The wonderful world of LFE

[KMO]

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.

Actually, not having stuff only in LFE is equally standard practice for movie mixes, because downmixes frequently just drop the LFE channel. Dolby rules say that it just gets chucked if you don't have a subwoofer, or if you're outputting to a 2-channel stereo output.

So film mixers absolutely will be putting bass in the mains as well as the LFE, and Dolby guidelines emphasise that's important for the reason above. The vast majority of people playing DVDs or Blu-rays will be using a 2-channel downmix without LFE.

Main variability in music mixes is the LFE level - is it calibrated for playback 10dB louder than main channels like films? Rough consensus seems to be DVD-A and Blu-ray at film +10dB ("0dB" setting in many receivers), and SACD and DTS CD at equal level ("-10dB" in many receivers). You will frequently have to mess with this setting if using SACD, unless something in the chain knows to behave differently automatically (either switching LFE level for PCM versus DSD, or the SACD player itself doing an adjustment when converting to PCM).

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.

If your system is capable of redirecting LFE to mains, doing so shouldn't appreciably alter the level. If it does, that suggests a miscalibration. (Or maybe a receiver bug).

If I had to guess, I'm going to say The Stranger was on SACD, meaning if has an SACD LFE level, so receiver should be set to "LFE -10dB" for it. But you had "LFE 0dB", but had compensated by having the subwoofer 10dB lower than it should be.

Lower LFE 10dB, increase subwoofer 10dB.

(And this sort of nonsense is why mixers shouldn't be using the LFE channel!)

(Don't know about 25 or 6 to 4 - search only found a 4.0 non-LFE mix...)

Another possibility is just that your room is too boomy at the low end, and you've compensated by turning down the subwoofer. With the main speakers playing bass, you don't get that compensation. In which case - plug the speaker ports? Use some EQ?

 

[JediJoker]

Don't know about 25 or 6 to 4 - search only found a 4.0 non-LFE mix...

Presumably, OP was referring to the 5.1 DVD-A mix.

 

[ar surround]

Don't know about 25 or 6 to 4 - search only found a 4.0 non-LFE mix...

Presumably, OP was referring to the 5.1 DVD-A mix.

Yes, I was referring to the DVD-A mix.

 

[MidiMagic]

This is another reason I like matrix. You can't diddle up the mix so it won't play right on some systems.

 

[ssully]

Actually, not having stuff only in LFE is equally standard practice for movie mixes, because downmixes frequently just drop the LFE channel. Dolby rules say that it just gets chucked if you don't have a subwoofer, or if you're outputting to a 2-channel stereo output.

So film mixers absolutely will be putting bass in the mains as well as the LFE, and Dolby guidelines emphasise that's important for the reason above. The vast majority of people playing DVDs or Blu-rays will be using a 2-channel downmix without LFE.

How does that work in practice? What 'part' of the LFE is duplicated in the main channels? Conversely, what is lost when the LFE is dropped?

 

[ssully]

Main variability in music mixes is the LFE level - is it calibrated for playback 10dB louder than main channels like films? Rough consensus seems to be DVD-A and Blu-ray at film +10dB ("0dB" setting in many receivers), and SACD and DTS CD at equal level ("-10dB" in many receivers). You will frequently have to mess with this setting if using SACD, unless something in the chain knows to behave differently automatically (either switching LFE level for PCM versus DSD, or the SACD player itself doing an adjustment when converting to PCM).

A question increasingly pertinent to surround users: What is the consideration when the source is a file ripped from DVDA, BluRay, or SACD?

AFAICT AVRs treat incoming .wav (.e.g bitstreamed from a drive via HDMI) as if it were decoded DD/DTS, e.g. +10dB for the LFE. Therefore for DVDA and BluRay nothing needs to be 'done' to the file.

But I have not verified this with measurement.

