Why do movies incorporate bass in the main channels?
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Because it is a Low Frequency Effects channel, not a bass channel. The other side of the coin is expressed by those who wonder why the LFE is not in the main channels so they can avoid a sub or simply use a 5.0 or 7.0 system.
Because it is a Low Frequency Effects channel, not a bass channel. The other side of the coin is expressed by those who wonder why the LFE is not in the main channels so they can avoid a sub or simply use a 5.0 or 7.0 system.
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Even when you don't have a subwoofer, you just select "sub none" on your A/V receiver or processor and the LFE channel stuff gets sent to the speakers set as "large." Still doesn't explain why bass is added to the main channels though.
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Not all the time. There are many DVD players (and, I think, some AVRs) that simply discard the LFE in order not to overload the presumably whimpy main channel speakers.
It's not added. It is simply part of the full-range channel.
Not all the time. There are many DVD players (and, I think, some AVRs) that simply discard the LFE in order not to overload the presumably whimpy main channel speakers.
It's not added. It is simply part of the full-range channel.
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Because someone of importance wisely decided that bass management should be done by the end-user, upon reproduction of the soundtrack, and not encoded into the soundtrack at production. Be thankful for that.
After seeing Kal's reply I see that I actually made the same error as you (It's been a rough afternoon
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).The LFE is not a bass channel, the LFE is an effects channel. The bass is already a part of each channels full range signal. You can redirect it by performing bass management.
The LFE is always sent to the sub because it is a separate channel, if you don't have a sub you lose it. As least it works that way with most receivers.
After seeing Kal's reply I see that I actually made the same error as you (It's been a rough afternoon
The LFE is always sent to the sub because it is a separate channel, if you don't have a sub you lose it. As least it works that way with most receivers.
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When I ran my main speakers as "large" and my center and surround speakers as "small" with the subwoofer setting set to "sub none," I could hear bass during the LFE test in AVIA. In AVIA, there is a 5.1 channel identification test where it tests if you can hear every channel. When it came to LFE part of the test, I could hear the bass being outputted through the main speakers that were set as "large."
Quote:
Originally Posted by Easyaspie /forum/post/16870544
After seeing Kal's reply I see that I actually made the same error as you (It's been a rough afternoon).The LFE is not a bass channel, the LFE is an effects channel. The bass is already a part of each channels full range signal. You can redirect it by performing bass management.![]()
The LFE is always sent to the sub because it is a separate channel, if you don't have a sub you lose it. As least it works that way with most receivers.
When I ran my main speakers as "large" and my center and surround speakers as "small" with the subwoofer setting set to "sub none," I could hear bass during the LFE test in AVIA. In AVIA, there is a 5.1 channel identification test where it tests if you can hear every channel. When it came to LFE part of the test, I could hear the bass being outputted through the main speakers that were set as "large."
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Not true at all. I do not know of any AVR that drops the LFE channel when configured as having NO SUB. They all reroute it to the front channels. This is a Dolby requirement of AVRs. DVD players drop the LFE channel from their analog output.
If someone with no sub has a concern about rerouting the LFE channel to their LARGE front speakers, then they should simply set their AVR up as having a sub. Of course, if their AVR behaved like most, and rerouted bass from SMALL channels to the sub, any rerouted bass from any channels that were set to SMALL would not be reproduced with this configuration.
I think that there are some AVRs that may offer some additional settings besides the standard ones found on most AVRs that might allow them to be configured such that a consequence of the settings is that the LFE channel is dropped when the sub out is being utilized.
Right. That is because your AVR was behaving as it should. It reroutes the LFE channel to the LARGE front channels when configured as having NO SUB. Notice, too, that if you set the AVR up as having NO SUB, that the front channels probably automatically default to LARGE and cannot be set to SMALL.
Not true at all. I do not know of any AVR that drops the LFE channel when configured as having NO SUB. They all reroute it to the front channels. This is a Dolby requirement of AVRs. DVD players drop the LFE channel from their analog output.
If someone with no sub has a concern about rerouting the LFE channel to their LARGE front speakers, then they should simply set their AVR up as having a sub. Of course, if their AVR behaved like most, and rerouted bass from SMALL channels to the sub, any rerouted bass from any channels that were set to SMALL would not be reproduced with this configuration.
I think that there are some AVRs that may offer some additional settings besides the standard ones found on most AVRs that might allow them to be configured such that a consequence of the settings is that the LFE channel is dropped when the sub out is being utilized.
