The wonderful world of LFE

[ssully]

On a hunch I decided to examine the LFE of most (though not quite all) of my ripped NON lossy 5.1 music collection, spanning DVDA, SACD , and BluRay releases. I didn't check my lossy rips because DD and DTS lossy encoding are *supposed* to enforce a low pass filtered LFE.

By loading a track into Audacity and 'soloing' the LFE channel on headphones, I checked to see whether the bandwidth of the LFE is full range (so if its drums and bass in there, you'll hear the whole kit and all the upper harmonics -- not just a low 'thud') or not. Or something in between

Here's what I found. YES means full range (bass and drums, except as noted), EX means 'in between -- there's extended bass beyond 120Hz, NO means, no, there's only the result of traditional low pass filtering. . I've sorted by artist. You'll note that YESses were found in all three formats. And that there can be inconsistency for a given mixer, or album released >1 time, or and artist, except for Elton John, all of whose 5.1 release have full range LFE.

The upshot: More than a quarter (27/85) of these releases have full range content in the LFE. This has consequences depending on how your subwoofer filtering and bass management are done.

BR    Allman Bros -- Live at the Fillmore     NO
BR    Beatles - Abbey Road      NO
BR    Beatles - Sgt Pepper      NO
DVDA Beatles - LOVE  EX
BR Beatles -- White Album  NO
DVDA    Beck -- Sea Change     NO
DVDA    Beethoven /Kleiber --  5th and 7th       NO
DVDA    Billy Cobham  --Spectrum    YES (drums)
DVDA    Bjork --  Medulla     EX  (vocal spillover)
SACD    Bob Dylan -- Blonde on Blonde       NO
SACD    Bob Dylan -- Blood on the Trcaks      NO
SACD    Bob DYlan -- Love & Theft        YES (drums)
BR    Bob Marley -- Legend  (30th Anniversary)     EX  (bass and kick)
DVDA    Britney Spears  --  In the Zone      NO
SACD    Can  -- Sampler    NO
DVDA    Caravan  -- In the Land of Grey and Pink  (PCM)       YES
DVDA    Chicago II        NO
BR    Chris Squire -- Fish Out of Water    YES
SACD    David Bowie  -- Heathen     EX (vocal spillover)
DVDA    David Bowie --  Stage      NO
SACD    David Bowie  -- Ziggy Stardust       YES (bass)
DVDA    Donald Fagen -- The Nightfly     EX (bass)
DVDA    ELP  -- ELP      YES
DVDA    ELP -- Brain Salad Surgery (2000 )     YES (bass)
SACD    ELP -- Brain Salad Surgery (2008 )     YES (bass, same mix)
DVDA    ELP -- Brain Salad Surgery (2014  JJ)     NO
DVDA    ELP -- Tarkus     NO
DVDA    ELP -- Trilogy     NO
SACD    Elton John  -- Tumbleweed Connection       YES
SACD    Elton John -- Captain Fantastic      YES
BR    Elton John -- Goodbye Yellow Brick Road      YES
SACD    Elton John -- Honky Chateau      YES
DVDA    Flaming Lips -- At War With the Mystucs    EX
DVDA    Flaming Lips -- Soft Bulletin     NO/EX
DVDA    Flaming Lips -- Yoshimi      NO
DVDA    Fleetwood Mac--  Rumours     NO/EX
DVDA    Gentle Giant -- Octopus     YES (bass, except upmixed)
DVDA    Gentle Giant -- Three Piece Suite      YES (except upmixed)
DVDA    Jimi Hendrix -- Electric Ladyland    YES (drums-- kick and hihat )
DVDA    King Crimson --   In The Wake  of Poseidon    NO
DVDA    King Crimson --  Beat     NO
DVDA    King Crimson --  Discipline     NO/EX
DVDA    King Crimson --  In the Court of the Crimson King    NO
DVDA    King Crimson --  Islands     NO/EX (bass)
DVDA    King Crimson --  Larks Tongues      NO
DVDA    King Crimson --  Lizard      NO
DVDA    King Crimson --  Red     NO
DVDA    King Crimson --  Starless & BB      NO/EX (bass)
DVDA    King Crimson --  The ReConstrukcton of Light    EMPTY
DVDA    King Crimson --  THRAK      NO
DVDA    King CRimson --  Three of a Perfet Pair    NO
BR    King Crimson -- In The Court of the Crimson King    YES
BR    King Crimson -- Red     NO
DVDA    KingCrimson --  Spectrum 1984    EMPTY
DVDA    Led Zeppelin -- How the West was Won     EX
DVDA    Metallica  -  Black Album     YES
DVDA    Neil Young -- Harvest      YES
DVDA    Peter Gabriel -- UP     NO
SACD    Pink FLoyd -- Dark Side of the Moon     YES (bass, some drum)
DVDA    Pink Floyd -- Meddle      NO
BR    Pink Floyd -Endless River      EX
DVDA    Rush -- 2112      NO
BR    Rush -- Farewell to Kings 2017 Steven Wilson remix      YES
BR    Rush - Hemispheres     NO
DVDA    Rush -- Moving Pictures     YES
DVDA    Steely Dan -- Everything Must Go     NO
DVDA    Steely Dan -- Gaucho      NO
DVDA    Steely Dan -- Two Against Nature     YES
BR    Steven Wilson -- The Raven That Refues to Sing      YES
DVDA    T Rex -- Electric Warrior     EX
DVDA    Talking Heads  -- Remain in Light     NO
DVDA    Talking Heads --  Speaking in Tongues     NO
BR    Tears for Fears -- Songs from th,e Big Chair      NO
BR    The Who -- Quadrophenia      YES  (and guitar!)
DVDA    The Who -- Tommy      YES
DVDA    Van Morrison -- Moondance      YES
DVDA    XTC  -- Nonsuch     NO
DVDA    XTC -- Oranges & Lemons      NO
BR    Yes - Close to the Edge      NO
BR    Yes -- Fragile (2001 remix)    EX
BR    Yes - Fragile 2015 Steven Wilson remix       YES
DVDA    Yes -- Magnification     NO
BR    Yes -- Relayer      NO
BR    Yes - Tales from Topogra[hic OCeans      NO
BR    Yes - The Yes Album      NO