All of my 5.1 SACDs are ripped to 88/24 PCM; the AVR doesn't 'know' that they were sourced from DSD; so they are being treated the same as DVDA or BR sourced files. (The SACD ripping software has an option to change the final LFE level +/- 10dB but I leave it as is) This 'should' mean they are getting an unexpected 10dB boost and that 'should' sound unnaturally bassy . Yet to date I have not noticed (sighted listening, no measurement) any consistent difference between SACD sourced music and DVDA/BR sourced in taht dimension. It is an interesting issue.

 

[KMO]

How does that work in practice? What 'part' of the LFE is duplicated in the main channels? Conversely, what is lost when the LFE is dropped?

In a home cinema film mix, an explosion might consist of a 98dB explosion "thud" in the mains, and a 105dB "thud" in the LFE, for about 106dB total on a system with subwoofer using the LFE.

On a system without a subwoofer, where the LFE is dropped, you'll get the much smaller 98dB "thud" just from main channels. (Unless it's a receiver with the option to send LFE to the mains, but you could end up endangering your mains...)

They wouldn't just put a 106dB "thud" in the LFE and nothing in the mains - people without the subwoofer wouldn't hear any "thud".

AFAICT AVRs treat incoming .wav (.e.g bitstreamed from a drive via HDMI) as if it were decoded DD/DTS, e.g. +10dB for the LFE. Therefore for DVDA and BluRay nothing needs to be 'done' to the file.

Well, it's often configurable - there is likely an "LFE level" setting. But it will probably be using the same setting for all such sources. And you've probably got that set to +10dB, so all good for DVDA/Blu-ray rips.

All of my 5.1 SACDs are ripped to 88/24 PCM; the AVR doesn't 'know' that they were sourced from DSD; so they are being treated the same as DVDA or BR sourced files. (The SACD ripping software has an option to change the final LFE level +/- 10dB but I leave it as is) This 'should' mean they are getting an unexpected 10dB boost and that 'should' sound unnaturally bassy . Yet to date I have not noticed (sighted listening, no measurement) any consistent difference between SACD sourced music and DVDA/BR sourced in taht dimension. It is an interesting issue.

I agree it could mean significant boost. The 10dB offset isn't small.

It could be that the LFE option "0" is actually "standard" so is really lowering the data by 10dB to get same output. Sometimes things are labelled funny - like Denon AVRs where "LFE 0dB" means "LFE 10dB higher than mains" and "LFE -10dB" means "LFE same level as mains".

(The fact that it even offers "+10dB" suggests that could be the case. I can't imagine why you'd want to actually add 10dB to the data, so maybe that actually means "don't touch the data, so it ends up 10dB louder").

It could also be that your SACDs have little or no LFE content.

It may also be that your SACDs have always been playing extra bassy - you were getting LFE 10dB hot direct from the disc, and you're still getting that from the rips, so no difference!

I know at least one player doesn't do the lowering during its DSD->PCM conversion - my Sony UBP-X800M2 - so you need to have the receiver set to LFE -10dB if going via PCM.

 

[KMO]

Little thing that's always bugged me - audio editing programs always show all the channels the same height. Even LFE. When authoring for something with +10dB LFE, the LFE channel really should be 3 times the height of the other ones. Then you'd have a more realistic picture of what you were doing. You could actually see that extra headroom

 

[EricKalet]

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

That’s a perfect setting!

 

[Owen Smith]

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.)

I have a 5.0 system with floorstanding L/R. I found the same problem, if I told my amp I didn't have a sub so it mixed the LFE into the mains the bass was completely over powering on most discs. This has stayed constant across DVD and Blu Ray films, and some DVD-A music. I never noticed it on SACDs. I've stopped checking, and I continue to run with the amp thinking I have a sub.