Right. That is because your AVR was behaving as it should. It reroutes the LFE channel to the LARGE front channels when configured as having NO SUB. Notice, too, that if you set the AVR up as having NO SUB, that the front channels probably automatically default to LARGE and cannot be set to SMALL.
I believe that the Dolby Digital "no discard" downmix from 5.1 to 2.0 [including LFE] was a requirement for the SD DVD specs [and so imposed on Dolby decoders] - which required a minimum 'full content' DD2.0 downmix [presumably for use with legacy, analog Pro Logic decoders]. That requirement was not imposed on DTS soundtracks on SD DVDs [as the DVD would already include a working DD2.0 or 'downmixable' DD5.1 track] and early DTS decoders sometimes just dropped channels which were not routed to amps/speakers [center, surround, LFE, whatever!] e.g., Technics SH-AC500D [just ask Kal!]
Modern AVRs, quite reasonably, redirect content of missing channels as a receiver [not decoder] function...
I believe that the Dolby Digital "no discard" downmix from 5.1 to 2.0 [including LFE] was a requirement for the SD DVD specs [and so imposed on Dolby decoders] - which required a minimum 'full content' DD2.0 downmix [presumably for use with legacy, analog Pro Logic decoders]. That requirement was not imposed on DTS soundtracks on SD DVDs [as the DVD would already include a working DD2.0 or 'downmixable' DD5.1 track] and early DTS decoders sometimes just dropped channels which were not routed to amps/speakers [center, surround, LFE, whatever!] e.g., Technics SH-AC500D [just ask Kal!]
Modern AVRs, quite reasonably, redirect content of missing channels as a receiver [not decoder] function...
I run my Yamaha HTR-5860 that way to route LFE content through the Left and Right Mains. Note that in this mode the receiver does not generate separate LFE test tones during setup volume balancing [which is by attached speaker, and not by DVD channel!]
I run my Yamaha HTR-5860 that way to route LFE content through the Left and Right Mains. Note that in this mode the receiver does not generate separate LFE test tones during setup volume balancing [which is by attached speaker, and not by DVD channel!]
The LFE channel is a vestige of old cinema sound, from the days before they had proper bass management and enough headroom on the analogue soundtracks for low frequency slam. The so called "full range" speakers in commercial theatres used to go down to around 50Hz or so, meaning the bottom octave was not reproduced well, even with the bass being copied to subwoofers.
70mm six-track releases offered a way to overcome these problems. The six magnetic tracks were supposed to be five screen channels and a mono surround channel. But some mixes used only three screen channels, allowing mixers to use the remaining two as "baby-boom" channels (small frequency range, limited to bass only).
The discrete bass channels helped add extra low frequency impact without overloading the main channels. As theatrical sound went digital, the discrete low frequency channel remained. While soundtracks could probably get by with all the bass in the five main channels, it doesn't hurt to have a dedicate LFE channel. Same reason as before: louder, more impactful bass during playback, without overloading/distorting the main channels during mixing.
It also comes in handy when, like with old movie theatres, proper bass management is not being used (for whatever reason). At least something ends up going to the subwoofer.
70mm six-track releases offered a way to overcome these problems. The six magnetic tracks were supposed to be five screen channels and a mono surround channel. But some mixes used only three screen channels, allowing mixers to use the remaining two as "baby-boom" channels (small frequency range, limited to bass only).
The discrete bass channels helped add extra low frequency impact without overloading the main channels. As theatrical sound went digital, the discrete low frequency channel remained. While soundtracks could probably get by with all the bass in the five main channels, it doesn't hurt to have a dedicate LFE channel. Same reason as before: louder, more impactful bass during playback, without overloading/distorting the main channels during mixing.
It also comes in handy when, like with old movie theatres, proper bass management is not being used (for whatever reason). At least something ends up going to the subwoofer.
If the player downmixed using a Dolby Surround encoder (for use with a Pro Logic decoder later), then the LFE channels was discarded (not to mention the surrounds being summed to mono and bandwidth limited) as part of standard Dolby Surround encoding.
If the player downmixed using a Dolby Surround encoder (for use with a Pro Logic decoder later), then the LFE channels was discarded (not to mention the surrounds being summed to mono and bandwidth limited) as part of standard Dolby Surround encoding.
