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Resolved: the "LFE channel" should never be utilized on SACD/DVD-A.


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102 replies to this topic

#1 of 103 OFFLINE   Rich Malloy

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Posted April 23 2003 - 08:44 AM

I'm considering adopting the following Manifesto:

Every studio producing music SACDs and DVD-As should encode full range signals to all 5 primary channels, and never redirect any bass content away from those 5 primary channels to the so-called "LFE" channel.* Bass management should be entirely a function of the playback system, because only the individual user knows the range and limits of his speakers.

*Use of the so-called "LFE" channel for "height envelope" and other experimental playback schemes is permitted so long as the use of this channel is entirely optional.

Or am missing something here?
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#2 of 103 OFFLINE   Brian L

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Posted April 23 2003 - 09:01 AM

Man, I feel your pain, but would this be needed if the various manufacturers got BM right in all formats?

Being a Pioneer 45A owner, I surely appreciate that BM is often handled poorly. Hardly ANY manufacturer gets it right. My player will NOT send the LFE to the mains in DVD-A when I have it set to no sub (don't know about SACD), and it also will not send bass from the mains to a sub when I have my mains set to small.

So, without my trusty ICBM, I am screwed with or without bass on the LFE. I think a lot of others are too. As such, I don't know what this buys us. Until BM is done right, everyone is hosed to one extent of another.

It seems like no one ever had grief with BM when all we had was Pro Logic, but as soon as DD and DTS showed up and we got an LFE channel, stuff started going downhill fast. And then when DVD-A and SACD MC players hit the street, the whole outhouse burned right down.

Brian

#3 of 103 OFFLINE   Justin Lane

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Posted April 23 2003 - 09:12 AM

Since most DVD-A and SACD are labeled where applicable as 5.1 releases, I think it is safe to assume that a subwoofer will be used in a system (or why would one purchase 5.1 music?). It is important to keep the LFE channel, especially for mass market acceptance, for those who have small satellites or HTIB type systems. LFE distributed to smallish speakers, with no form of bass management available could be a big problem. Of course if the engineer doing the album sends boku amounts of bass to the mains, you are going to run into trouble anyway.

The ultimate solution is proper Bass management within the Hi-res players, which doesn't look like it is happening anythime soon. I guess another option would be to mandate engineers to send frequencies lower then a certain level to the LFE regardless, but I don't like the possibilities that may hold either. Really it is a sticky issue which has no perfect solution at this point.

J

#4 of 103 OFFLINE   Kevin C Brown

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Posted April 23 2003 - 09:38 AM

I also think a better solution is for the player makers to get the BM issues *correct*, *and* for the studios/producers to agree that the LFE channel should be bandpass limited to < 200 HZ or so. Then it's a heckuva lot more transparent to people with systems already set up for DVD-V (DD/DTS, etc). (Wasn't that the whole idea behind DVD-A in the 1st place anyway?) Make SACD/DVD-A backwards compatible is all I say... Posted Image
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#5 of 103 OFFLINE   LanceJ

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Posted April 23 2003 - 12:59 PM

I will admit I don't like using the LFE channel for music either.

Question: Ever notice all those Panasonic & Sony hi-res HTiB's with tiny satellites? What are THEY using for bass management???

LJ

#6 of 103 OFFLINE   Wayne Bundrick

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Posted April 23 2003 - 05:26 PM

The manufacturers and the recording labels should stand side by side so that we can deliver a pimp daddy bitch slap to both of them, "Three Stooges" style. Because each of them have surely f***ed things up from opposite directions.

I don't agree with the idea of "DVD-A discs are labeled 5.1 so they assume you really have five speakers plus a subwoofer." I also don't agree that LFE should never be used. That's treating the symptom and not the disease.

I seem to recall that before the DVD-A specification was completed, someone had the presence of mind to include a table of "rosetta stone" data on the disc which would give control on a song-by-song basis over exactly how these six channels of audio are to be downmixed by the player in the event that the listener does not have five speakers plus a subwoofer. I want to know why neither the manufacturers nor the recording labels are using it.

A pimp daddy bitch slap, I tell you. Three Stooges style.
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#7 of 103 OFFLINE   Lewis Besze

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Posted April 23 2003 - 07:06 PM

If a complete BM is adopted in the players universaly,then it won't matter if the LFE channel is utilized.
The new Denon is very promising,that manufacturers start to "see the light".Sound mixers for music,just like the movie counterpart, are endowed with an "artistic licence",they all have different ideas,as how music should be mixed.