 

[humprof]

Most tech talk is above my pay grade, and I definitely don't have the technical expertise to judge the merits of one self-styled expert's arguments and explanations against another's. But Bob Pariseau's two-part primer on LFE has always seemed sensible to me. (FWIW, Part 2 also seems to speak to the discoveries of LFE phase issues that were all the buzz here a few months ago.)
https://bobpariseau.com/blog/2018/6/5/choosing-a-crossover-frequency-awesome-bass-begins-herehttps://bobpariseau.com/blog/2018/9/3/adjusting-subwoofer-phase-awesome-bass-part-deux

 

[wavelength]

Most tech talk is above my pay grade, and I definitely don't have the technical expertise to judge the merits of one self-styled expert's arguments and explanations against another's. But Bob Pariseau's two-part primer on LFE has always seemed sensible to me. (FWIW, Part 2 also seems to speak to the discoveries of LFE phase issues that were all the buzz here a few months ago.)
https://bobpariseau.com/blog/2018/6/5/choosing-a-crossover-frequency-awesome-bass-begins-herehttps://bobpariseau.com/blog/2018/9/3/adjusting-subwoofer-phase-awesome-bass-part-deux

For years with my setup of 5 identical full range speakers I ran my speakers as "Large" with and without a subwoofer. It was Bob's article "choosing-a-crossover-frequency-awesome-bass-begins-here" that convinced me to try setting all speakers to "Small" and use a subwoofer. IMHO this is the best way to go.

 

[ar surround]

For years with my setup of 5 identical full range speakers I ran my speakers as "Large" with and without a subwoofer. It was Bob's article "choosing-a-crossover-frequency-awesome-bass-begins-here" that convinced me to try setting all speakers to "Small" and use a subwoofer. IMHO this is the best way to go.

I'm curious. What are the size of your full range speakers? And what is the crossover point when speakers are set to "small"?

 

[wavelength]

I'm curious. What are the size of your full range speakers? And what is the crossover point when speakers are set to "small"?

The speakers are Paradigm Studio 60 v2 - 9"w x 15"d x 36"h - 1" tweeter, 7" mid-range/bass unit, 7" woofer.
The crossover is 80Hz.

 

[ar surround]

For years with my setup of 5 identical full range speakers I ran my speakers as "Large" with and without a subwoofer. It was Bob's article "choosing-a-crossover-frequency-awesome-bass-begins-here" that convinced me to try setting all speakers to "Small" and use a subwoofer. IMHO this is the best way to go.

The speakers are Paradigm Studio 60 v2 - 9"w x 15"d x 36"h - 1" tweeter, 7" mid-range/bass unit, 7" woofer.
The crossover is 80Hz.

Yes, I can see how you would have great success setting the speakers to "small" and crossing over at 80Hz for the subwoofer.

 

[Owen Smith]

Yes, I can see how you would have great success setting the speakers to "small" and crossing over at 80Hz for the subwoofer.

Because they are actually relatively small speakers. I have my floorstanding Castle Harlechs handle bass, I have no sub.

 

[timothyemerson]

For years with my setup of 5 identical full range speakers I ran my speakers as "Large" with and without a subwoofer. It was Bob's article "choosing-a-crossover-frequency-awesome-bass-begins-here" that convinced me to try setting all speakers to "Small" and use a subwoofer. IMHO this is the best way to go.

I've also found a big difference when I set my Centre to Small (Audyssey's recommendation too). Way better bass all around.

 

[Wunlow]

Some years back Yamaha used to offer a subwoofer menu setting that had separate LFE and bass management levels that fed to the subwoofer so one could adjust that balance accordingly. This was sorely missed when it was omitted in later models.

 

[ssully]

Correction to my list in the first post

DVDA ELP - Brain Salad Surgery (2000) -- Jerusalem and Toccata and K39 3rd Impression have full range LFE (bass and occasional drum), but Karn Evil 9 1st Impression, and the bonus track Lucky Man, do *not*. The other three tracks are 5.0, they have no LFE.

