• QuadraphonicQuad welcomes you and encourages your participation! Treat all members with respect. Please keep all discussions civil, even when you have a strong opinion on a particular topic.

    Do not offer for free, offer for sale, offer for trade, or request copies or files of copyrighted material - no matter how rare or unavailable to the public they might be. We do not condone the illegal sharing of music. There are many places on the internet where you can participate in such transactions, but QuadraphonicQuad is not one of them. We are here to encourage and support new multichannel releases from those companies that still provide them and as such the distribution of illegal copies of recordings is counter-productive to that effort. Any posts of this sort will be deleted without notification.

    Please try to avoid discussions that pit one format against another. Hint for new users: make liberal use of the search facilities here at QuadraphonicQuad. Our message base is an incredibly rich resource of detailed information on virtually all topics pertaining to surround-sound. You will be surprised at what you can find with a little digging!

The LFE bug

Help Support QuadraphonicQuad:

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
It appears this has never gotten its own thread here, but it should. It's something that's come up for discussion a lot recently on AVSforum regarding surround audio for high-definition video (HD and Blu-ray). But long before that it had an impact on DVD-A and (possibly) SACD surround mixes. It's the likely cause of the sporadic complains of 'low bass' even from properly calibrated systems.

The problem is that some AVR/player combos do not automatically adjust the level of the LFE channel correctly when it's passed as PCM. In most cases the LFE needs a boost of +10 dB at output -- this is as per Dolby Digital spec for LFE signals, which DTS also tends to follow. This boost also has to happen BEFORE any bass managment takes place, to keep the bass in balance. In effect, this means that when you audition the same 5.1 mix in Dolby Digital and DVD-A formats, the DD may have more bass..and the DD levels are the correct ones.

Virtually all gear performs the LFE boost correctly for bitstream lossy sources -- Dolby Digital/DTS 5.1 passed digitally. Passage as PCM happens in a number of situations, though. When passed as analog, bitstream must be converted to PCM in the player first. DVD-A is always passed as PCM , whether analog or digital. SACD* can be passed digitally via HDMI 1.1 after conversion to PCM. HD and Blu-ray audio is currently always passed as PCM. So the LFE bug potentially affects a variety of sources.


How to compensate? Boosting the subwoofer channel in the AVR would seem one option, but it only works if it is done BEFORE bass management. That's rarely the case for digital sub channel boost. Some AVRs do offer a user an option to boost the analog subwoofer input, to compensate for it when using analog connections -- this catches the LFE before BM. But very few AVRs allow bass management or DSP at all when the analog multichannel panel is used. A few DVD players (like the Oppo970HD) allow an LFE channel boost by the user, which affects both analog and HDMI output; this makes BM & DSP possible downstream for the HDMI connection. I've tried this and it seems to work well for DVD-A (though it suggests the Oppo is already lowering the levels of ALL channels by default, to allow enough digital headroom for the user to apply as much as 10dB of boost to any channel)

Ideally the correct levelling would happen in the AVR, before BM, for all sources passed digitally -- this means being 'smart' about sources that DON'T need the boost (SACD might be one; some old DTS music-only discs are another) , or at least, offering the user the option to turn the boost off (so there could be one preset for SACD/old DTS, and another for all the other formats).

The issue is outlined in detail in this AVSforum thread (first post), along with a growing list of which gear does what:

http://www.avsforum.com/avs-vb/showthread.php?t=748147

Some brands seem already do LFE right (e.g., Denon). Some do it right but disable further DSP. Some mfrs (liek Pioneer) are now offering firmware updates to their AVRs to correct the LFE PCM bug.

*(I'm uncertain whether SACD LFE 'expects' a 10dB LFE boost as a matter of spec, or optionally at the discretion of the mixer, or ever. Some posts by Bob Katz on prosoundweb indicate it doesn't, but he wasn't certain either.)
 
Last edited:

Guy Robinson

2K Club - QQ Super Nova
Since 2002/2003
Joined
Dec 16, 2002
Messages
2,539
Location
Whitby, Ontario, Canada
Great thread. I have found that all formats when using the Oppo have tons of bass if you want that. DVD-A is lower than the other formats however (including SACD) and therefore usually requires more boost on the subs volume control. However, doing that also increases the bass to a pleasing level for DVD-A so everything is good. Still loving my Oppo.:D
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
The only drawback to increasing the bass specifically in the sub cahnnel on the oppo, is that is also boosts the bass for SACD, which may not need it (I still haven't nailed down whether it does or does not). It's not a huge deal, it only means you have to remember to go in and adjust the sub channel by +/- 10dB when switching between DVD-A and SACD.

