Stereo Sub Vs Dual Mono

[thcdru2k]

In my own adventures with calibrating, I have come to appreciate how tightly coupled placement, crossover region, and DSP strategy are in the low frequencies. Even relatively small changes in geometry, mechanical coupling, or measurement mic position can meaningfully alter what REW shows, particularly around deep nulls and modal peaks, which makes low frequency behavior highly location dependent. For that reason, I tend to treat stereo versus mono bass, crossover choices, and sub matrixing as room specific variables rather than starting with a strong preference for any single approach. I am still experimenting, but I try to let measurements steer my decisions instead of assuming that one topology is universally optimal. I have also found it invaluable to keep a simple journal so I can track what changes were made and what I actually observed each time I test a new variable, especially when using mixed feeds to the subs. It becomes even more complicated once you factor in the front speakers contribution in the bass region.

 

[「 ✦ JIM ✦ 」]

I have a sub beside each main running in mono crossed over with a Linkwitz Riley at 50hz and added some gain to liven things up a bit. Have a high pass on the mains. Was running stereo for a while but couldn't hear an advantage and considering I get a slightly different response at the LP from each sub due to the room, I kind of thought it was pointless. Maybe I will try again with a higher crossover but my mains have really great output higher up anyway.

 

[Bwaslo]

Isn't comparing two subs in mono to two subs with all the sub sound coming from one side the same as playing one mono sub? Essentially comparing whether two subs is better than one? No surprise that sounds different.

 

[dan_remaincalm]

1.How did you perform the mono-downmix @ 60hz ?

i initially used the "mono bass" button on the TDR SlickEQ M processor, but when I checked, I found that had stereo effects up into to 300Hz range

i settled on a chain using fabfilter pro-q 3 to do sub/main split at 48dB/oct, with one file having the sub component mono-ed (with appropriate level correction) and the other stereo. both test files went through the same processing to eliminate differences from the EQ.

this is the pan spectrum of a hard-left pink noise burst through the mono processor:

I did another test today at low volume levels to reduce the possibility of subwoofer distortion changing the audibility, and at that lower volume I got one of 18 trials wrong (94% correct). Still way above the science threshold though.

2.ABX only allows you to to determine if you can tell them apart, and we have already concluded that it is reasonable to expect that you can do that in your setup (or most dual sub setups) due to differences in how they excite room modes.

I don't think it's that. The left/right sub response at listening position is near-identical down to 35Hz - I've been tuning this space for about 12 years. These are 1/48 smoothing, the highest it'll go in waterfall view:

(the junk down under 30Hz is the classic SVS SB-1000 subsonic rumble btw, discussed elsewhere on this forum - I never got around to replacing the amps...)

Edit: here's the bass L/R phase as well to exclude that being a factor:

3.If you feel like you can reliably tell the difference and stereo subs overall sounds better to you, you should of course configure your subs in stereo.

 

[dan_remaincalm]

Isn't comparing two subs in mono to two subs with all the sub sound coming from one side the same as playing one mono sub? Essentially comparing whether two subs is better than one? No surprise that sounds different.

everything is level-matched by the processors - here's the mono-summed spectrum of the two test files (blue vs orange):

 

[Bwaslo]

Sure, but double subs in mono (and in different places) also provide diversity of the peaks and nulls from room effects, the effect is more than just turning the volume up on one sub.

 

[dan_remaincalm]

Sure, but double subs in mono (and in different places) also provide diversity of the peaks and nulls from room effects, the effect is more than just turning the volume up on one sub.

... did you see the separate L and R waterfall graphs i posted in #244? with a bunch of arsing around with treatment and DSP, it's absolutely possible to get ruler-flat bass response at a controlled listening position.

most rooms suck, so for the vast majority of setups with untreated rooms and consumer gear, multiple subs in mono overwhelmingly make a lot of sense. but aren't the folks on this forum aiming for the pinnacle of sound, within the constraints of measurement and science? i'm suggesting that on at least some systems, there are (ABX-able) huge subjective improvements to be had by not downmixing subs to mono, even without getting into that most subs are playing audible content up in the 150Hz range anyway.

...while i was writing this, i just stumbled on another kickass test track. beastie boys - ricky's theme, original cd version. it's an instrumental jazz track. it has two different drum kits panned hard L and R and a double bass panned hard right, with some different bass overdubs on the left. it sounds miraculous. if you've got a good full range setup that you can hard pan one direction or the other, it's worth a test.

 

[audiofooled]

did you see the separate L and R waterfall graphs i posted in #244? with a bunch of arsing around with treatment and DSP, it's absolutely possible to get ruler-flat bass response at a controlled listening position.

most rooms suck, so for the vast majority of setups with untreated rooms and consumer gear, multiple subs in mono overwhelmingly make a lot of sense. but aren't the folks on this forum aiming for the pinnacle of sound, within the constraints of measurement and science? i'm suggesting that on at least some systems, there are (ABX-able) huge subjective improvements to be had by not downmixing subs to mono, even without getting into that most subs are playing audible content up in the 150Hz range anyway.

