AVR Bass Management Question

[Tre2023]

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.

Yikes, that slab of meat needs a good rub and a proper grilling.

 

[Tre2023]

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).

Nice setup. What are your speaker configuration, speaker sizes and crossover settings? Do you have Yamaha’s infamous Extra Bass feature turned ON?

 

[popej]

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.

Do you have YPAO Volume on?

Edit: another thought.
Hearing is not very sensitive for distortion at low frequency. You probably won't notice even serious clipping from subwoofer. If you can hear it, then probably it comes from other channels. Try to listen near sub and speakers, to find where it comes from.

 

[jcmccorm]

Yikes, that slab of meat needs a good rub and a proper grilling.

Ok, that's just funny right there. Made my day.

My crossovers are set to 90Hz for the left/center/right, and 110Hz for the surround, rear surround and heights (7.2.4 system)
The speakers in the bed layer are all kits from DIY Sound Group (now Cinergy Audio). The left/center/right are these:

Denovo Audio Elusive-1099

Denovo Audio, Elusive 1099 speaker, DNA-205, SEOS waveguide, speaker kit

www.diysoundgroup.com

Even though each speaker up front has two 10" drivers for woofers, these things start to roll off at 70Hz so a subwoofer is definitely required.

Quick pic of the front wall. Not a dedicated Home Theater but my wife has let me get away with quite a bit with this room

Subs are all DIY. "My name is James and I have a bass problem". They just kind of keep growing. But I have discovered that the more cones/displacement you have, the less power they require to reach a certain SPL and the less distortion (less cone movement required). That's true, just not something that I keep telling myself

So up front are two 21" Eminence NSW6021 drivers in a 6cuft sealed enclosure. The pic is of 21" LaVoce's but I just replaced them with the NSW's.
Just behind the seating (where the picture is taken from) is eight 12" drivers and two 18" drivers all in sealed enclosures setup for near-field duty across four seats.
I use three NU6000 Class D amps to drive all that. It's still a work in progress but it does make me smile.

So you can imagine my surprise when I heard this weird bass sound when playing music. I've thrown a lot of movie demos through this system and it's always held up. Plus, since it's DIY, naturally I'm going to think that perhaps I did something wrong.

No Extra Bass turned on in the Yamaha. That was actually one of the first things I checked. I never turn that on but needed to check since that would definitely explain some things I was hearing if it was inadvertently turned on.

The NU6000 amps have LEDs in the front that show if the input is clipping and they are all off (it's an LED ladder) during this "bad passage" in the song. As far as the outputs, my listening level for music or movies is -26db to -22db on the Master Volume and the subs really aren't working hard at those levels.

Does anybody have this disc by chance that they could reproduce what I'm hearing? It's Pink Floyd so I thought that everyone would have this

I will continue to check out my subs for issues; I want to measure actual voltages coming out of the AVR, in and out of the DSP, and into and out of the amps. This will give me piece of mind that it's all ok.

Beyond that, this has got to be either some voodoo going on inside the AVR's bass management since it seems that we don't know how it prevents exceeding 0dBFS after summing all of that low-frequency content, or, just a weird mistake in the audio mix from the source.

 

[jcmccorm]

Do you have YPAO Volume on?

Edit: another thought.
Hearing is not very sensitive for distortion at low frequency. You probably won't notice even serious clipping from subwoofer. If you can hear it, then probably it comes from other channels. Try to listen near sub and speakers, to find where it comes from.

Thanks @popej. I have YPAO Volume off. I have run the YPAO calibration of course but since I have an external DSP ('miniDSP 2x4 HD') in the signal chain between the Yamaha and the amps, I removed all of the PEQ in the Yamaha for the subwoofer outputs and just rely on the miniDSP. I am using both sub outputs of the Yamaha, set to monaural, and their levels are both set to 0db (no gain, no attenuation).

Good idea on listening to individual speakers. I have not done that but will tonight. It will be helpful to narrow it down that way.

 

[Tre2023]

Very nice room. I have near identical paint on walls and trim with hardwood floors. Speaker and rug colors complement it all nicely.

Out of curiosity, have you ever experimented and moved the Fronts closer into the room and placed the subs under them?

 

[Miker 1102]

Ok, that's just funny right there. Made my day.

My crossovers are set to 90Hz for the left/center/right, and 110Hz for the surround, rear surround and heights (7.2.4 system)
The speakers in the bed layer are all kits from DIY Sound Group (now Cinergy Audio). The left/center/right are these:

Denovo Audio Elusive-1099

Denovo Audio, Elusive 1099 speaker, DNA-205, SEOS waveguide, speaker kit

www.diysoundgroup.com

Even though each speaker up front has two 10" drivers for woofers, these things start to roll off at 70Hz so a subwoofer is definitely required.

