Stereo subs with XMC-2

[matyst]

@keithl - XMC-1 allowed L+R subs to be configured in stereo mode - on XMC-2 the options are only Mono or Dual Mono - what happened to the stereo mode ?
Is it possible to restore this functionality ?

Tomasz

[Talley]

ideally you would want dual mono regardless

[theswede]

Dec 9, 2019 16:07:51 GMT -5 Talley said:

ideally you would want dual mono regardless

Why would you want that?

[Lsc]

Nov 29, 2019 7:41:57 GMT -5 matyst said:

@keithl - XMC-1 allowed L+R subs to be configured in stereo mode - on XMC-2 the options are only Mono or Dual Mono - what happened to the stereo mode ?
Is it possible to restore this functionality ?

Tomasz

I would also like to have stereo when I’m listening to music.

I don’t want to go from the XMC2 to the Sub and back out to the power amp.

This would be fine for music but then I’ll need to rewire the sub when I watch movies.

[KeithL]

Dolby only calls for supporting a single LFE channel - as multiple-mono subs.

This remains the case with the new Dolby Atmos licensing.

On the XMC-1 we chose to offer an additional optional stereo sub mode.

However, at least initially, our new processors only support the options mandated by Dolby.

We do plan to eventually include that option on the RMC-1 / RMC-1L / XMC-2.

(I don't have a time frame for that yet.)

Dec 12, 2019 11:48:31 GMT -5 Lsc said:

Nov 29, 2019 7:41:57 GMT -5 matyst said:

@keithl - XMC-1 allowed L+R subs to be configured in stereo mode - on XMC-2 the options are only Mono or Dual Mono - what happened to the stereo mode ?
Is it possible to restore this functionality ?

Tomasz

I would also like to have stereo when I’m listening to music.

I don’t want to go from the XMC2 to the Sub and back out to the power amp.

This would be fine for music but then I’ll need to rewire the sub when I watch movies.

[donh50]

I have gone back and forth on stereo subs over many years (since ~1979/1980 when I built my first sub) and ultimately decided it is not worth it. It limits placement and correction options, almost no stereo content exits at sub frequencies (remember a wavelength is >11 feet at 100 Hz, >22 feet at 50 Hz, just how much stereo separation can there be in a normal listening situation?), and the end result was always much better when I ran the subs mono and placed them optimally for best in-room bass response. If your crossover is so high and/or filter roll-off so low that your subs intrude into the lower midrange you might appreciate stereo but I have always rolled off well below the point at which I could localize the subs. For years I ran stereo subs but many tests blind and otherwise convinced me stereo subs are just an unnecessary hassle that actually reduced my system's performance and sound.

YMMV - Don

[Lsc]

Dec 12, 2019 15:15:37 GMT -5 donh50 said:

I have gone back and forth on stereo subs over many years (since ~1979/1980 when I built my first sub) and ultimately decided it is not worth it. It limits placement and correction options, almost no stereo content exits at sub frequencies (remember a wavelength is >11 feet at 100 Hz, >22 feet at 50 Hz, just how much stereo separation can there be in a normal listening situation?), and the end result was always much better when I ran the subs mono and placed them optimally for best in-room bass response. If your crossover is so high and/or filter roll-off so low that your subs intrude into the lower midrange you might appreciate stereo but I have always rolled off well below the point at which I could localize the subs. For years I ran stereo subs but many tests blind and otherwise convinced me stereo subs are just an unnecessary hassle that actually reduced my system's performance and sound.

YMMV - Don

Oh so maybe it’s a non-issue.