This is essentially what I asked Floyd Toole in this thread, where his discussion with JJ and Thomas Lund in the nearby posts I find very interesting:

A Broad Discussion of Speakers with Major Audio Luminaries

Even though I know intellectually the challenges of creating the sensation of a large space using stereo speakers in a smaller room (mine is 13’ x 15’ with a large room opening to the hallway), in practice I have found I can get quite a believable-to-me sensation of listening into a very large...

www.audiosciencereview.com

I agree with your points, something I experimented myself, which ultimately lead to my preference for stereo bass. But also for me it is quite understandable why mono bass management is still a common strategy for most people and most rooms. Things get complex very quickly, IMO best described in the above thread and elsewhere on the forum.

 

[Birdy]

untreated rooms and consumer gear

My "untreated room and consumer gear" works great with my mono TL sub with DSP which is cut of at 40 Hz / 48 dB, super deep and room filling sub bass, no interfirence with my main speaker output at very low cost. This avoids lot's of problems by just filtering very steep at very low <40 Hz frequencies with DSP.

 

[goat76]

My subwoofers are placed symmetrically however the room is asymmetric and it is clear they excite the room differently. Not by design per say but due to wife approval constraints. It is nice however when wife approval coincidentally aligns with positive acoustic properties

Just like in your system, the subwoofers are set up symmetrically close outside each main speaker, but the whole setup is asymmetrically positioned more to one side in the room itself. The reason for that is that it feels and looks more natural with more open space on the side where the entrance to the room is.

The whole setup positioning of the system was done before I read David Griesinger's papers on bass envelopment, so the great result I’m experiencing in my listening room is basically just pure luck, as I’ve later on discovered that the placement of the speakers excites the room modes differently, similarly as Griesinger describes in his papers.

 

[JRowland]

Just like in your system, the subwoofers are set up symmetrically close outside each main speaker, but the whole setup is asymmetrically positioned more to one side in the room itself. The reason for that is that it feels and looks more natural with more open space on the side where the entrance to the room is.

The whole setup positioning of the system was done before I read David Griesinger's papers on bass envelopment, so the great result I’m experiencing in my listening room is basically just pure luck, as I’ve later on discovered that the placement of the speakers excites the room modes differently, similarly as Griesinger describes in his papers.

Sounds like I got lucky too, I have a very similar arrangement to you. When first deciding how to set my room up (long wall or short) I read a lot. I came across some folks in the business of getting paid to set things up who advocated for a little asymmetry if going long wall, and that was my preference for the view. I love feeling low frequencies (and all frequencies I can feel with some 85-95db volume) coming from left or right at times. My multichannel is very enveloping as well, I’m so happy I gave directional bass a try. I don’t feel like I miss a thing when the bass in the recording is mono, yet I get those feels when it is not.

 

[Flaesh]

Stereo requires that the subs are set up symmetrically in your room, ideally on either side of the listener

Those who believe in virtual bass arrays can place one on the right and one on the left?..

 

[Oddball]

Sorry, but one of my frank posts. You guys are splitting the hairs without having the solution. Bass management is quite difficult and what you are discussing is less than a very small part of it. There will be much more challenging decisions and adjustments to be made before you can resolve your issue.

One way to avoid it is to use room EQ that will cater to a different approach and possibly cater to both sides (Dirac ART ).

 

[thcdru2k]

I think its even worst than that. Conceptually ART is designed around a listening region in a bounded area. Basically rooms that behave like a room. 4 walls, well defined areas. Semi-open/fully open living rooms where the surrounds may be in the middle of the room with multiple connected areas, hallways, off-axis listening areas may not work to well or present a whole different challenge. Hard to tell ART hey I need you to optimize outside of your surround bubble. Not only is bass management difficult I think everyone is trying to basically solve different issues and trying to tell everyone else what they did to solve their issues when its not really anyone else's issue.

 

[Oddball]

I think its even worst than that. Conceptually ART is designed around a listening region in a bounded area. Basically rooms that behave like a room. 4 walls, well defined areas. Semi-open/fully open living rooms where the surrounds may be in the middle of the room with multiple connected areas, hallways, off-axis listening areas may not work to well or present a whole different challenge. Hard to tell ART hey I need you to optimize outside of your surround bubble. Not only is bass management difficult I think everyone is trying to basically solve different issues and trying to tell everyone else what they did to solve their issues when its not really anyone else's issue.

Not getting the point. Not aware of any solution that would optimize the whole area of irregular open floor plan "room" with adjacent areas. I happen to have ART in a "room" like that and it is doing a great job optimizing MLP and larger area. I might be a bit selfish so run a single MLP optimization. If someone appreciating the audio nuances happens to be in the room, I courteously allow them to use my spot.

When taking measurements with ART, like with any other room correction system, you can optimize for a narrow MLP position (one seat) or larger area including side and back seats. ART actually does a great job optimizing a larger listening area, but at the expense of not being so dead-on at MLP seat.

 

[Mort]

I might be a bit selfish so run a single MLP optimization.

This is the way.