SACD ELP - Brain Salad Surgery (2008) -- same as above, though the LFE in all cases has a ton of *hiss* that isn't present in the DVDA! This would not be heard from a subwoofer. The mastering is definitely different on this release, though the mix is exactly the same as the DVDA. This actually looks and sounds like it might be a 'pre-mastered' version of the 2000 DVDA -- there is no compression (there is some, not excessive, on the DVDA -- so it sounds louder and punchier when you compare them) and there is hiss that may have been removed from the DVDA, or else it was added during the PCM--DSD conversion.

DVDA ELP - Brain Salad Surgery (2014) (Jakko mix) -- no full range LFE (all tracks have LFE)

 

[neil wilkes]

An LFE is not the same thing as a subwoofer is. I cannot overstate the importance of the distinction between the 2 any more than by linking to the Dolby Professional document that describes the reality.
What the content on an LFE channel ought to be is bandwidth limited. Unless I am told differently - in writing - I will always, always add an 80Hz LPF at a 48dB/Octave slope to all LFE channels at rendering the mix time - the 80Hz is lower than Dolby's recommended 120Hz, but bear in mind Dolby's 120Hz is a brickwall filter - 120Hz will pass, 121Hz will not so we use the 80Hz on steep slope to make the transition smoother and avoid lumpiness.
NON filtered LFE run a very real risk of an MLP Lossless encoding failure - especially if a downmix coefficient is encoded (and unless the 5.1 is going to a PGC-Block group in the Audio_TS then you really do want to include downmix values or else some silly sod will certainly try to play it & then whine relentlessly in another forum I will not mention that his disc is somehow 'flawed' and isn't he oh, so clever to have found this) but that is not why you called (thanks to Alex Belfield for that phrase).
A bass managed subwoofer is an entirely different animal and one we should never even attempt to second guess, as I have seen sub crossover points from as high as 500Hz and suspect there are plenty that go even higher than this. When preparing for DVD-Audio (and Blu-ray & even SACD) we must follow the RPGA 5.1 guidelines so that means doing things the correct way - the .1 is a .1 because it is not full bandwidth. Period, otherwise the mix would not be 5.1 it would be 6.0.
Treating the LFE as full bandwidth is quite simply wrong. To finish off, I will quote a section from the RPGA 'Recommendations For Surround Sound Production (also attached here)
As noted in section 1, the LFE ("Low Frequency Effects") channel was originally introduced by the film industry because early theatrical speaker systems were
unable to generate loud low frequency signals without clipping. Sometimes referred to as the "boom" channel, it is used in film applications to add dramatic
effect, almost exclusively carrying the rumble of volcanic eruptions, spaceships thundering into view, and bombs and planets exploding.
In terms of multichannel music production, however, there is some debate as to whether the LFE channel is necessary at all. One can argue that the home
theater experience is heightened by having the walls shake whenever rocket launchers are fired, but is there really that much value in having the listener feel
every bass drum hit in such a similarly dramatic fashion?
There is no clear-cut answer, but the mere presence of the LFE channel almost dictates that it be used. The danger lies in overuse, because too much reliance
on the LFE channel to carry bass information can result in the loss of low end altogether on incorrectly configured or poorly designed home theater systems. In
addition, the LFE channel is discarded by most matrixed encoding systems (such as Dolby Pro Logic; see section 1.1) and downmixing algorithms (see section
5.5), including those used for HDTV broadcast. Therefore, the LFE channel should never be used to carry the bass content of the main speaker channels —
that is the job of bass management. Because bass management is employed by almost every consumer home theater system, placing too much information in
the LFE channel will effectively result in double management — total bass overload and probable distortion.
Instead, the LFE channel is best approached with caution. Only modest amounts of signal from specific instruments with significant low frequency content — kick drum, tympani, bass guitar, acoustic bass, low organ or piano notes — should be routed to the LFE, and in all instances those instruments should also be printed full range to the desired main channels as well. An experienced mastering engineer can help in correctly assessing the relative level of the LFE channel as compared with the main channels.

Naturally, checks should be made with bass management tools just to give a sanity test and make sure things are in proper phase.
But you certainly don't mix through BM tools.