I just got my 2nd sub so for now I’m using REW and have them in mono mode / dual mono

[Gary Cook]

Dec 12, 2019 15:15:37 GMT -5 donh50 said:

I have gone back and forth on stereo subs over many years (since ~1979/1980 when I built my first sub) and ultimately decided it is not worth it. It limits placement and correction options, almost no stereo content exits at sub frequencies (remember a wavelength is >11 feet at 100 Hz, >22 feet at 50 Hz, just how much stereo separation can there be in a normal listening situation?), and the end result was always much better when I ran the subs mono and placed them optimally for best in-room bass response. If your crossover is so high and/or filter roll-off so low that your subs intrude into the lower midrange you might appreciate stereo but I have always rolled off well below the point at which I could localize the subs. For years I ran stereo subs but many tests blind and otherwise convinced me stereo subs are just an unnecessary hassle that actually reduced my system's performance and sound.

YMMV - Don

Much the same here, I've been running 2.1 for stereo music for 40+ years and, having tried 1/2/3/4 subs, I keep coming back to 1. The current sub, best sounding to date, is sizeable (ported 140 litres) and has a decent Class A/B amp driving it, unlikely to change that opinion any time soon.

Merry Xmas
Gary

[Deleted]

Dec 12, 2019 15:15:37 GMT -5 donh50 said:

I have gone back and forth on stereo subs over many years (since ~1979/1980 when I built my first sub) and ultimately decided it is not worth it. It limits placement and correction options, almost no stereo content exits at sub frequencies (remember a wavelength is >11 feet at 100 Hz, >22 feet at 50 Hz, just how much stereo separation can there be in a normal listening situation?), and the end result was always much better when I ran the subs mono and placed them optimally for best in-room bass response. If your crossover is so high and/or filter roll-off so low that your subs intrude into the lower midrange you might appreciate stereo but I have always rolled off well below the point at which I could localize the subs. For years I ran stereo subs but many tests blind and otherwise convinced me stereo subs are just an unnecessary hassle that actually reduced my system's performance and sound.

YMMV - Don

Don hit it right on the nose!   Excellent post!

Let me repeat the important part and exception to mono subs in Don's post:
"If your crossover is so high and/or filter roll-off so low that your subs intrude into the lower midrange you might appreciate stereo"

"I have always rolled off well below the point at which I could localize the subs"    This is the case in quality systems with quality sub(s).

[Lsc]

I set one sub to mono and the other to LFE and it looks like only the “mono” sub is active for music and both are active for movies.

The PB16-ultra is more than enough for music by itself and there is no weird suck out. The SB13-plus is also more than capable for music actually. But the key as you guys are suggesting, running both of them at the same time sounds worse for music as I am unable to dial it in.

Seems like this is a pretty good compromise. Will test movies tomorrow as it’s too late.

[Hughes, G D]

Dec 12, 2019 12:13:40 GMT -5 KeithL said:

Dolby only calls for supporting a single LFE channel - as multiple-mono subs.

This remains the case with the new Dolby Atmos licensing.

On the XMC-1 we chose to offer an additional optional stereo sub mode.

However, at least initially, our new processors only support the options mandated by Dolby.

We do plan to eventually include that option on the RMC-1 / RMC-1L / XMC-2.

(I don't have a time frame for that yet.)

Dec 12, 2019 11:48:31 GMT -5 Lsc said:

I would also like to have stereo when I’m listening to music.

I don’t want to go from the XMC2 to the Sub and back out to the power amp.

This would be fine for music but then I’ll need to rewire the sub when I watch movies.

So, with a pair of subs from the left and right XLR sub outputs and the XMC2 set to Dual-Mono, Base management totals all audio below the filter, let's say 80hz, to both subs equally  and not as summed from left and right to left and right respectively?

[markc]

Correct. Both Subwoofers receive the same signal of LFE+summed-bass(all other channels below the chosen crossovers)

The subwoofer outputs are labelled Left and Right, so could in the future be configured to receive stereo bass as per the XMC-1 and as per KeithL post above, but this must be a niche market I'd say.

[Hughes, G D]

May 6, 2020 3:36:51 GMT -5 markc said:

Correct. Both Subwoofers receive the same signal of LFE+summed-bass(all other channels below the chosen crossovers)

The subwoofer outputs are labelled Left and Right, so could in the future be configured to receive stereo bass as per the XMC-1 and as per KeithL post above, but this must be a niche market I'd say.

