LFE and SACD

[JojoBar]

Hello,
I'm aware that the LFE is for .1 chanel and is -10dB.
My JBL SW has a switch : "LFE" or "Normal". I guess this manages the -10dB or 0dB. It's configured with LFE.
My amp (Yammie Z11) is configured to output both LFE and bass frequencies to SW.
Bass on SW is correct with films and music, even stereo when using various DSP settings. No SW when the amp is in "Pure" audio mode (no DSP).

My question is when I listen SACD music (DSD 5.1) in PURE mode, do I need to switch the SW to "Normal" or does the amp manage the -10dB level ?

 

[recruit]

My guess is when you are engaging PURE mode you are bypassing all bass management in the amp and only a full range signal is being sent to either or L/R or all your speakers, its like having a DIRECT mode if you like in other amps...I maybe wrong but are you lacking bass or can you check if you are getting any bass out of the sub at all?

 

[JojoBar]

Thank you, I know that in PURE mode, no DSP processing, therefore no redirection of bass to SW. Stereo in PURE mode : the SW sleeps (no signal).
But with DSD SACD, there is 5.1 chanels so .1 direct to the SW, even in PURE mode : the SW is alive, I can ear it ...
But lacking of a SACD reference test disc, the SW being switched "LFE", I don't know if the bass volume is correct (the amp does the correction as it does for DD or DTS) or is -10dB.
That is my question.

 

[Mark.Yudkin]

Thank you, I know that in PURE mode, no DSP processing, therefore no redirection of bass to SW. Stereo in PURE mode : the SW sleeps (no signal).
But with DSD SACD, there is 5.1 chanels so .1 direct to the SW, even in PURE mode : the SW is alive, I can ear it ...
But lacking of a SACD reference test disc, the SW being switched "LFE", I don't know if the bass volume is correct (the amp does the correction as it does for DD or DTS) or is -10dB.
That is my question.

The subwoofer, the amplifier, and whether you're using pure mode or not are all irrelevant, it's entirely a function of the player's behaviour. Bear with me please while I try to explain.

Reference level on DVD is defined as: a full peak swing is 105dB, but 115dB on the LFE channel. To achieve the 115dB level, it is necessary to compress the LFE channel prior to mastering the DVD, and the 10dB LFE setting is used to expand the compressed signal. This is the LFE -10B you're aware of.

Since music doesn't have low frequency effects, the SACD standard has no architected LFE channel, the -.1 is in essence a bass redirection, not a low frequency effects, channel, although architurally it's actually a full range channel. Multichannel SACDs either come in 5.0 or 5.1, where the 5.1 is essentially just the manufacturer applying bass redirection during mastering, and is mostly used in US sourced SACDs (e.g. Albany), with Europeans typically using 5.0, and as a result most classical SACDs are 5.0. The SACD standard clearly states that the .1 channel (if present) does not need a +10dB boost, but as so often, things are not that simple in practice...

Most SACD players support bass redirection as part of the multichannel SACD replay thus supporting your subwoofer with 5.0 sources. However this is where things get messy. Many players, and most recent players, subsequently drop the level of the .1 channel prior to the analogue output so that the user can leave his A/V player consistently set at +10dB. Other players, especially earlier players, leave the .1 channel alone, meaning the user has to fiddle around with the +10dB setting when using the analogue inputs for both SACD and DVD-V. A few players have a setting to let you make up your own mind.

Summarizing therefore: what you have to do in your case is dependent on how your unidentified SACD player behaves. You will need to consult the player's manual to determine what it does or whether the behaviour can be configured.

 

[JojoBar]

OK, thanks : it's clear but not so simple ... I'll have a look,on the Oppo setup and manual !
At the moment I can leave the set as is because switching the SW to "normal" lower the bass (10dB, I guess).
My SACD are 5.1 and in Pure audio (no processing), I can ear the bass ...

Thanks again.

 

[Mark.Yudkin]

OK, thanks : it's clear but not so simple ... I'll have a look,on the Oppo setup and manual !
At the moment I can leave the set as is because switching the SW to "normal" lower the bass (10dB, I guess).
My SACD are 5.1 and in Pure audio (no processing), I can ear the bass ...

AFAIK, all Oppo BD players attenuate the subwoofer level on SACD replay so as to permit a single setting further down the chain. On other words, you will need to apply a 10dB boost for SACD.

 

[Mr Incredible]

How does this relate to the LFE on a 5.1 DTS Audio disc? There's a note in my Denpn amp which says the LFE must be reduced by 10dB if playing DTS music, but not films. Is it expected that the LFE is boosted and cut manually whenever different music source material is played (i.e. SACD vs DTS?).

 

[Member 639844]

How does this relate to the LFE on a 5.1 DTS Audio disc? There's a note in my Denpn amp which says the LFE must be reduced by 10dB if playing DTS music, but not films. Is it expected that the LFE is boosted and cut manually whenever different music source material is played (i.e. SACD vs DTS?).

I have a ten year old DVD player that gives the option to chop 10db from the LFE channel. I never really understood why ten years ago but I guess it makes sense for music playback.

