just look at the specifications of any of the surround sound systems,
> and the output methods of the particular dvd player. Our little
> Digitrex 1020 for example, only has two channel analogue outputs and is
> connected to a computer sound system with subwoofer and two speakers.
> It takes the stereo source, uses a crossover to send the lower
> frequencies to the subwoofer.
>
> My other DVD players all have a 5.1 decoders onboard and are plugged
> into six channel systems. Effectively they only amplify the source
> material, so if there is no LFE channel, and are switched to 5.1 mode,
> then the subwoofer remains silent. On other material, and using the
> aux or stereo inputs the system synthesises surround sound, including
> the subwoofer by using a crossover system.
>
> > I always thought this was one of the main features of AC3 ie the ability
to
> > set crossover wherever one likes. Maybe the Audigy always gives this
option
> > whereas all amp/decoders may not?
> >
>
> Basically all you are doing there, without a subwoofer, is using a tone
> control and cutting or boosting the lower frequencies. If your
> speakers can not handle the lower frequencies, then there will be
> distortion, or the sound will be tinny.
>
> > Come to think of it, maybe this 6 channel stuff is for where there
is no
> > decoder at all apart from in the player itself and the player has no
ability
> > to create an LFE channel? Dunno.
> >
> >
>
> Going back thirty or so years of course everything was two channel
> stereo, and generally in the home consisted of two speaker boxes each
> containing two or more speakers. Crossovers in the boxes split the
> audio between various frequencies. We had a brief flirtation with a
> couple of different types of 4 channel sound, but we still ended up with
> quite large speakers to be able to get the bass response we wanted.
> Smaller boxes (generally) tended to be tinny sounding because they
> couldn't reproduce the bass correctly.
>
> The next big thing of course was to go to a subwoofer system which
> seperates the lower frequencies by using a crossover and sends all of
> the lower frequencies to a seperate speaker, suitable beefed up to
> handle the output. This works because generally speaking, the lower
> frequencies are not directional and only one subwoofer is required,
> instead of needing one for each channel. At this stage we are only
> talking of a two channel source. The little system attached to my
> Digitrex is an example of this type.
>
> Rather than bore everyone stupid, I will suggest that if you are
> interested further have a look at How Stuff Works and do a search for
> surround sound http://entertainment.howstuffworks.com/surround-sound.htm
> is a good starting point. You might even find the section on cinema
> sound to be interesting.
>
> --
> Cheers
> Oldus Fartus

[Byron John Forbes]

Went to dolby site and found this as an answer to someone's question -

"With respect to home playback, the terms 5.1, 6.1, and 7.1 mean that
there are five, six, or seven main speakers, plus a subwoofer, in the
playback system. (The subwoofer reproduces the LFE channel recorded on 5.1
soundtracks, plus any bass the main speakers cannot handle.) The difference
is in the number of surround speakers: two in a 5.1 system, three in a 6.1
system, and four in a 7.1 system."

So right you are! :) So it seems they send all the real low stuff to the
sub on the LFE channel and then if you have hardware that allows crossover
adjustment, you can send even higher frequncies to the sub (and, of course,
away from the satelites) in the case where the satelites distort easily.

I still don't like it though! :) I can only assume there's a lot of 5.1
etc amps out there with no crossover feature.

It seems that if I had 4 big speakers with big woofers in them that
there is no way to send the stuff on the .1 channel to them - applicable in
many peoples cases I'll bet. Now I'm wondering if crossover can be used to
send .1 stuff to other channels?! Time for a little more googling :)


"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c17j26$hij$1@otis.netspace.net.au...
> Byron John Forbes wrote:
>
> > Interesting stuff. I must say I'm shocked that some ?5.1? DVDs don't
use
> > the subwoofer at all. I suspect that my Audigy card always makes a .1
> > channel whether there's one on the DVD or not. Not having a subwoofer
> > connected yet I can't be sure, but the crossover always seems to be
active
> > so..............................
> >
>
> I don't have access at the moment to an Audigy card and have never used
> one, but I was under the impression they would output true 5.1 or six
> channels. Someone else will probably no better than I though.
>
> It is true that some supposedly 5.1 DVDs don't seem to make the best use
> of the LFE, but others are simply "wow" when you hear them. Some of
> the scenes in Independence Day, We Were Soldiers, Bat 21 and many other
> movies just blow you away with the rumbling effects. It is sound you
> feel, as well as hear and really add to the viewing experience. The
> first time (for example) you hear a rocket fired somewhere over your
> shoulder, hear it fly overhead and land somewhere in front of you, and
> then feel the room shake from the explosion you are never satisfied
> again with two channel sound.
>
> --
> Cheers
> Oldus Fartus