Quick pic of the front wall. Not a dedicated Home Theater but my wife has let me get away with quite a bit with this room

View attachment 520500


Subs are all DIY. "My name is James and I have a bass problem". They just kind of keep growing. But I have discovered that the more cones/displacement you have, the less power they require to reach a certain SPL and the less distortion (less cone movement required). That's true, just not something that I keep telling myself

So up front are two 21" Eminence NSW6021 drivers in a 6cuft sealed enclosure. The pic is of 21" LaVoce's but I just replaced them with the NSW's.
Just behind the seating (where the picture is taken from) is eight 12" drivers and two 18" drivers all in sealed enclosures setup for near-field duty across four seats.
I use three NU6000 Class D amps to drive all that. It's still a work in progress but it does make me smile.

So you can imagine my surprise when I heard this weird bass sound when playing music. I've thrown a lot of movie demos through this system and it's always held up. Plus, since it's DIY, naturally I'm going to think that perhaps I did something wrong.

No Extra Bass turned on in the Yamaha. That was actually one of the first things I checked. I never turn that on but needed to check since that would definitely explain some things I was hearing if it was inadvertently turned on.

The NU6000 amps have LEDs in the front that show if the input is clipping and they are all off (it's an LED ladder) during this "bad passage" in the song. As far as the outputs, my listening level for music or movies is -26db to -22db on the Master Volume and the subs really aren't working hard at those levels.

Does anybody have this disc by chance that they could reproduce what I'm hearing? It's Pink Floyd so I thought that everyone would have this

I will continue to check out my subs for issues; I want to measure actual voltages coming out of the AVR, in and out of the DSP, and into and out of the amps. This will give me piece of mind that it's all ok.

Beyond that, this has got to be either some voodoo going on inside the AVR's bass management since it seems that we don't know how it prevents exceeding 0dBFS after summing all of that low-frequency content, or, just a weird mistake in the audio mix from the source.

That is really nice looking and a great set up. Did you chamge any settings recently? You had stated it is a recent issue. I also wondered if you hear any audible difference with the center being low? I have been trying to figure out a different solution since downsizing.

 

[Chrispy]

Found something interesting from googling. "Bass Management and the LFE Channel" by Anthony Grimani (pretty sure that guys knows some things ) at Sound and Vision.

Bass Management and the LFE Channel

Bass is like salt. Really, it is. Salt is a seasoning, a treat that we add to good food to make it taste even better. Bass is the same way. A sound system without it lacks the last little element that transforms an ordinary activity like listening to music or watching a movie into an...

www.soundandvision.com

On page 2, he says this:

"There is NO NEED for an LFE channel in the vast majority of music applications. There continue to be multichannel music recordings released with content in the LFE channel when the bass in the main channels isn't even close to overload. Inexplicably, some music-recording engineers think that they must put something into the LFE channel so that end users will hear sound coming from their subwoofers.

Frankly, that's terrible logic because the subwoofers in bass-managed systems (which represent the overwhelming majority) receive the LFE channel and the sum of the main-channel bass. Users and installers of multichannel systems don't really need to worry about a music recording with an LFE channel as long as they set up their systems correctly with bass management. At times, however, bass-managed playback systems dig up bass that recording engineers didn't hear because their monitoring systems weren't bass-managed and their monitor speakers weren't full-range. This unmonitored bass sounds ultra-funky, and there's absolutely nothing users can do about it without reconfiguring their systems every time they switch discs. It's time for us to lodge some complaints with the production community!"

Interestingly, when viewing the waveforms from the Bluray in Audacity, the only activity I see in the LFE channel is where the "bad" sound is. So, speculating some more, I think that Anthony is saying that low frequencies from bed-layer channels will never clip when summed, but when the LFE is added, it could. Further, he blames the producer for this. So this could be what I'm hearing. It doesn't answer my question though about what the AVR is doing, but it makes me feel better knowing that someone in the industry has observed this phenomena.

What music actually uses LFE?

 

[jcmccorm]

What music actually uses LFE?

This disc does. I can see it in the LFE channel of the extracted WAV files. Pretty much nothing in the LFE channel until 25 minutes in when I hear this odd tone.

 

[jcmccorm]

That is really nice looking and a great set up. Did you chamge any settings recently? You had stated it is a recent issue. I also wondered if you hear any audible difference with the center being low? I have been trying to figure out a different solution since downsizing.

Thanks @Miker 1102! No settings change. Just recently got a new disc, Pink Floyd's "Animals" in ATMOS, and this disc is the first time I've come across this issue.
No issues with the center channel being low. I've tried it both above and below and I prefer it below. Obviously I'd rather have a projector and an acoustically transparent screen so I could place it right behind the center of the screen but this placement below, for me, is a minimal compromise. I *do* tilt the front of the center channel up so that it points directly at ear level (only one row of seating here).

 

[jcmccorm]

Very nice room. I have near identical paint on walls and trim with hardwood floors. Speaker and rug colors complement it all nicely.

Out of curiosity, have you ever experimented and moved the Fronts closer into the room and placed the subs under them?

The wide placement is technically a little too wide if I'm following the rule of "equilateral triangle" for left/right placement. My problem is that there's a hallway, then an office and a bathroom behind my screen wall that one of our live-in kids use for work-from-home. Those two openings on either side of the screen get used a lot so I didn't want the speakers in the way any more than they already are. That being said, the kids are in the process of moving into their own house and I'm currently building doors for those two openings so I'll get to try pulling the speakers in a bit towards the screen. I will still occasionally need to get past them so I'll need to figure out a way to move them easily. Oh and the other thing is that all the gear is directly on the back side of the screen wall, including the Bluray player, so I'll definitely need to get back there easily.

