AVR Bass Management Question

[jcmccorm]

Hi folks, I have a question that I haven't seen discussed or answered anywhere yet.

For an AVR with 7 bed-layer channels with speakers all set to "small", all content existing under the crossover frequency for all channels gets summed, along with the LFE channel, and routed to the subwoofer output.

If the low frequency content for all channels (content under the crossover frequency) in the source is near 0dBFS in level (maximum level), how does the AVR avoid clipping the subwoofer output (exceeding 0dBFS) after summing all of the channels plus LFE?

Do all manufacturers handle this the same way?

Thanks in advance!

 

[Oddball]

You should not be stressed as we do acknowledge your concerns and appreciate your engagement. We are here to solve the problems so hang in there.

But to be certain we can assist you, we would need some further details about your system. You can for sure appreciate your issue and can be assured that your information will be handled in accordance with the privacy policy.

Not all manufacturers are likely to approach this serious issue in the same way so it might be helpful to understand your particular concern.

I hope that this post helped, but please do not hesitate to ask more questions if you need more help.

 

[antcollinet]

You should not be stressed as we do acknowledge your concerns and appreciate your engagement. We are here to solve the problems so hang in there.

But to be certain we can assist you, we would need some further details about your system. You can for sure appreciate your issue and can be assured that your information will be handled in accordance with the privacy policy.

Not all manufacturers are likely to approach this serious issue in the same way so it might be helpful to understand your particular concern.

I hope that this post helped, but please do not hesitate to ask more questions if you need more help.

WTF?

 

[Oddball]

WTF?

I swallowed a bot pill? Big mistake? But the point still valid - we need more info.

 

[Oddball]

I guess you guys are having a hard time accomodating to a new syntax and approach? Absolutely nothing wrong with what I have said. How is a different matter.

 

[voodooless]

how does the AVR avoid clipping the subwoofer output (exceeding 0dBFS) after summing all of the channels plus LFE?

It’s relatively easily to do: you just lower the gain of the channels, so that with perfect summing you would not reach 0 dBFS.

LFE channels are already encoded 10 dB hotter, so there basically is already a 10 dB headroom.

Which makes a lot of sense if you think about the fact that a single sub should reproduce the bass of multiple speakers. It has te be able to deliver some mighty power! 10x more power is fairly conservative in many cases.

 

[antcollinet]

I swallowed a bot pill? Big mistake? But the point still valid - we need more info.

OK - but we have a new member here. Your post came across to me as unfriendly / unwelcoming. I'm sure that is not what you intended, but that's how it came across.


In any case, the question to me is clear - I even started to answer it then realised I am not sure of my understanding myself - so stopped.

Id be more than interested to hear from anyone who can explain more clearly than I can why this is not an issue to worry about - or how it is managed in the AVR.

 

[antcollinet]

It’s relatively easily to do: you just lower the gain of the channels, so that with perfect summing you would not reach 0 dBFS.

But presumably only the gain of the summed bass. And then (hopefully) only as much as is needed for the levels of bass at the time - otherwise for a 9 channel +LFE system you'd be turning down the bass of everything by around 20dB, relative to the non bass.

But then you'd also need some form of "bass level gain tracking" for when the levels of bass go up or down.


Or is it just some form of dynamic compression.


It is far from clear to me how this is made to work without messing up the tonal balance.


EDIT - or the digital bass channel is given 20dB of headroom compared with the individual channels - this would make far more sense to me. Turn down the digital gain, then turn it up by the same amount in the analogue domain - even if that analogue gain up is done with the sub's own gain dial.

 

[voodooless]

But presumably only the gain of the summed bass. And then (hopefully) only as much as is needed for the levels of bass at the time - otherwise for a 9 channel system you'd be turning down the bass of everything by nearly 20dB, relative to the non bass.

But then you'd also need some form of "bass level gain tracking" for when the levels of bass go up or down.


Or is it just some form of dynamic compression.


It is far from clear to me how this is made to work without messing up the tonal balance.


EDIT - or the digital bass channel is given 20dB of headroom compared with the individual channels - this would make far more sense to me. Turn down the digital gain, then turn it up by the same amount in the analogue domain.

Read my edit, that should make it more clear

I think in reality ther might be more than that 10 dB headroom, especially if room correction is involved. And most likely the mixing of channels isn’t done with equal gain either. Most probably the main channels will have the least amount if negative gain, the rest quite a bit more. You’ll also have to take the channel gains into account that result from the calibration vs the subwoofer calibration.

 

[kyuu]

I guess you guys are having a hard time accomodating to a new syntax and approach? Absolutely nothing wrong with what I have said. How is a different matter.

There's a lot wrong with it. It reads like you're having AI do your posting for you. It was totally unhelpful, and wrong to boot. The OP's question was clear and we don't need more information for someone who understands the topic to answer.

My assumption is that this is handled at the mixing/mastering level; the bass in all the channels simply don't sum up to over 0dBFS. However, I would also be interested in hearing from someone who actually knows rather than making assumptions.

 

[Andysu]

WTF?

?

It’s relatively easily to do: you just lower the gain of the channels, so that with perfect summing you would not reach 0 dBFS.

LFE channels are already encoded 10 dB hotter, so there basically is already a 10 dB headroom.

Which makes a lot of sense if you think about the fact that a single sub should reproduce the bass of multiple speakers. It has te be able to deliver some mighty power! 10x more power is fairly conservative in many cases.

what ? what is hotter fully explain this in yt video ?

 

[antcollinet]

Read my edit, that should make it more clear

I think in reality ther might be more than that 10 dB headroom, especially if room correction is involved. And most likely the mixing of channels isn’t done with equal gain either. Most probably the main channels will have the least amount if negative gain, the rest quite a bit more. You’ll also have to take the channel gains into account that result from the calibration vs the subwoofer calibration.

