Bass in LFE vs Individual Channels

[techsamurai]

Does anyone know what bass goes to the LFE channel vs individual channels?

Someone suggested that anything under 120hz goes to the LFE but that would make the speaker crossover irrelevant as setting it to 40hz or 60hz would be the same as there'd be no frequencies under 120hz. Essentially, the track would set the static crossover and buying floorstanding speakers vs bookshelves would have no benefit in terms of bass in movies.

Also not having a sub would result in terrible sound and we can all agree that movies still sound great without a sub especially if you play full range and have floorstanding speakers at least for the LR.

Which raised the question of what really goes into LFE vs individual channels?

 

[DVDdoug]

The LFE NEVER goes to the regular speakers.

The "LFE" is the "point one" low frequency effects channel on a DVD/Blu-Ray. I don't think it's supposed to go over 80Hz but on the disc it's just one of 6 (or more) channels. It's a separate channel that's not included in the stereo downmix so without a surround decoder and a subwoofer it's lost.

"Bass management" in an AVR is an optional crossover that allows the regular bass from the other channels to be re-routed to the subwoofer. Your AVR may have settings for "large" main speakers, which means the regular bass isn't re-routed to the sub (so the sub wouldn't be used at all with regular stereo music), "medium" which has a lower crossover, or 'small" which has a higher crossover.

If you don't have an AVR your stereo preamp or receiver may have a crossover and a subwoofer output, but it's technically not an LFE. Or the sub may have its own pass-through crossover, or you can have a separate crossover, etc.

 

[Vincentponcet]

It depends on your configuration of the AVR.
The general recommandation is sub(s) get the LFE channel + the low below 80Hz of other channels and other channels got high pass filtered at 80Hz.

 

[techsamurai]

The LFE NEVER goes to the regular speakers.

The "LFE" is the "point one" low frequency effects channel on a DVD/Blu-Ray. I don't think it's supposed to go over 80Hz but on the disc it's just one of 6 (or more) channels. It's a separate channel that's not included in the stereo downmix so without a surround decoder and a subwoofer it's lost.

"Bass management" in an AVR is an optional crossover that allows the regular bass from the other channels to be re-routed to the subwoofer. Your AVR may have settings for "large" main speakers, which means the regular bass isn't re-routed to the sub (so the sub wouldn't be used at all with regular stereo music), "medium" which has a lower crossover, or 'small" which has a higher crossover.

If you don't have an AVR your stereo preamp or receiver may have a crossover and a subwoofer output, but it's technically not an LFE. Or the sub may have its own pass-through crossover, or you can have a separate crossover, etc.

So how does the editor decide how to put the bass in an explosion, say on the right channel?

Obviously, they will need to put bass in the Right channel. Do they put the put the full range of the explosion on the right channel and then add a certain range to the LFE. e.g 20-40hz?

 

[techsamurai]

It depends on your configuration of the AVR.
The general recommandation is sub(s) get the LFE channel + the low below 80Hz of other channels and other channels got high pass filtered at 80Hz.

I know that part. I'm talking about the soundtrack and the frequencies that go into the channels and LFE when the sound editor decides how to master it.

Essentially, the question is "are channels always full range on the soundtrack with bass replicated on the LFE for certain ranges"?

 

[Vincentponcet]

LFE goes up to 250Hz theoretically.
Most recommandes to low pass at 120hz because above there are generally no signal and can be directional from the subwoofer.

 

[Vincentponcet]

I know that part. I'm talking about the soundtrack and the frequencies that go into the channels and LFE when the sound editor decides how to master it.

Essentially, the question is "are channels always full range on the soundtrack with bass replicated on the LFE for certain ranges"?

Sound engineers decides what they want to do.
The channels are 20hz-20khz. The LFE is 20-250Hz. LFE should be able to reproduce 115db SPL peak and chanels should be able to reproduce 105 db sol peak.
The role of the AVR is to move power to loudspeakers according to their capabilities.
If you have a system able to reproduce full scale 20-20k at 105db SPL, then no need to redirect the low to the subs.

 

[Timcognito]

Google says this

 

[techsamurai]

Google says this
View attachment 452873

That's interesting - this suggests that it only has the LF for the LR channels.