#8 of 103 OFFLINE   Brian Perry

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Posted April 24 2003 - 01:10 AM

If memory serves, the reason the .1 (or LFE) channel was added in the first place was because there was the potential that certain bass-heavy movies would oversaturate the capabilities of the 5 primary Dolby Digital channels and that an extra 6dB or so might be necessary. Otherwise, there would really be no need for the .1, as your pre/pro would simply direct bass from the main 5 channels as necessary.

I don't think DVD-A or SACD has this limitation, so I agree with Rich in that the .1 isn't necessary. That's not to say in some systems a subwoofer isn't required--just that the subwoofer can get all the info from the 5 main channels. (Of course, this is complicated by the lack of a digital interface and that BM needs to be handled by the player.)

#9 of 103 OFFLINE   Leo

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Posted April 24 2003 - 06:13 AM

If we were sold a product that stated it was to handle bass management correctly, and in fact doesn't, wouldn't it be considered a defect that should be corrected as a warranty issue?

Just my .02 cents

#10 of 103 OFFLINE   Michael St. Clair

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Posted April 24 2003 - 06:42 AM

It seems that some engineers just dump some of the bass into the .1 channel so that people without bass management still get some bass. I think a few engineers have actually confirmed this. Of course, this means that people with bass management and/or full-range speakers all around may get too much bass.

Quote:
Ever notice all those Panasonic & Sony hi-res HTiB's with tiny satellites? What are THEY using for bass management???


A simple analog combine that duplicates all of the bass in the main channels and adds it to the .1 channel. The speakers are crossed over so high that you aren't going to get any real 'double' bass.

#11 of 103 OFFLINE   Jeff Ulmer

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Posted April 24 2003 - 06:58 AM

LFE should never be used for music. They don't call it Low Frequency Effects channel for nothing. All speakers should be sent full range audio. If a component doesn't have the ability to manage that properly, it is defective.

I am also opposed to mixing in the center channel. For music, 4.0 is the way to go, even if it doesn't fill up all the speakers (which it will, at last to 4.1 if bass managed properly).

The workaround for most of these systems is simply to set your speakers to large, and adjust the crossover point properly.

#12 of 103 OFFLINE   Cees Alons

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Posted April 24 2003 - 07:19 AM

I totally disagree.

Sending the bass to a specific separate channel was done long before we even had 5.1 (or Pro-Logic, or so). Producing bass at several places in a relatively small room is like asking for trouble.

Also, the idea of splitting the frequency range of a channel is a very good idea. There is absolutely nothing wrong with having the bass come from another place, as long as it is produced in that (relatively) small room and the bass frequencies are chosen low enough.

The alternative is multi-driver speakers with cross-overs, which is only a second best solution (cross-over filters have big phase shifts - I wouldn't even call it a solution at all). Bi-amping would be the only proper way to do it, but as said, most of the bass waves of all channels are more or less in phase, and producing them at more than one place is the source of many sound problems.


Note: the original proposition in this thread is a good idea - but I don't think a studio ever sends (records) any non-LFE bass to the LFE-channel. The BM does that.

Cees

#13 of 103 OFFLINE   Rich Malloy

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Posted April 24 2003 - 07:43 AM

Cees, I think perhaps you're missing the point. I agree that reproducing bass at several points in the room is bad. I agree that splitting the frequency range of a channel can (more accurately "may") be a good idea.

But I'm arguing that I should retain control of how I allocate the bass among my speakers. This control should not be assumed by the mixing engineer who does not know my room, does not know my equipment, and does not know my listening preferences. This "one size fits all" approach will clearly be inapt for many systems.

Moreover, there's no small contingent of music-listeners who prefer not to use a sub altogether. Even those whose systems cannot reproduce the full frequency range of the cannon blasts in the 1812 Overture, or the lowest pedals of a pipe organ, may nonetheless prefer the more seamless integration of their main speakers sans sub. You and I may disagree with them, but it should be their choice. And you and I should be free to assign to the sub channel whatever bass you and I choose to, at the frequency point most apt for our systems. I'm simply saying this should not be the choice of the mixing engineer.
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#14 of 103 OFFLINE   Cees Alons

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Posted April 24 2003 - 10:46 AM

Rich,

My first sentence was aimed at Jeff Ulmer's statement.

My two last sentences served to agree with you Posted Image. Except that I don't think any mixing engineer directs bass to another channel than where it should be. However, IF he does, I apparently agreed with your thesis.