 

[sukothai]

Another good reason to delete the LFE and let bass management do the job.

 

[Cheezmo]

And don't forget that 90% of releases the LFE is delayed by 4-20ms (there is another thread on that). It's a mess.

 

[paligap]

I'm somewhat ignorant about both the mixing process and bass management. I set crossovers, etc., but I basically let Audyssey do its thing. I don't recall ever hearing any non-LFE type material coming from my subs. As for just deleting the LFE, wouldn't that affect how you hear the mix? I mean, when mixers "send" lower frequency sounds to the LFE, are they also included in the other channels as well?

 

[ssully]

And don't forget that 90% of releases the LFE is delayed by 4-20ms (there is another thread on that). It's a mess.

Still not convinced of the audible effect of that.

Audible effects of LFE bandwidth will be often nil as well, but one can imagine worst case situations where it might have a significant effect.

I'm somewhat ignorant about both the mixing process and bass management. I set crossovers, etc., but I basically let Audyssey do its thing. I don't recall ever hearing any non-LFE type material coming from my subs. As for just deleting the LFE, wouldn't that affect how you hear the mix? I mean, when mixers "send" lower frequency sounds to the LFE, are they also included in the other channels as well?

TYpically there is a lowpass filter applied *by the AVR* specifically to its LFE channel (the adjustable control is called 'LPF for LFE' in some AVRS) . And even if taht weren't the case, the subwoofer itself typically has a user-adjustable filter dial on it . one or both of these will prevent the sub having to deal with high frequency input.

However if your goal is that everything above 80Hz from the sub is rolled off rapidly ...and the LFE has content up to 20kHz....and your AVR LPF is set at 250 ...and your sub crossover dial is set high too ,,..then you are not going to achieve your goal And the sub will be localizable.