 

[techsamurai]

Sound engineers decides what they want to do.
The channels are 20hz-20khz. The LFE is 20-250Hz. LFE should be able to reproduce 115db SPL peak and chanels should be able to reproduce 105 db sol peak.
The role of the AVR is to move power to loudspeakers according to their capabilities.
If you have a system able to reproduce full scale 20-20k at 105db SPL, then no need to redirect the low to the subs.

So all the channels are full frequency which is actually what I experienced when running a system without a sub for 15 years.

The LFE seems to be an extra bass channel on top of the other channels.

 

[Timcognito]

That's interesting - this suggests that it only has the LF for the LR channels.

Depends on the AVR, the content native format, its mix, and your preferred settings as most LF is in the L, R, & sub, but not all. There is usually a chart in the user manual showing what goes where for each setting and format. One great thing to have and set in the AVR is a high pass filter to take a load off the other speakers, typically 80hz stopping high distortion producing LF from entering them. I put the word stereo in my search so that may have changed the AI response as each AVR is slightly different.

 

[techsamurai]

Depends on the AVR, the content native format, its mix, and your preferred settings as most LF is in the L, R, & sub, but not all. There is usually a chart in the user manual showing what goes where for each setting and format. One great thing to have and set in the AVR is a high pass filter to take a load off the other speakers, typically 80hz stopping high distortion producing LF from entering them. I put the word stereo in my search so that may have changed the AI response as each AVR is slightly different.

Still doesn't answer the question of how an explosion's bass on a single channel is split between the channel and the LFE.

Do infrasonic frequencies (<20hz) go to LFE while anything >20hz goes to the channel?

 

[DVDdoug]

So how does the editor decide how to put the bass in an explosion, say on the right channel?

Obviously, they will need to put bass in the Right channel. Do they put the put the full range of the explosion on the right channel and then add a certain range to the LFE. e.g 20-40hz?

So yeah... That's a creative decision but an explosion is clearly an "effect" and for the most impact, it should come from the low frequency effects channel.


An explosion usually contains a wide range of frequencies and if the higher-frequency components come from one side, that's where you'll hear it coming from. Also, the visual will probably dominate your brain.

But it also has to be included in the regular channels (usually at a lower level) for people who don't have a subwoofer (or surround decoder). If it was me, I'd follow the "standard procedure" and put it in both (or all channels). MOST home setups have limited bass so it helps to take advantage of ALL the woofers.

...Apparently, in the original Jurassic Park release they forgot to include the dinosaur footsteps in the main channels. So when people watched it in stereo the video was showing the ground (and camera?) shaking but there was almost no associated sound.

Do infrasonic frequencies (<20hz) go to LFE while anything >20hz goes to the channel?

The (normal) crossover is not that low... There's usually nothing below 20Hz, and often very little below 40Hz. Many home subs (and pro studio subs) go down to 20Hz but most pro subs used live and in dance clubs only go down to around 40Hz. That's the lowest note on a standard bass guitar and it's low enough for bass you can feel in your body. It's a compromise that more-easily allows for high efficiency and high SPL levels in large venues.

 

[techsamurai]

So yeah... That's a creative decision but an explosion is clearly an "effect" and for the most impact, it should come from the low frequency effects channel.


An explosion usually contains a wide range of frequencies and if the higher-frequency components come from one side, that's where you'll hear it coming from. Also, the visual will probably dominate your brain.

But it also has to be included in the regular channels (usually at a lower level) for people who don't have a subwoofer (or surround decoder). If it was me, I'd follow the "standard procedure" and put it in both (or all channels). MOST home setups have limited bass so it helps to take advantage of ALL the woofers.

...Apparently, in the original Jurassic Park release they forgot to include the dinosaur footsteps in the main channels. So when people watched it in stereo the video was showing the ground (and camera?) shaking but there was almost no associated sound.


The (normal) crossover is not that low... There's usually nothing below 20Hz, and often very little below 40Hz. Many home subs (and pro studio subs) go down to 20Hz but most pro subs used live and in dance clubs only go down to around 40Hz. That's the lowest note on a standard bass guitar and it's low enough for bass you can feel in your body. It's a compromise that more-easily allows for high efficiency and high SPL levels in large venues.