So, that's why they refer to it with a 1 as in 9.1.6? Because although you can run 3 subs they are all just a single mono channel?

[markc]

May 6, 2020 5:14:27 GMT -5 Hughes, G D said:

May 6, 2020 3:36:51 GMT -5 markc said:

Correct. Both Subwoofers receive the same signal of LFE+summed-bass(all other channels below the chosen crossovers)

The subwoofer outputs are labelled Left and Right, so could in the future be configured to receive stereo bass as per the XMC-1 and as per KeithL post above, but this must be a niche market I'd say.

So, that's why they refer to it with a 1 as in 9.1.6? Because although you can run 3 subs they are all just a single mono channel?

Not quite.
As ever it gets far more complicated depending what you are referring to!
Indeed, the XMC-2/RMC have 9.3.4 outputs (Which can be reconfigured to be 9.1.6 as below)


When applied to content, the .1 refers to the number of LFE signal channels. Dolby and DTS only supply codecs that specify one LFE signal channel as far as I am aware, so the LFE input signal is always .1, so one mono channel.

(Incidentally this .1 LFE signal always requires a +10dB boost in the processor to play at the correct volume as the LFE signal is attenuated by 10dB so that when decoded and boosted it gives the 115bd headroom needed for bass impact in movies) (The other satellite/main channels have 105dB headroom by definition)

When applied to Surround Sound Processors, the 9.x.6 refers to output channels and in the RMC/XMC-2 can be up to 9.3.4 / 9.1.6*, or 7.1.2 etc depending on how many speakers and subs you have and configure within the SSP.


Surround Sound Processors like the XMC-2/RMC can distribute this single LFE signal to 0,1,2,3 or more subwoofers and generate from x.0.y (with zero subwoofers, where the LFE is mixed into any main channels set as "Large" speakers or discarded if all channels are "small") to x.3.y and up
(The LFE has the 10dB boost applied and is then summed with diverted bass from any and all "small" speaker channels to form the Subwoofer channel signal which is then sent to the 1 to 3 subwoofer outputs as identical mono signals)


So, The XMC-2/RMC can be 9.3.4 but the 3 subwoofers are all the same signal and mono.

The XMC-1 has an additional option where although it only has two subwoofer outputs, they can be set to dual mono or stereo. That was what was asked about in the original post for the newer processors.

On the XMC-1, 7.2 output could either be 7 channels plus two identical subwoofer mono channels OR 7 channels plus two stereo subs consisting of one left sided subwoofer signal containing LFE(with a 10db boost) summed with redirected bass from the left front, left surround and left rear plus a -3db attenuated centre channel redirected bass then a right sided subwoofer signal containing LFE(with a 10db boost) summed with redirected bass from the right front, right surround and right rear plus a -3db attenuated centre channel redirected bass . Both are designated 7.2 output.
(the -3dB attenuated centre bass halves the signal power to split the redirected centre channel bass to left and right without increasing the volume)

* NB if you have all 6 height / ceiling channels then you have to sacrifice the left and right subwoofer outputs on the XMC-2/RMC as they are repurposed to the extra two height channels.
If you have multiple subs you could daisy chain or use Y-cables to the multiple subs to get around this and the the internal DIRAC will not be able to measure and filter each sub independently, but only the sum of their outputs. (I don't want to start the incredibly complex issue of correcting for multiple subs here!)

[marcl]

May 6, 2020 5:56:31 GMT -5 markc said:

May 6, 2020 5:14:27 GMT -5 Hughes, G D said:

So, that's why they refer to it with a 1 as in 9.1.6? Because although you can run 3 subs they are all just a single mono channel?

Not quite.
As ever it gets far more complicated depending what you are referring to!
Indeed, the XMC-2/RMC have 9.3.4 outputs (Which can be reconfigured to be 9.1.6 as below)


When applied to content, the .1 refers to the number of LFE signal channels. Dolby and DTS only supply codecs that specify one LFE signal channel as far as I am aware, so the LFE input signal is always .1, so one mono channel.