This really begs the question as to how the discrete .1 channel is dealt with for music content. Is there a standard producers work to or not. LFE is always 10db hotter than the normal channels for movie playback, but is this the case for SACD, DVDA, or digital 5.1 music DVDs. I think that is the question that needs answering, once you know the answer to that, you will know if your .1 channel needs augmentation for music playback, dependant on how each device works and handle such content. I am not sure if any players could tell the difference between a movie or music in a .1 encoded soundtrack, which would suggest they wouldnt be able to apply a 10db cut etc, unless something on that soundtrack was encoded to tell the device the relevant info. If that doesnt happen, its back to the first question above, is digitally recorded music with a discrete .1 channel produced with the .1 channel hot the same as it is in movie soundtracks.

 

[Mark.Yudkin]

How does this relate to the LFE on a 5.1 DTS Audio disc? There's a note in my Denpn amp which says the LFE must be reduced by 10dB if playing DTS music, but not films. Is it expected that the LFE is boosted and cut manually whenever different music source material is played (i.e. SACD vs DTS?).

The OP asked about SACD, so that's what I explained.

Dolby (please bear with me, I'm coming to dts) had a clear specification too: 10dB attenuation during mastering and boost during replay. Hence no user controlled switches are needed.

DTS is a different story - in simple terms, they "messed up". This fantastic old article explains it. The short version is that although most DTS tracks are attenuated, some, expecially older ones, aren't. As a result the listener needs a switch to be able to disable the 10dB boost on DTS for those occasional cases where it's not needed.

A 5.1 dts audio disk is in fact a perfectly normal DVD-V with a dts track and there are no additional considerations on the LFE. The CD version is simply a DC data disk with a file containing a dts-encoded audio track, and there are no additional considerations on the LFE.

 

[Mark.Yudkin]

This really begs the question as to how the discrete .1 channel is dealt with for music content. Is there a standard producers work to or not. LFE is always 10db hotter than the normal channels for movie playback, but is this the case for SACD, DVDA, or digital 5.1 music DVDs. I think that is the question that needs answering, once you know the answer to that, you will know if your .1 channel needs augmentation for music playback, dependant on how each device works and handle such content. I am not sure if any players could tell the difference between a movie or music in a .1 encoded soundtrack, which would suggest they wouldnt be able to apply a 10db cut etc, unless something on that soundtrack was encoded to tell the device the relevant info. If that doesnt happen, its back to the first question above, is digitally recorded music with a discrete .1 channel produced with the .1 channel hot the same as it is in movie soundtracks.

The answers to your question for SACD are post #4. DVD-A is the same as SACD, so just read "SACD and DVD-A" in post #4. The answer for DD and dts on DVD-V is in post #9.

Knowing if a disk contains music or movie is irrelevant, the standards are as per the disk's ostensible usage. An SACD of an opera has no boost, a DVD-V of the same opera has an LFE boost (dts special case as per post #9, independent of content).

 

[Mr Incredible]

The OP asked about SACD, so that's what I explained.
....

I know! I have a Denon DVD-2900 that can play SACD and DVD-A. I've got a Blue Man Group DVD-A on which there is DD 3/2.1, DTS 5.1 and "DVD-A". Got a couple of SACD's as well as a few music DVD's, some of which have DD or DTS outputs. All a bit confusing as to whether the .1 was mixed in at all and whether it needs cooling down or not!

Thanks for your explanation though. I think I'll have to find a darkened room and a wet towel compressed about my head to fully understand the nuances/implications!

 

[Mark.Yudkin]

I know! I have a Denon DVD-2900 that can play SACD and DVD-A. I've got a Blue Man Group DVD-A on which there is DD 3/2.1, DTS 5.1 and "DVD-A". Got a couple of SACD's as well as a few music DVD's, some of which have DD or DTS outputs. All a bit confusing as to whether the .1 was mixed in at all and whether it needs cooling down or not!

Thanks for your explanation though. I think I'll have to find a darkened room and a wet towel compressed about my head to fully understand the nuances/implications!

On disk, SACD and DVD-A are "flat", DD is attenuated, dts is probably attenuated (and a 10dB difference is so huge you can't possibly not hear if it's 10dB too much). The real question is what your DVD-2900 does with SACD and DVD-A, and the best answer I've found is here.

 

[Member 639844]

On disk, SACD and DVD-A are "flat", DD is attenuated, dts is probably attenuated (and a 10dB difference is so huge you can't possibly not hear if it's 10dB too much). The real question is what your DVD-2900 does with SACD and DVD-A, and the best answer I've found is here.

It would be much easier if these formats were simply encoded as .0 or .1, with the .1 being LFE boosted and the .0 not being. Low frequencies in a full HT system utilising bass management and 'proper' crossover setting would simply redirect low frequency bass anyway where one is present. In systems without subs the speakers would simply get all the content anyway, as in 2 channel hifi systems, and 2 channel hi-fi systems running subs via high level connection methods. That would make the entire process so much simpler and confusion free, and non of the settings used for compensation would even be necessary.