Cees

#15 of 103 OFFLINE   LanceJ

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Posted April 24 2003 - 10:55 AM

Thanks Michael. Too bad manufacturers can't include such a simple system in their standalone players. For many people the "small" setting for all their satellites would work fine. Then just a simple b.m. "on/off" button on the front panel would be needed.

Sort of primitve, but better than blowing up your expensive B&W or Dynaudio sats.

LJ

#16 of 103 OFFLINE   Javier_Huerta

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Posted April 24 2003 - 12:33 PM

Hold on a second... if I / anyone else have a 5.1 / 5.0 setup, which is correctly calibrated, I'd assume the following.

1) The 5.1 setup will be able to achieve 20 Hz or lower frequencies, while the 5.0 won't (just because two bass sources usually cancel each other at certain frequencies).

2) Both will practically sound the same over, say, 40 Hz and up.

The only way I see both requisites could not be mutually exclusive would be by using 5.0 channels and letting the user handle the bass management part. As I remember it, I think the Dolby web site used to say the LFE was used to *add* an extra amount of power to bass, and that it shouldn't be mixed to the mains to avoid overpowering them. So, in effect, the LFE would only be appreciated by those with a subwoofer.

Bottom line is - unless it happens to be the "1812 Overture" cannons firing, I don't see any use for an LFE on music... IMHO.

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#17 of 103 OFFLINE   Wayne Bundrick

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Posted April 24 2003 - 01:30 PM

Quote:
If memory serves, the reason the .1 (or LFE) channel was added in the first place was because there was the potential that certain bass-heavy movies would oversaturate the capabilities of the 5 primary Dolby Digital channels and that an extra 6dB or so might be necessary.

Dolby Digital channels are full range and can carry as much bass as any other frequencies.

But the thing about bass is that it takes larger amounts of it to achieve the same perceived loudness as smaller amounts of higher frequencies. The idea of a dedicated channel for bass which is capable of peaking higher than the rest of the frequency range is a good idea.
Wayne Bundrick

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#18 of 103 OFFLINE   Brian Perry

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Posted April 24 2003 - 02:42 PM

Quote:
Dolby Digital channels are full range and can carry as much bass as any other frequencies

I don't think I said anything to the contrary.

Quote:
But the thing about bass is that it takes larger amounts of it to achieve the same perceived loudness as smaller amounts of higher frequencies. The idea of a dedicated channel for bass which is capable of peaking higher than the rest of the frequency range is a good idea.

There are plenty of 2-channel recordings with as much bass as you'd ever want (such as Telarc's 1812 Overture). I guess the question at hand is whether there would ever be a need to add more bass than could be delivered by five full range channels.

#19 of 103 OFFLINE   Philip Hamm

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Posted April 25 2003 - 12:18 AM

I was going to mention the "1812 Overture" cannons as a good candidate for LFE in music as well. Other than that, I agree, the LFE channel should not be used for music, it really isn't needed.
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#20 of 103 OFFLINE   Rich Malloy

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Posted April 25 2003 - 01:52 AM

Quote:
Other than that, I agree, the LFE channel should not be used for music, it really isn't needed.
And more than that, it seems to be creating problems for individual playback systems.

I started this thread because of a question in another thread regarding playback of 5.1 SACDs/DVD-As when one has no sub in the system (as many music-centric systems do not include subs). Since there's no digital interface for bass management, and since every attempt at onboard player bass management severely reduces the resolution of the signal, the only solution that I'm aware of is the "Redirect Switch" on the Outlaw ICBM-1. It would seem that if one did not wish to bear the reduced fidelity of the lame bass management of their player, and one preferred not using a sub, that one must then purchase the ICBM or lose that so-called "LFE" altogether.

And then there's the issue of the 10db difference between movie soundtracks and hi-res 5.1 music. I'm still a tad in the dark on this, but it appears we have two different encoding standards for the "LFE" channel, and this also seems to be causing problems (small? large?) with system calibration.

At any rate, I'd assumed there was a reason why some hi-res music include an "LFE" track, but I hasten to add that many studios never do so, and others seem to depend on the particular album/artist/engineer. What I hope is not occurring is that music is being mixed for "home-theater" systems (or even "home-theater-in-a-box" systems). I understand that one of the biggest technical drawbacks in hi-res music today is the lack of adequate bass management... are these mixes in some way meant to compensate for that? Are we getting compromised mixes as a result of inadequate hardware?
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