(Incidentally this .1 LFE signal always requires a +10dB boost in the processor to play at the correct volume as the LFE signal is attenuated by 10dB so that when decoded and boosted it gives the 115bd headroom needed for bass impact in movies) (The other satellite/main channels have 105dB headroom by definition)

When applied to Surround Sound Processors, the 9.x.6 refers to output channels and in the RMC/XMC-2 can be up to 9.3.4 / 9.1.6*, or 7.1.2 etc depending on how many speakers and subs you have and configure within the SSP.


Surround Sound Processors like the XMC-2/RMC can distribute this single LFE signal to 0,1,2,3 or more subwoofers and generate from x.0.y (with zero subwoofers, where the LFE is mixed into any main channels set as "Large" speakers or discarded if all channels are "small") to x.3.y and up
(The LFE has the 10dB boost applied and is then summed with diverted bass from any and all "small" speaker channels to form the Subwoofer channel signal which is then sent to the 1 to 3 subwoofer outputs as identical mono signals)


So, The XMC-2/RMC can be 9.3.4 but the 3 subwoofers are all the same signal and mono.

The XMC-1 has an additional option where although it only has two subwoofer outputs, they can be set to dual mono or stereo. That was what was asked about in the original post for the newer processors.

On the XMC-1, 7.2 output could either be 7 channels plus two identical subwoofer mono channels OR 7 channels plus two stereo subs consisting of one left sided subwoofer signal containing LFE(with a 10db boost) summed with redirected bass from the left front, left surround and left rear plus a -3db attenuated centre channel redirected bass then a right sided subwoofer signal containing LFE(with a 10db boost) summed with redirected bass from the right front, right surround and right rear plus a -3db attenuated centre channel redirected bass . Both are designated 7.2 output.
(the -3dB attenuated centre bass halves the signal power to split the redirected centre channel bass to left and right without increasing the volume)

* NB if you have all 6 height / ceiling channels then you have to sacrifice the left and right subwoofer outputs on the XMC-2/RMC as they are repurposed to the extra two height channels.
If you have multiple subs you could daisy chain or use Y-cables to the multiple subs to get around this and the the internal DIRAC will not be able to measure and filter each sub independently, but only the sum of their outputs. (I don't want to start the incredibly complex issue of correcting for multiple subs here!)

I have had the occasional rant against the idea of stereo subs for the reasons already discussed, but as has been mentioned it could make sense if you need to cross your subs higher than 80Hz for smaller surrounds or center.  I happen to have this situation as I have surrounds/tops that cross at 100-130Hz and a Magnepan CC5 center that has to cross at 200Hz.  Yes, the center is mono but the idea is you may want to use broader range sub/woofers for music (as I use Magnepan DWMs).

The new processors have the option to send LFE ONLY to the Center sub output and bass management ONLY to the Left or Left+Right subs.  (poorly named, BTW, since they are not ever stereo).   Anyway...... if you set the Center Subwoofer to LFE, and set the Left/Right Subwoofers to None, and set the Left/Right Front speakers to Large .... does bass management go to the Left/Right Front speakers in stereo?  If so, you could have Left/Right subs connected to the Left/Right Fronts and get what we would properly call "Stereo Bass Management".  The Left/Right subs would have crossovers set to the lower limit of the Left/Right Front speakers (likely 40Hz or so) and you would get very good music bass down to that point and the subs would only play the rare sub-40Hz music content.

EDIT:   I figured a way to test this with REW tone generator.    With Center Sub=LFE, L/R Subs=None, L/R Fronts=Large .... bass management from other speakers is sent to L/R Fronts in mono. Also, Enhanced Bass option disappears, and nothing is sent to the Center Sub output.  So you don't get stereo subs but this behavior is what one would expect and is actually useful for those who don't want subs to play with music.  And if you play multichannel music with smaller surrounds that need bass management.

[NicS]

As Keith knows, I've asked for the addition of the ability to configure stereo subwoofers, specifically for digital music.