As for 'deleting the LFE' he means, the mixer should simply not even utilize an LFE channel in the first place. Put all the bass in the main channels. Let bass management send the low bass to subs . Problem solved.

 

[KMO]

Use of the LFE channel in multichannel music is basically a fudge to deal with the situation in the early 2000s where neither SACD nor DVD-A players would output multichannel over anything other than RCA interconnects, and pretty much no-one could do bass management on those signals. AV receivers normally only have 2-channel ADCs. So the multichannel input bypasses digital processing, including bass management.

So producers put some of the bass into the LFE channel so at least some of the bass reached the subwoofer on a 5.1 sat+sub setup.

There's really not much point in this any more - the vast majority of listeners will now have receivers and players that can pass LPCM or DSD or lossless bitstreams digitally over HDMI and get full bass management (and room EQ and all other trimmings). This is standard functionality in the most basic disc player and AV receiver. Those not using AV receivers will almost certainly have full-range speakers - at least left/right.

The presence of an LFE channel gives so much scope for screwing up the mix - either at source end or playback end - by phase, delay, level and more, that the potential downside of using it is higher than the potential downside of not using it.

Best to leave the LFE out, and concentrate bass on the front-left/front-right. Quite a few people are now omitting the LFE or leaving it empty - eg all Vocalion quad rereleases have empty LFE channels. (Not sure whey they don't leave it out altogether to save disc space - SACD supports 2.0, 5.0 and 5.1).

In fact I'm not really sure why so many people are still using LFE - particularly on modern formats like Blu-ray, where people will be bitstreaming the data off...

 

[Simplepast Presentperfect]

On a hunch I decided to examine the LFE of most (though not quite all) of my ripped NON lossy 5.1 music collection, spanning DVDA, SACD , and BluRay releases. I didn't check my lossy rips because DD and DTS lossy encoding are *supposed* to enforce a low pass filtered LFE.

By loading a track into Audacity and 'soloing' the LFE channel on headphones, I checked to see whether the bandwidth of the LFE is full range (so if its drums and bass in there, you'll hear the whole kit and all the upper harmonics -- not just a low 'thud') or not. Or something in between

Here's what I found. YES means full range (bass and drums, except as noted), EX means 'in between -- there's extended bass beyond 120Hz, NO means, no, there's only the result of traditional low pass filtering. . I've sorted by artist. You'll note that YESses were found in all three formats. And that there can be inconsistency for a given mixer, or album released >1 time, or and artist, except for Elton John, all of whose 5.1 release have full range LFE.

The upshot: More than a quarter (27/85) of these releases have full range content in the LFE. This has consequences depending on how your subwoofer filtering and bass management are done.

Thank you for the list ! I have my own, unfortunately not as detailed as yours, let me copy below the releases where I found a full range LFE (so the YES in your list). I removed items that you already listed.
I also have observed in some releases a LFE channel that extends up to about 300 Hz, but haven't looked into that in detail.

Pixies Doolitle
Carpenters Singles 1969-1981
Tears for Fears The Seeds of Love
Gentle Giant Gentle Giant
Gentle Giant The Power and the Glory
Marillion Misplaced Childhood
Marillion Clutching at Claws
Marillion Brave
Marillion Afraid of Sunlight
Nektar Journey to the Centre of the Eye
Rush Fly by Night
Rush Moving Pictures
Rush Signals
Deep Purple Concerto for Group and Orchestra
Elton John Elton John
Elton John Madman across the Water
Grateful Dead American Beauty
Grateful Dead Workingman's Dead
Meat Loaf Bat out of Hell
Primus Saling the Seas of Cheese
The Jimi Hendrix Experience Electric Ladyland

By the way, around the time I got started with surround I found a CD-DTS of the Carpenters' Singles 1969-1981 when travelling in China.
Amazingly, those DTS files have ALSO full range LFE.
I didn't think that this was possible ?