I'm building the doors so that I can see if I can get a little more room-gain out of the subwoofers by removing the big "suck-out" that those openings present. If I can get a couple more db at 20Hz and below for free (well, the cost and trouble of building custom doors) then it'll be a victory.

 

[Tre2023]

I’ve found that felt on the bottom of furniture and speakers sitting on hardwood floors makes things very easy to slide around and does not leave any marks on the floor.

Have you tried isolating the issue a bit more by setting all speakers to Large and using Pure Direct mode to play this particular album? The Subs will receive nothing but information contained in the LFE channel this way and you can compare your results to those using your Small speaker settings.

 

[jcmccorm]

I’ve found that felt on the bottom of furniture and speakers sitting on hardwood floors makes things very easy to slide around and does not leave any marks on the floor.

Have you tried isolating the issue a bit more by setting all speakers to Large and using Pure Direct mode to play this particular album? The Subs will receive nothing but information contained in the LFE channel this way and you can compare your results to those using your Small speaker settings.

Thanks @Tre2023, that's exactly what I intend to do next. Set all speakers to Large. If I suspect that there's some funny business going on in the AVR with summing bass from all the Small speakers, this will eliminate it. The subs will only get content from the discreet LFE channel.

 

[Tre2023]

Don't forget to play around with NET RADIO.

 

[Soundmixer]

We can be posting all day long what is mixed and how it is mixed and how it impacts our systems. If isolated to some tracks, probably best to ignore it.

Best way to avoid clipping in the low end is to have sufficient firepower for whatever your need, and have it reigned in with some decent EQ system that will also cater to your needs. If you have a +10dB bump in your sub range, it will likely clip if your subs are not good for that (aka 115dB reference + 10dB, plus whatever your bass curve might be - this could take you to 130+dB theritory).

My subs don't really clip as they have a DSP that avoids that - very grateful for that as did not know when I was buying them, or how important that might be for the bass heads.

The reference level of 115 dB with the sub and 105 dB with the mains is a theatrical reference, not a home-level reference. I have never mastered a track intended for the home environment at 85 dB, and neither has any other studio that I know of.

 

[Oddball]

The reference level of 115 dB with the sub and 105 dB with the mains is a theatrical reference, not a home-level reference. I have never mastered a track intended for the home environment at 85 dB, and neither has any other studio that I know of.

Well that is very interesting. I guess we could discuss that for next couple of years given the number of releases - which is not my intention. Obviously the sound level from different mixes is different depending on the mix. But what I also found out (since not using discs any more), is that some streaming services are just louder than the others, thus really altering the absolute sound levels of the mix.

I did get way north of 100dB peaks for the bass for random newer titles I tested at 0 reference. Older movies are not getting there even with +12dB ART shelf, or perhaps only for 1 or 2 peaks. Did not really measure the mains or subs separately as that tends to get difficult for ART setups.

 

[EWL5]

Well that is very interesting. I guess we could discuss that for next couple of years given the number of releases - which is not my intention. Obviously the sound level from different mixes is different depending on the mix. But what I also found out (since not using discs any more), is that some streaming services are just louder than the others, thus really altering the absolute sound levels of the mix.

I did get way north of 100dB peaks for the bass for random newer titles I tested at 0 reference. Older movies are not getting there even with +12dB ART shelf, or perhaps only for 1 or 2 peaks. Did not really measure the mains or subs separately as that tends to get difficult for ART setups.

I just saw a scene in Project Hail Mary that will absolutely wreck some speakers when released for home video.

 

[jcmccorm]

I got a chance to play the "bad" part of the track with all of my speakers set to "Large" instead of "Small" (small is my normal setting). I heard the 17Hz tone but it sounded fine; problem gone. The bass was thin of course since my speakers are not full range.

So I'm still not sure exactly what this means. Most likely it means that what Anthony Grimani stated in the article I posted above is true; the person mixing made a mistake by adding content into the LFE channel when using a monitor system without bass management and speakers that were not full range such that they could not hear the issue, just like I can't hear it with my speakers set to "Large".

The other possibility is that the AVR is doing something funny when bass management is engaged as a result of summing all of the low frequency content. To that end, I used Audacity to view the WAV files extracted from the disc but I don't know how to tell how the levels look on a dBFS scale (my thinking is that if all channels are recorded with some content close to 0dBFS, then there could be a problem for the AVR trying to apply bass management).

I do feel confident however that it isn't a "me" problem (meaning my gear ) and I'll just have to live with it.

 

[Tre2023]

Curious, any differences between Pure Direct, Straight or Auto/DSur when speakers are set to Large and playing that particular track?

 

[jcmccorm]

Good question, I didn't try it but I will. Had it on Auto so DSUR was engaged.

Does Pure Direct imply analog inputs or can you use that with an HDMI input as well? (never tried Pure Direct).