The Dolby site says "All Dolby Digital decoders, whether 5.1-channel or two-channel, have a unique feature called "downmixing" that assures full compatibility with any playback system. At your choice, the decoder will create "on the fly" from 5.1-channel programs a two-channel mix encoded in Dolby Surround for playback over a home theater system with Dolby Pro Logic decoding [...]" It also indirectly suggests the expected rear channel frequency reduction/restriction from (20 Hz-20,000 Hz) to (100 Hz-7,000 Hz). However, I do not see a specific statement about discarding the LFE channel content during mixdown - nor do I understand why that would be either necessary or desirable. Can you provide any insight...?
The Dolby site says "All Dolby Digital decoders, whether 5.1-channel or two-channel, have a unique feature called "downmixing" that assures full compatibility with any playback system. At your choice, the decoder will create "on the fly" from 5.1-channel programs a two-channel mix encoded in Dolby Surround for playback over a home theater system with Dolby Pro Logic decoding [...]" It also indirectly suggests the expected rear channel frequency reduction/restriction from (20 Hz-20,000 Hz) to (100 Hz-7,000 Hz). However, I do not see a specific statement about discarding the LFE channel content during mixdown - nor do I understand why that would be either necessary or desirable. Can you provide any insight...?
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Not sure what you are pointing out but of course the receiver doesn't generate a subwoofer channel test tone (it's not an "LFE test tone") when configured as having NO SUB. But if you digitally send something from the DVD player to the receiver that is encoded in in the LFE channel only, it will be very obviously reproduced by the front L/ and R speakers.
Not sure what you are pointing out but of course the receiver doesn't generate a subwoofer channel test tone (it's not an "LFE test tone") when configured as having NO SUB. But if you digitally send something from the DVD player to the receiver that is encoded in in the LFE channel only, it will be very obviously reproduced by the front L/ and R speakers.
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The LFE channel is discarded from 5.1 material by DVD players upon mixdown for 2-channel analog output because many DVD players are simply connected directly to a TV via a 2-channel analog connection. A TV's speakers and amplifier are not equipped for LFE reproduction.
The LFE channel is discarded from 5.1 material by DVD players upon mixdown for 2-channel analog output because many DVD players are simply connected directly to a TV via a 2-channel analog connection. A TV's speakers and amplifier are not equipped for LFE reproduction.
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Sorry, poor choice of words on my part...
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I had really intended that to contrast with Kain's reference to a 'Bass test tone' [really an 'LFE channel test tone'] being present when the AVIA test DVD is run, even when no sub is present/attached to the AVR. My bad!
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You are quite right.
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Ah, I see. Wasn't sure what you were saying.
While we are here, I guess it should be pointed out that the subwoofer calibration tones on AVIA are not encoded in the LFE channel at all. They are simply encoded in the main channels and are meant to be bass managed during the calibration. The subwoofer channel identification tone and the LFE channel low frequency sweep on AVIA are specifically encoded in the LFE channel. When an AVR is configured as having NO SUB, these tracks will be rerouted appropriately to the front L/R channels.
Ah, I see. Wasn't sure what you were saying.
While we are here, I guess it should be pointed out that the subwoofer calibration tones on AVIA are not encoded in the LFE channel at all. They are simply encoded in the main channels and are meant to be bass managed during the calibration. The subwoofer channel identification tone and the LFE channel low frequency sweep on AVIA are specifically encoded in the LFE channel. When an AVR is configured as having NO SUB, these tracks will be rerouted appropriately to the front L/R channels.
I understand the position that you and Kal have taken regarding [the positive benefits of] 'LFE discard' during in-player mixdown (viz: in order to provide more general connectivity, e.g., to a tv). However, Kain's post specifically addresses LFE discard during mixdown in AVRs/processors [where the overlapping processes of mixdown and bass redirection can make it difficult to define what is happening where - before we even get to why...]
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I understand the position that you and Kal have taken regarding [the positive benefits of] 'LFE discard' during in-player mixdown (viz: in order to provide more general connectivity, e.g., to a tv). However, Kain's post specifically addresses LFE discard during mixdown in AVRs/processors [where the overlapping processes of mixdown and bass redirection can make it difficult to define what is happening where - before we even get to why...]
Sure. Check out pages 3 & 7 of Dolby's mixing guide for PLII (applies to Dolby Surround encoding as well). Also see the end of page 4 of their DVD guidelines paper.
Sure. Check out pages 3 & 7 of Dolby's mixing guide for PLII (applies to Dolby Surround encoding as well). Also see the end of page 4 of their DVD guidelines paper.
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