I have the following setup:
Front speakers: ATC SCM100 ASL active speakers x 3 (LCR)
Front Subwoofers: SVS PC12+ x 2
Rear Surrounds: ESS AMT1D x 2
Overheads: Definitive Audio UIW RCS III x 4
Processor: RMC1L
Power Amp: XPA 8-6-1s

For Phono I use Reference Stereo mode ( no need for the subs - phono struggles down that low and the ATCs sound just great without the subs)
For digital music I use Direct mode, activating the subs, crossing over at 50hz
For SACD - that just kicks straight into DSD mode so no issues there, either stereo or multichannel.
For Atmos Music - that same as SACD, it's just auto configured.

Having the option to have Stereo subs on Direct mode allows the speakers to better integrate with the subs. I position the subs very close to the L & R main speakers. When I had the XMC-1, this was by far the best sounding position for the subs, making them disappear into the sound of the mains. If I switched from Stereo subs to dual mono subs on my XMC-1, the sound was not as goof. The bass in some tracks was overstated and in other parts understated. It also lacked focus in the soundstage. The stereo sub option was far superior, just in this one mode.

When I upgraded to the RMC-1L I looked at other processor options simply because of the lack of the Stereo sub option in the RMC1-L. Keith has told e before that this option is certainly on the table, though there is no timeframe.

I wanted to put my name to this discussion as one person who has tested in his own system the sound of both stereo and dual-summed-mono sub options and categorically prefer the stereo option, for digital stereo music with deep bass extension. I'm talking Aleksi Perälä levels of bass here.

[hsamwel]

I’m a little skeptic of the stereo sub option. It’s almost like the REL high level
connection.
Also with the separate LFE sub option.

How could a single (or more subs) sound better than all together & calibrated?
Why would you want to separate LFE and bass management?
Or why would you want to have LFE from one sub in the room with all the
issues it creates?

Properly setup subs close to the front speakers disappears even in dual mono.
How could you ever get the even bass that two or more subs together creates
in the room when running them in ”single” mode?

I think it’s more how you place and setup your subs that’s important.
But maybe I’m missing something here that someone can enlighten me..

[rswood]

As Markc said above "(Incidentally this .1 LFE signal always requires a +10dB boost in the processor to play at the correct volume as the LFE signal is attenuated by 10dB so that when decoded and boosted it gives the 115bd headroom needed for bass impact in movies) (The other satellite/main channels have 105dB headroom by definition)"

Would you want a 10db bass boost to music only playback if all subs are summed with LFE?

[thezone]

Dec 13, 2019 2:45:29 GMT -5 Lsc said:

I set one sub to mono and the other to LFE and it looks like only the “mono” sub is active for music and both are active for movies.

The PB16-ultra is more than enough for music by itself and there is no weird suck out. The SB13-plus is also more than capable for music actually. But the key as you guys are suggesting, running both of them at the same time sounds worse for music as I am unable to dial it in.

Seems like this is a pretty good compromise. Will test movies tomorrow as it’s too late.

Took me  a while to get my head around this but I find connecting 1 sub as LFE and 1 sub as Bass management duties works well. You are correct, in this configuration, for music that does not contain a .1 dedicated channel the LFE sub will be silent and the Mono sub will be used for bass management, for movies the LFE channel receives its dedicated .1 track and the Mono sub will be used for bass management. If you want to use both subs for bass management when listening to music you could use preset 2 and set both subs as mono. 

This makes sense to me as the there would be differing material mixed into the LFE track than that mixed into all other speakers so why send all of that information mixed together to one sub to handle? Someone might disagree but I think as lower frequencies are the most difficult to reproduce breaking these differing low frequency signals among multiple subs makes sense.

I take this one step further and use an external cross over to divide that signal between multiple subs, so each sub array has 2 subs, a large one that receives 15-60 hz and a smaller sub that receives 60-90hz. I find this has more impact and a tighter bass than juts using a single sub. 

[thezone]

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