[Byron John Forbes]

Btw, to the original poster, in my travels I found this
http://www.jvc.com/support/index.jsp?pageID=1&item=16

Down the bottom of the page it mentions that some subwoofers have a
cutoff so........................

[Michael]

"Byron John Forbes" <chocolate@caramel.com.au> wrote in message
news:40388b92@news.comindico.com.au...
> So right you are! :) So it seems they send all the real low stuff to
the
> sub on the LFE channel and then if you have hardware that allows crossover
> adjustment, you can send even higher frequncies to the sub (and, of
course,
> away from the satelites) in the case where the satelites distort easily.

The LFE channel isn't just a subwoofer channel. You can redirect the LFE
channel to your L & R speakers, by telling your decoder you have no sub.

> I still don't like it though! :) I can only assume there's a lot of
5.1
> etc amps out there with no crossover feature.

Every one I've seen does.

> It seems that if I had 4 big speakers with big woofers in them that
> there is no way to send the stuff on the .1 channel to them - applicable
in
> many peoples cases I'll bet. Now I'm wondering if crossover can be used to
> send .1 stuff to other channels?! Time for a little more googling :)

See above.

[Michael]

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c1a60a$239m$1@otis.netspace.net.au...
> As far as I know, no - the crossover frequency can't be changed. It is
> encoded onto the LFE channel (.1), and the amp just processes it and
> sends it to the subwoofer.

No, it sends the .1 to where you tell it to go. It doesn't have to be a
sub.

> I don't believe you could redirect the .1 channel.

Just select 'subwoofer = no' or similar on your receiver/processor/decoder
etc.

> But you could
> certainly switch the player to downmixed stereo which contains all the
> channels mixed into two, and feed them to your speakers and let the
> speaker crossover handle the switching between woofer, midrange and
> tweeter. I have to say though that you still will not get the effect
> of a subwoofer - I have yet to hear normal speakers put out the gut
> rumbling sound of a dedicated subwoofer.

Depends on your budget. Some of the cheap sat/sub combos wouldn't go near
as low as decent floorstanders.

[Michael]

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c1bstp$3d7$1@otis.netspace.net.au...
> Michael wrote:
> > Just select 'subwoofer = no' or similar on your
receiver/processor/decoder
> > etc.
> >
>
> As I said in my other post, all that does is switch off the channel.
> Extra bass does not suddenly appear on the other channels.

I'm afraid you're wrong. It's a fundamental of Dolby decoding that the LFE
can be played by other channels beside the subwoofer. Besides, why would
you bother having a switch to turn the sub off, if it doesn't do anything?

[Michael]

Guess so, or you could read the LFE document on the very first technical
page of the Dolby site.

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c1bs8s$36o$1@otis.netspace.net.au...
> We will have to agree to disagree on that. I still feel the LFE
> channel from true 5.1 source material, can not be redirected to other
> channels.

[Michael]

If you won't take my word for it, why not read the Dolby site's LFE article?
It'd be much quicker than writing big paragraphs reiterating the same error.

"Oldus Fartus" <denisand@netNOSPAMspace.net.au> wrote in message
news:c1cg2q$bal$1@otis.netspace.net.au...
> I will ask again, you are talking true 5.1 audio aren't you? I have
> seen Pro Logic decoders which allow the crossover point to be set to
> whatever frequency you desire and this can have the effect of doing as
> you are suggesting.

Yes, 5.1 and yes good processors/receivers allow you to change the X-over
frequency, but that's not what I'm referring to, and that's not limited to
pro logic btw.

[Byron John Forbes]

Btw, to the original poster, in my travels I found this
http://www.jvc.com/support/index.jsp?pageID=1&item=16

Down the bottom of the page it mentions that some subwoofers have a
cutoff so........................