 

[Mark.Yudkin]

It would be much easier if these formats were simply encoded as .0 or .1, with the .1 being LFE boosted and the .0 not being. Low frequencies in a full HT system utilising bass management and 'proper' crossover setting would simply redirect low frequency bass anyway where one is present. In systems without subs the speakers would simply get all the content anyway, as in 2 channel hifi systems, and 2 channel hi-fi systems running subs via high level connection methods. That would make the entire process so much simpler and confusion free, and non of the settings used for compensation would even be necessary.

Well, whether .0 is boosted or not makes no difference .

But more importantly your argument misses the point as it's confusing the subwoofer output with the LFE channel. The relationship is tenuous at best.

The .1 channel on the carrier is an LFE channel, not a bass channel. Misuse of the LFE channel for the wrong purpose is a fact of life, but nevertheless remains abject abuse.

The low frequency effects - the channel that's supposed to give you the bangs, crashes and wallops of buildings crashing, animals stampeding, cities earthquaking or spacecrafts launching - can support higher SPLs without damaging your hearing, in order to shake your walls, furniture and butt. Hence the usage of level compression during mastering and boosting during replay, primarily to obtain greater headroom. This is of course inapplicable to music and hence inapplicable to formats targetted at music, this also explains why classical music CDs are typically 5.0, not 5.1 - there are no LFE instruments!

An important but distinct consideration is that domestic setups don't generally run full range speakers all round. No problem, we have a sub, so our digitial audio processing can simply redirect the bass away from the "small" speakers, mixing it with the LFE channel and directing the whole lot to the subwoofer. This is of course purely replay functionality.

The settings for compensation arise from two different issues. One, the main one, is confusion amongst content creators in the early days as to whether dts required LFE attenuation / boosting (DD was always clear); for this there is no workaround and none is possible. The other is our insistence on doing the decoding in some central unit that does not know what it's supposed to be doing, as opposed to doing it in the player, which does know. For example the Bluray creators did their best to ensure that HD decoding was carried out solely in the player, but the market players (those trying to sell receivers by adding functions) refused to abide. Most players universally normalize the .1 output at .10dB to ensure consistency, but some do not.

Incidentally, check the equal loudness countours:

 

[Member 639844]

I am well aware of the distinction between discrete .1 LFE bass and redirected bass. My point is, music should simply do away with trying to use the LFE and stick to re-directed bass only as this isnt boosted, which is what is wanted for music. That would scrub out any issues with regards to misuse of the LFE channel, or in this case, confusion between the guys producing the SACD music and the processor programmers, where non seem to know if they should be compensating for the other or not.

 

[Mark.Yudkin]

My point is, music should simply do away with trying to use the LFE and stick to re-directed bass only as this isnt boosted, which is what is wanted for music. That would scrub out any issues with regards to misuse of the LFE channel, or in this case, confusion between the guys producing the SACD music and the processor programmers, where non seem to know if they should be compensating for the other or not.

Although SACD permits 5.1, most are 5.0. Not that this makes the slightest difference in this context. As far as SACD is concerned there is no "confusion between the guys producing the SACD music and the processor programmers, where non seem to know if they should be compensating for the other or not". The rules are absolutely clear and always have been - there is no attenuation on SACD's .1 channel, and nobody needs to compensate for anybody else as all involved have nothing to do.

The case in which confusion arose was dts and that's why the feature is generally labelled "DTS LFE Gain" or "DTS LFE Boost" - to make it clear that it's a dts problem, and only a dts problem, affecting a small number of early DVD-V's.

Analogue replay - the subject of this thread - adds another, different confusion, that is independent of the level of the LFE / .1 channel. The possible dts LFE override setting is required on the player, so can be ignored here. With players offering internal bass management and analogue output for both DVD-V and SACD, the discrepancy in the norms between DVD-V and SACD became relevant when the analogue connectivity preventing the processor from determining if the source was DVD-V or SACD. So the user is forced to make a manual selection on the processor. This is of course independent of the question of LFE attenuation, or of whether the SACD even has a .1 channel, as the subwoofer channel is anyway mixed from LFE and redirected bass. DVD-V's need for 115dB meant that a 10dB attenuation was required on the LFE channel (full peak swing 105dB), and DVD players typically maintained the LFE attenuation on the .1 channel's analogue output. The processor therefore restores the 10dB ("DVD-A/SACD/MCH sub level") setting. SACDs 105dB max meant that no attenuation was required.

To alleviate the operational complexity, most players simply attenuate the subwoofer channel (subwoofer channel - not LFE) by 10dB on SACD replay to achieve consistent levels. The OP's question concerned this issue, and his player is one of those that attenuates the analogue subwoofer output on SACD replay.

One could argue that it would have been better if SACD had also had a 10dB attenuation on the .1 channel. One could also argue that it would have been better if the analogue outputs of a DVD player had never been attenuated (and processors therefore defined to support the higher maximum levels of the analogue subwoofer channel). Both approaches would have resolved the issue. However, it's now too late to change the specifications.