(The Oppo channel level adjustments don't affect bitstream, so I use the DD levels as the 'defaults' for comparisons/measurements (with my AVR in pure direct mode, no processing except Dolby Digital decoding)) My investigations of the Oppo970 are on that same thread

http://www.avsforum.com/avs-vb/showthread.php?p=9739269&&#post9739269
 

Guy Robinson

2K Club - QQ Super Nova
Since 2002/2003
Joined
Dec 16, 2002
Messages
2,539
Location
Whitby, Ontario, Canada
The only drawback to increasing the bass specifically in the sub cahnnel on the oppo, is that is also boosts the bass for SACD, which may not need it (I still haven't nailed down whether it does or does not). It's not a huge deal, it only means you have to remember to go in and adjust the sub channel by +/- 10dB when switching between DVD-A and SACD.

(The Oppo channel level adjustments don't affect bitstream, so I use the DD levels as the 'defaults' for comparisons/measurements (with my AVR in pure direct mode, no processing except Dolby Digital decoding)) My investigations of the Oppo970 are on that same thread

http://www.avsforum.com/avs-vb/showthread.php?p=9739269&&#post9739269
I just leave it the same for everything and decrease the volume on the rear of the sub if there is too much for some discs.
 

KMO

Member
Joined
Nov 14, 2006
Messages
41
The track recorded on the SACD disc definitely doesn't need a 10dB LFE boost. That's in the SACD spec.

However, multi-format players frequently compensate for this by lowering SACD LFE output by 10dB to put it at standard level and match other formats. So you don't necessarily need to fiddle with the receiver.
 

Frantic

701 Club - QQ All-Star
Joined
Jun 7, 2005
Messages
743
Location
Maryland
Good going guy's!!

This really opens things up for me. Time once again to fiddle around with the settings in an attempt to "Get it right.":smokin

I need to dig into my AVR-3806 manual again. (It's only under my pillow!);)
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
I just leave it the same for everything and decrease the volume on the rear of the sub if there is too much for some discs.

? I don't get this. When are you getting too much to the sub? The LFE bug results in too little sub output.
 
Last edited:

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
The track recorded on the SACD disc definitely doesn't need a 10dB LFE boost. That's in the SACD spec.
Good to know (and good to see you here). You weren't sure of this last time I looked at the thread. Where'd you get the definitive answer about Scarlet book/SACD spec? I've asked the same thing over on prosoundweb but no answer yet.

However, multi-format players frequently compensate for this by lowering SACD LFE output by 10dB to put it at standard level and match other formats. So you don't necessarily need to fiddle with the receiver.
It remains to be determined if the Oppo does this (particularly as it's converting DSD to PCM first, at least when passing it digitally).
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
Good going guy's!!

This really opens things up for me. Time once again to fiddle around with the settings in an attempt to "Get it right.":smokin

I need to dig into my AVR-3806 manual again. (It's only under my pillow!);)

from the AVSforum sticky;

Denon AVR-2307CI, AVR-2807, AVR-3806, AVR-4306, AVR-4806CI(AVC-A11XVA): can set +10dB or 0dB; per-surround mode setting(?) - should allow separate settings for PCM, DSD, DD and DTS
If this is correct, you're all set: just use +10dB for DD, DTS and PCM , and leave DSD at 0 (unless you player also lowers DSD LFE output by 10 dB, in which case, crank that back up in the Denon too!)
 

omega4

Well-known Member
QQ Supporter
Since 2002/2003
Joined
Oct 11, 2003
Messages
175
Location
Luton, UK
I recall a thread some time ago about bass management and in particular using a sub-woofer when decoding SQ, QS, CD-4, all clearly 4.0.

I think I have finally got to "bass heaven" with an Arcam AVR 350 receiver that provides the +10dB for DD, DTS, etc plus a REL Storm sub that has both LFE and high level inputs. The high level is connected via a supplied lead to both front left and right channels, so can act as 2.1 without a low level feed. You can turn off the LFE and use high level only, which REL recommend for music, and turn it on for 5.1 movie soundtracks.