I'm of the opinion that bass can be localized down to pretty low frequencies (60hz). An explosion with bass from the speaker is not the same as an explosion with bass from the sub. Maybe for explosions that might work better but for voices or guitars, splitting them is an issue - when I got a sub I had to literally search how low voices and instruments could go because the sub was not a substitute so I saw what you also talked about. Bass is part of the instrument and a voice.

 

[Vincentponcet]

So all the channels are full frequency which is actually what I experienced when running a system without a sub for 15 years.

The LFE seems to be an extra bass channel on top of the other channels.

But not at the same level
LFE peak is at 115db SPL , other channels are at 105db SPL peak.

 

[Vincentponcet]

I'm of the opinion that bass can be localized down to pretty low frequencies (60hz). An explosion with bass from the speaker is not the same as an explosion with bass from the sub. Maybe for explosions that might work better but for voices or guitars, splitting them is an issue - when I got a sub I had to literally search how low voices and instruments could go because the sub was not a substitute so I saw what you also talked about. Bass is part of the instrument and a voice.

Because your main probably cannot provide the same amount of SPL than your mains below 60hz, which is quite normal for 99.99% setups.

 

[techsamurai]

Because your main probably cannot provide the same amount of SPL than your mains below 60hz, which is quite normal for 99.99% setups.

Are you saying that 20hz-60hz can be localized?

 

[masterhw]

I know the LFE channel is by convention optional information that in most implementations is discarded in a stereo downmix. Its certainly true the main channels can contain some pretty low information, and on anything properly mixed they would include everything considered essential. I believe LFE is often additional rumble or non-essential low frequencies that the mixer has reason to believe shouldn't or wouldn't be best served by a main channel.

Someone suggested that anything under 120hz goes to the LFE

You're right that thats wrong. If all speakers are set to full-range, nothing is being diverted to the sub and it is only playing the discrete .1 LFE channel in the mix. When mains are set to crossover, anything below that crossover is being diverted to the sub. This nuance of what the sub is playing can result in tricky language - LFE generally refers to only this dedicated .1 channel in the mix. So what most subs are playing is actually LFE + some amount of mains, depending on the crossover setting.

This is similar but not exactly the same as the LFE+Main subwoofer setting in many AVRs, which lets you choose a universal crossover point (which is separate from each speaker's crossover). This might be what the user you encountered was being confused about, as 120hz is a common default for this setting. I don't believe in most implementations LFE+Main removes anything below 120hz from the main channels, each speaker will still have its own crossover. It just duplicates any frequencies to the sub that might be between the speaker crossover (say 80) and the 120hz LPF.

 

[Oddball]

Decision how to mix low bass content is up to the sound master. Often they will mix the low bass content in individual channels as they deem appropriate.. As noted, whatever is mixed into regular channels will have 105dB limit, provided that mix has that integrity. What goes to LFE will have 115dB limit as LFE gets +10dB boost based on design and AVR processing.

How that really works in a particular system is hard to tell. Depends how you set it up. There are many bass management options out there. But for sure the effects from the regular channel should not be boosted +10dB as for the LFE.

 

[Oddball]

I know the LFE channel is by convention optional information that in most implementations is discarded in a stereo downmix. Its certainly true the main channels can contain some pretty low information, and on anything properly mixed they would include everything considered essential. I believe LFE is often additional rumble or non-essential low frequencies that the mixer has reason to believe shouldn't or wouldn't be best served by a main channel.

You're right that thats wrong. If all speakers are set to full-range, nothing is being diverted to the sub and it is only playing the discrete .1 LFE channel in the mix. When mains are set to crossover, anything below that crossover is being diverted to the sub. This nuance of what the sub is playing can result in tricky language - LFE generally refers to only this dedicated .1 channel in the mix. So what most subs are playing is actually LFE + some amount of mains, depending on the crossover setting.

This is similar but not exactly the same as the LFE+Main subwoofer setting in many AVRs, which lets you choose a universal crossover point (which is separate from each speaker's crossover). This might be what the user you encountered was being confused about, as 120hz is a common default for this setting. I don't believe in most implementations LFE+Main removes anything below 120hz from the main channels, each speaker will still have its own crossover. It just duplicates any frequencies to the sub that might be between the speaker crossover (say 80) and the 120hz LPF.

LFE+main is a setting that most don't really need. If your mains go to below 50hz something to consider. We can talk more if people are interested, but it is quite a bit of niche.