 

[ar surround]

Thank you for the list ! I have my own, unfortunately not as detailed as yours, let me copy below the releases where I found a full range LFE (so the YES in your list). I removed items that you already listed.
I also have observed in some releases a LFE channel that extends up to about 300 Hz, but haven't looked into that in detail...

Grateful Dead Workman's Dead...

Interesting thread. I just got Workingman's Dead recently, ripped it to the hard drive, and soloed the LFE in Audacity. I was a bit shocked to hear all the "content" in the LFE compared to other stuff I've looked at.

I also noticed that my Lex processor has variable crossover frequencies for the SUBWOOFER channel. I've always wondered why it has this feature as I thought that crossover points only applied to the other 7 speakers for frequencies to be directed to the subwoofer. So it might be interesting to play around with this crossover frequency a bit given that I currently direct all LFE signals to the fronts and surrounds.

 

[ssully]

By the way, around the time I got started with surround I found a CD-DTS of the Carpenters' Singles 1969-1981 when travelling in China.
Amazingly, those DTS files have ALSO full range LFE.
I didn't think that this was possible ?

From my reading it seems there was at least one anomalous DTS *movie* release that had full range LFE , back in the day. So it happens. The low pass filtering for DTS LFE is switchable , from what I understand. Someone involved in encoding neglected to use it.

The other explanation could be that your Chinese disc is a bootleg. ;>

 

[sukothai]

In my experience with 5.1 music discs, the LFE is redundant. So, if you have bass management, the easiest way to eliminate any LFE problems is to convert to flac files and remove the LFE channel. All of the bass content is in the fronts and will be directed to your sub per your crossover settings.

Note: I don't know if this is true for object oriented systems like Atmos.

 

[paligap]

As for 'deleting the LFE' he means, the mixer should simply not even utilize an LFE channel in the first place. Put all the bass in the main channels. Let bass management send the low bass to subs . Problem solved.

I thought he was referring to us deleting it as consumers. It appears that his comments in post #10 confirm that. (I would have done a multi-quote, but I haven't learned how to do that on this forum.)

 

[paligap]

In my experience with 5.1 music discs, the LFE is redundant. So, if you have bass management, the easiest way to eliminate any LFE problems is to convert to flac files and remove the LFE channel. All of the bass content is in the fronts and will be directed to your sub per your crossover settings.

Note: I don't know if this is true for object oriented systems like Atmos.

Is all the bass content in the fronts? In other words, do the fronts contain the same bass content that the mixer sent to the LFE channel? If not, wouldn't deleting the LFE result in deleting some content?

 

[sukothai]

I thought he was referring to us deleting it as consumers. It appears that his comments in post #10 confirm that. (I would have done a multi-quote, but I haven't learned how to do that on this forum.)

I agree with ssully that it would be ideal of the mixers deleted the LFE (and some do) but we have the power as consumers as well.

Is all the bass content in the fronts? In other words, do the fronts contain the same bass content that the mixer sent to the LFE channel? If not, wouldn't deleting the LFE result in deleting some content?

Yes, by redundant, I meant that all bass is contained in the fronts and some or all of the bass will be in the LFE as well. This was necessary because older systems often didn't have a subwoofer.

 

[ssully]

I thought he was referring to us deleting it as consumers. It appears that his comments in post #10 confirm that. (I would have done a multi-quote, but I haven't learned how to do that on this forum.)

I don't know that he or anyone can definitively say that LFE is always redundant on every X.1 music release since ~1999. It would be nice to know. If the LFE consists of actually low passed frequency content, and the rest of the channels are complementarily high-passed, in the mix itself, then you definitely would NOT want to delete the LFE content after the fact.

 

[KMO]

Yes, by redundant, I meant that all bass is contained in the fronts and some or all of the bass will be in the LFE as well. This was necessary because older systems often didn't have a subwoofer.