The best feature of all, is that it is remote controlled, so any tweaks, and believe me they are necessary when changing between DTS, DVDA and SACD can be done from the listening position, so no jumping up to change the level. Why aren't all subs remote controlled? It's utterly brilliant!:banana:
 

dbmay75

500 Club - QQ All-Star
Joined
Jun 12, 2008
Messages
577
Location
San Francisco, CA USA
I've got the knob on my sub at 50% and it's set to 0 on my Onkyo. I was listening to a DVD-A today (Celebrating The Music Of Weather Report) and the low end was wayyyyy too much vs. other titles I listen to, but I choose to point fingers at the recording itself, not my equipment. Alas, I grab my remote and lower the sub and go back to enjoying the mix. Like many of you, I own an OPPO 980 and I use the latest firmware to keep any LFE bugs in check. Make sure you have the latest firmware update from oppodigital.com to address any possible LFE issues within your player.
 
Last edited:

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
I recall a thread some time ago about bass management and in particular using a sub-woofer when decoding SQ, QS, CD-4, all clearly 4.0.

I think I have finally got to "bass heaven" with an Arcam AVR 350 receiver that provides the +10dB for DD, DTS, etc plus a REL Storm sub that has both LFE and high level inputs. The high level is connected via a supplied lead to both front left and right channels, so can act as 2.1 without a low level feed. You can turn off the LFE and use high level only, which REL recommend for music, and turn it on for 5.1 movie soundtracks.

The LFE bug never applied to DD or DTS (except when decoded in the player and passed to the AVR as analog); those bitstreams are handled correctly by virtually all AVRs. The LFE bug usually applies to 'PCM' sources such as DVD-Audio or the newer 'hi rez' PCM formats delivered by BluRay players.
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
I've got the knob on my sub at 50% and it's set to 0 on my Onkyo. I was listening to a DVD-A today (Celebrating The Music Of Weather Report) and it was too much vs. other titles I listen to, but I choose to point fingers at the recording itself, not my equipment. Alas, I grab my remote and lower the sub and go back to enjoying the mix. Like many of you, I own an OPPO 980 and I use the latest firmware to keep any LFE bugs in check. Make sure you have the latest firmware update from oppodigital.com to address any possible LFE issues within your player.
AFAIK Oppo firmware does not address the classic "LFE bug", which concerns level of PCM LFE. Failure to create a .1 channel for X.0 material -- which was fixed by firmware upgrade for the 980 -- is NOT the 'LFE Bug' described in this thread.
 

neil wilkes

Moderator
Joined
Feb 6, 2004
Messages
4,301
Location
London, England
AFAIK Oppo firmware does not address the classic "LFE bug", which concerns level of PCM LFE. Failure to create a .1 channel for X.0 material -- which was fixed by firmware upgrade for the 980 -- is NOT the 'LFE Bug' described in this thread.
There should not be any automatic creation of a .1 channel from a .0 mix - unless there is Bass Management set up with "Small" speaker option (as opposed to large) or else where you can choose the point of response on the main channels - anything with a response of less than 20Hz needs to be managed.
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
There should not be any automatic creation of a .1 channel from a .0 mix - unless there is Bass Management set up with "Small" speaker option (as opposed to large) or else where you can choose the point of response on the main channels - anything with a response of less than 20Hz needs to be managed.
Quite so, I was presuming Oppo speakers were set to 'small'. Actually I got the 980s bug(s) wrong; they were:

1) inability to redirect bass from front channels to sub, when source was 96kHz and speakers were set to 'small'

2) passing all X.0 multichannel sources as 2.0 output

Both were fixed by firmware upgrades; neither is the classic 'LFE bug'.
 

leevitalone1

2K Club - QQ Super Nova
Joined
Sep 20, 2006
Messages
3,988
Location
The navel of NY state
I've got the knob on my sub at 50% and it's set to 0 on my Onkyo. I was listening to a DVD-A today (Celebrating The Music Of Weather Report) and the low end was wayyyyy too much vs. other titles I listen to, but I choose to point fingers at the recording itself, not my equipment. Alas, I grab my remote and lower the sub and go back to enjoying the mix. Like many of you, I own an OPPO 980 and I use the latest firmware to keep any LFE bugs in check. Make sure you have the latest firmware update from oppodigital.com to address any possible LFE issues within your player.
I have the same disc and I also must lower bass to 3 or 0, ( analog 5.1 inputs
to my Itegra), so its the disc. just a very instense production freq. wise
 

ssully

2K Club - QQ Super Nova
Since 2002/2003
Joined
Jul 2, 2003
Messages
2,704
Location
in your face
IIRC on that release, bass is doubled: the same bass on the main channels and also on the LFE channel. If so, it was a very silly way of mixing to multichannel. To hear it without the '2X ' bass you'd have to either set speakers to large and turn off the sub, or figure a way to highpass the main channels while sending only the LFE to the sub.
 
2
Top