Yep - that is the conclusion I reached in my own EDIT.


@jcmccorm is your question answered?

 

[antcollinet]

?

what ? what is hotter fully explain this in yt video ?

Allow me to summarise:


LFE channel is 'kin loud.

 

[voodooless]

what ? what is hotter fully explain this in yt video ?

Sorry, my mistake. It’s the other way around: it’s encoded 10 dB lower, and the processor brings that back again at playback. That just means that 0 dBFS of encoded LFE is 10 dB louder than the other channels.

 

[jcmccorm]

Haha! Long winded post here but bear with me.

First off, @Oddball, no offense taken by your post. My first thought was just like @antcollinet , "WTF?" Then I thought, cool, ASR has a bot named Oddball, and I love Kelly's Heroes Also, I hope I'm not offending you at all here, definitely no offense meant, your post just read kind of like something AI would write.

The question is generic which should apply to all AVRs/Prepro's, but I'll get specific and give context for my question.

The rabbit-hole started when I was listening to a new (to me) ATMOS music disc for the first time, Pink Floyd's "Animals". 25 minutes into it, in the song "Pigs", I heard some deep bass that sounded clipped. It sounded obviously "wrong". My first thought was that I've screwed something up in my gain structure for the subs. Checked that and the fact that I can turn down the MV really low and *still* hear it means that it's not me. So, it must be the source.

I ripped the Bluray and extracted WAV files (8 of them for 7.1). I examined the waveforms at the "bad" spot and there was no visible clipping. I ran RTA against the WAV files (using REW) and can clearly see the the offending tone is 17Hz. My subs are all sealed so there's no chance of port noise. (17Hz is close to where a lot of people tune their ported box to so a valid assumption would be port noise).

So it's not me, and I couldn't see anything in the source waveforms, so the only thing that I have ZERO visibility into is what the AVR is doing when it sums low frequency content from all bed-layer channels. Is it possible my AVR is clipping the sub output?

I'm using a Panasonic 820 player and the AVR is a Yamaha A8A. The connection between them is HDMI.

My understanding of the way the LFE channel is handled is that the mixer (source) attenuates the LFE by 10db and the AVR adds it back internally.

Let me go back and read all the responses over again. I didn't completely grasp it all so my question may indeed be answered. I didn't see anything beyond speculative answers (which is completely fine) but I need to understand it better so I can possibly test the theories somehow. (Really what I need is a way to mix my own 7.1 content with low-frequency test tones in all channels and view the analog preamp outputs with a 'scope to see what happened in the AVR).

 

[Andysu]

Allow me to summarise:


LFE channel is 'kin loud.

? do a yt video detail video to explain demo , this is asr , scientific

 

[voodooless]

Haha! Long winded post here but bear with me.

First off, @Oddball, no offense taken by your post. My first thought was just like @antcollinet , "WTF?" Then I thought, cool, ASR has a bot named Oddball, and I love Kelly's Heroes Also, I hope I'm not offending you at all here, definitely no offense meant, your post just read kind of like something AI would write.

The question is generic which should apply to all AVRs/Prepro's, but I'll get specific and give context for my question.

The rabbit-hole started when I was listening to a new (to me) ATMOS music disc for the first time, Pink Floyd's "Animals". 25 minutes into it, in the song "Pigs", I heard some deep bass that sounded clipped. It sounded obviously "wrong". My first thought was that I've screwed something up in my gain structure for the subs. Checked that and the fact that I can turn down the MV really low and *still* hear it means that it's not me. So, it must be the source.

I ripped the Bluray and extracted WAV files (8 of them for 7.1). I examined the waveforms at the "bad" spot and there was no visible clipping. I ran RTA against the WAV files (using REW) and can clearly see the the offending tone is 17Hz. My subs are all sealed so there's no chance of port noise. (17Hz is close to where a lot of people tune their ported box to so a valid assumption would be port noise).

So it's not me, and I couldn't see anything in the source waveforms, so the only thing that I have ZERO visibility into is what the AVR is doing when it sums low frequency content from all bed-layer channels. Is it possible my AVR is clipping the sub output?

I'm using a Panasonic 820 player and the AVR is a Yamaha A8A.

My understanding of the way the LFE channel is handled is that the mixer (source) attenuates the LFE by 10db and the AVR adds it back internally.

Let me go back and read all the responses over again. I didn't completely grasp it all so my question may indeed be answered. I didn't see anything beyond speculative answers (which is completely fine) but I need to understand it better so I can possibly test the theories somehow. (Really what I need is a way to mix my own 7.1 content with low-frequency test tones in all channels and view the analog preamp outputs with a 'scope to see what happened in the AVR).

Do you have any idea what the room correction does for the bass channel at those frequencies? Does the clipping stop if you lower the volume?

 

[antcollinet]

? do a yt video detail video to explain demo , this is asr , scientific

Well if YT is what makes it sciency for you I suppose I could make a video of myself saying "LFE is 'kin loud"


I could even shout it to emphasise the point if you like.

 

[voodooless]

Well if YT is what makes it sciency for you I suppose I could make a video of myself saying "LFE is 'kin loud"


I could even shout it to emphasise the point if you like.

Don’t forget to use a baritone voice!

 

[antcollinet]

Does the clipping stop if you lower the volume?

Or turn down the bass channel gain in the AVR (can be done in denon - I assume so in others). You can turn up your sub gain to compensate.


EDIT - also bear in mind it might not be clipping. That might just be what the bass sounds like - or it is possible it was clipped at some point in the recording/mastering process, and then later turned down to below 0dbFS