Well, obviously if the LFE has anything in it, just dropping it will change the result. Assuming it's (roughly) in phase and is just a low-pass filtered copy of the mains, then you won't lose any discrete content, but the bass level will be reduced.

This loss of bass could be roughly compensated for by nudging the subwoofer level up a bit.

Or, if you're doing this edit yourself, if you've got the headroom, add the LFE to both FL and FR, rather than dropping it. (Remembering to scale up 10dB if not SACD for the basic LFE level difference, and down by 3dB (I think) to compensate for it going into two channels).

If [...] the rest of the channels are complementarily high-passed, in the mix itself, then you definitely would NOT want to delete the LFE content after the fact.

That should never be the case. Just as the LFE is being included for compatibility with sub+sat+no bass management systems, the mains will also include bass for compatibility with full-range mains+no-sub systems.

The balance of bass between LFE and mains may vary, but there will always be some in both if the LFE is in use.

 

[Mr. Afternoon]

Yes, by redundant, I meant that all bass is contained in the fronts and some or all of the bass will be in the LFE as well. This was necessary because older systems often didn't have a subwoofer.

I actually have 1 or 2 tracks that has content only in the subwoofer channel on one of my previous releases. Oops!

 

[ssully]

Well, obviously if the LFE has anything in it, just dropping it will change the result. Assuming it's (roughly) in phase and is just a low-pass filtered copy of the mains, then you won't lose any discrete content, but the bass level will be reduced.

This loss of bass could be roughly compensated for by nudging the subwoofer level up a bit.

Or, if you're doing this edit yourself, if you've got the headroom, add the LFE to both FL and FR, rather than dropping it. (Remembering to scale up 10dB if not SACD for the basic LFE level difference, and down by 3dB (I think) to compensate for it going into two channels).

Well then once again we are getting into questions what sound the producer *intended* the listener to hear at home.

That should never be the case. Just as the LFE is being included for compatibility with sub+sat+no bass management systems, the mains will also include bass for compatibility with full-range mains+no-sub systems.

The balance of bass between LFE and mains may vary, but there will always be some in both if the LFE is in use.

You're sure this is standard practice among music 5.1 mixers? Because I would not expect it to be so among *movie* 5.1 mixers, where the LFE is specifically meant for providing loud bassy sound effects. But there, LFE parameters are standardized. I know of no such standards among music 5.1 mixers and indeed have been told that is the reason I see such variation in LFE use in music mixes.

 

[AYanguas]

I understand that the potential downside of using LFE and screwing up the mix (phase, delay, level) is low enough to be almost undetectable for some of us.

But, in case we want to mess around to improve our listening, without ripping, playing with Audacity with changing the LFE delay or removing completely the LFE, I'm thinking now about other alternative:

Remove the Subwoofer speaker in the AVR settings (asuming you have enough full bandwith main speakers). Then all LFE content would be redirected, or added up to the main speakers. No Bass Management all speakers 'LARGE'.

Does this have any sense? Or in a problematic mix, we would still have the same problems?

 

[ar surround]

I understand that the potential downside of using LFE and screwing up the mix (phase, delay, level) is low enough to be almost undetectable for some of us.

But, in case we want to mess around to improve our listening, without ripping, playing with Audacity with changing the LFE delay or removing completely the LFE, I'm thinking now about other alternative:

Remove the Subwoofer speaker in the AVR settings (asuming you have enough full bandwith main speakers). Then all LFE content would be redirected, or added up to the main speakers. No Bass Management all speakers 'LARGE'.

Does this have any sense? Or in a problematic mix, we would still have the same problems?

I don't know about doing this. When I first set up my system, I had the SUBWOOFER set to "none" and determined that the bass at times was way too strong with the LFE routed to the mains/fronts. (Especially material with the kick drum in the LFE.) Two problematic songs I can think of were The Stranger and 25 or 6 to 4. I've also found that setting the CENTER speaker to "none" changes the nature of the mix on some albums.

 

[paligap]

So if I have my LPF for LFE setting at 120Hz, this wouldn't really be a problem for me, right?