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How is LFE made?

krabapple

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The LFE channel -- the .1 channel -- was meant to contain cinema audio for things like explosions, gunshots, volcanic eruptions, and the like . Loud low bass. In practice, for purely musical releases at least, it seems to be (mis)used for whatever the mixer thinks will make the listener notice his subwoofer is working. (Wise heads have argued that an LFE channel should NOT be needed for music releases, as bass management works just fine for people with subwoofers, but the ship sailed long ago)

Anyway, my question is how LFE is actually 'made' in the mixing studio for music releases. Let's also stipulate, for simplicity, that its use will be in a system of full range speakers plus a subwoofer (i.e., no bass management).

Is the content of an LFE 'supposed' to be low passed content created in the studio , which is also *removed* from the other channels (i.e.., they are highpassed)? Or is it supposed to share bass content with the other channels? Or something else?
 

eddantes

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My understanding is that LFE is 120hz hard cut off, with the low pass value being the soft (sloped) cutoff.

As for content - again, I assume - it's just mixed down to mono from all channels available by the receiver/device. I don't know if LFE is embedded in the content directly - but I suppose it can be. I'd be interesting in hearing the authoritative answer to this also.
 

MakeMineVinyl

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There are many ways a LFE channel is made. When I was working in movie sound, sometimes the LFE was created by sound designers when the sound effects were made. Sometimes the LFE was created on the dubbing stage with a DBX box which pitched existing low frequencies in sound effects and music down one octave and this was fed exclusively to the LFE track. Sometimes composers (in especially synth based music) will create an LFE channel themselves which is then mixed into the total LFE channel during final dubbing. There is no standard about how the LFE is created, only technical standards about the LFE track itself.
 

eddantes

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So - it appears one gets a hard low pass at 120hz and up to +10db of additional signal (under 120hz) that a creator has deemed worthy of their creation. If none exists - then it's just the mono mix of available LCR channels as I suspected. Nice!
 

MZKM

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So - it appears one gets a hard low pass at 120hz and up to +10db of additional signal (under 120hz) that a creator has deemed worthy of their creation. If none exists - then it's just the mono mix of available LCR channels as I suspected. Nice!
Fun fact, IMAX does not have an LFE track, it is strictly full range speakers only.
The LFE track thus has to be generated for home releases.
 

Cbdb2

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My understanding is that LFE is 120hz hard cut off, with the low pass value being the soft (sloped) cutoff.

As for content - again, I assume - it's just mixed down to mono from all channels available by the receiver/device. I don't know if LFE is embedded in the content directly - but I suppose it can be. I'd be interesting in hearing the authoritative answer to this also.

Depends how your reciever is set up. Any speakers set to "small" will have there LF set to the sub and this will be added to the LFE (.1) track thats part of the 5.1source. Some recievers have more options for this than others, like different settings for the sub xover freq.
 
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krabapple

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My understanding is that LFE is 120hz hard cut off, with the low pass value being the soft (sloped) cutoff.

If that's the standard, some mixers are breaking it when the format is lossless (rather than Dolby Digital or DTS lossy).

I've encountered multiple examples of full bandwidth content in LFE , e.g,. entire drumkits -- cymbals and all -- or full range bass guitar audible when auditioning the LFE in isolation, over headphones*. And of course, the cymbals etc are also printed to the main channels as well (otherwise it would never be heard in most systems). This is one reason I'm asking how LFE is made.

(Great for learning those parts)
 
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krabapple

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My understanding is that LFE is 120hz hard cut off, with the low pass value being the soft (sloped) cutoff.

As for content - again, I assume - it's just mixed down to mono from all channels available by the receiver/device. I don't know if LFE is embedded in the content directly - but I suppose it can be. I'd be interesting in hearing the authoritative answer to this also.


LFE is content created in the studio, printed to the 1. channel there. I'm interested in that creation step.

I'm not talking about how a consumer's receiver creates a 'subwoofer channel'. That can contain either just the existing LFE content of the .1 channel alone, or LFE + low passed bass from the other channels, or no content at all (LFE is redirected to large mains), depending on bass management.
 
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ace_xp2

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Just crap mixing, there's been all kinds of it in the audio multi channel world over the years. At one point, there was a version of logic 7 which worked on 5.1 audio even if using only 5.1 speakers because so many mixes would just use the front left/right with no center.
 

sarumbear

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the terms LFE and subwoofer are not interchangeable, and the distinction between the two terms is very important. Care should be taken to avoid confusion by using these terms appropriately.

This is why I have a separate subwoofer that only the LFE channel is fed to. I use two subwoofers via a crossover for L & R channels separately. No bass management is used.
 
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