Best bass in Earth! Bass that just smells right...

Hello tomic601, Jim,

     Thanks for the info, I agree with your high and low pass filter comments.
     There's also the typical about +3 db of bass room gain issue to deal with the use of subs.  I believe a steep low pass filter can help with this, too.

Later,
  Tim

Tim - well thought out and it works IF at 80 HZ you have a steep low pass filter. A steep high pass screws up time and phase And the bass higher order harmonics.
just about any Blue Note by Van Gelder will nicely illustrate this. Multi track rock n roll, not so much.For those who like free tools, download Vandertones. Besides, test tones tracks 13 and 14 are Acoustic bass scaling solos - those will be very helpful setting sub to main levels- Joe Harley recorded those at Oceanway... ya, that Joe
For those who want to see how much energy above 80 HZ there is, I will post up an RTA screenshot of track 14 in my Poverty Bay virtual system photo- it’s the last RTA photo.

enjoy the music, and the fun.

jim

millercarbon: " There is no stereo information at the lowest frequencies. Even if there is, there isn’t. I’m not gonna get into a technical spat over timing either. None of that matters. The simple fact is human beings cannot even hear low frequencies at less than one full cycle. Yes that is a fact. Yeah, science! So timing information or no timing information either way it doesn’t matter because you simply cannot hear it."

     As a user of the Audio Kinesis Debra 4-sub distributed bass array (DBA) system for over 5 years now in my fairly small 23'x14' room, I agree with everything millercarbon stated in his quote listed above.  
     The same debate over stereo vs mono deep bass was being debated over 6 years ago when I first began reading about the DBA concept and was considering buying the AK Debra or Swarm 4-sub complete DBA kit system.  I remember the price was $2,800 then and I didn't want to spend that much money on a bass solution, to pair with my then Magnepan 2.7QR main speakers, without being as certain as possible that it would work well and I was still a bit confused about the whole stereo vs mono deep bass issue. 
      My main concern was the possibility that the mono bass of the 4-sub DBA would smear, or otherwise degrade, the very realistic and detailed 3D stereo sound stage imaging I had achieved in my room and system at that time.  I also didn't want to wait for the cows to come home to find out whether or not stereo deep bass was worth pursuing. 
     
     I've come to the conclusion that 4-sub DBA systems, in combination with the main speakers, reproduce bass in a very natural and life-like manner.  When we listen to live music in a venue, we hear the fundamental sound of an under 80 Hz deep bass tone from an instrument that we're unable to localize (discern specifically where it is coming from) but we also hear the harmonics or overtone sounds, naturally produced and associated with the fundamental tone, that extend above 80 Hz and we are able to localize.  Our amazing brains are able to process these different sounds if heard within about 5 milliseconds of each other, determine they're related to each other and create the perception of specifically where the deep bass sound originated from.
     A 4-sub DBA system is creating the same audio conditions as live music, the only difference being that the 4 mono subs are reproducing the fundamental tones that are under 80 Hz that are omnidirectional and naturally heard as mono, anyway, and the main speakers are reproducing the harmonics or overtones that are above 80 Hz that are directional and naturally heard as stereo. 
      Add in our amazing brains to this mixture and we're perceiving all our reproduced music just as we perceive live music..  My opinion is that the above makes the whole debate over stereo vs mono deep bass moot.  The truth is we all perceive bass below about 80 Hz as mono and bass above about 80 Hz as stereo.       I
      Of course there's also the unfortunate reality for the promotion of stereo deep bass reproduction that, even if an individual owned an audio system capable of reproducing stereo deep bass down to 20 Hz with discrete left and right deep bass channels, there's an apparent complete lack of commercially available recorded music source material in any format that contains any stereo bass content below about 80-100 Hz.
     I've learned that it's been standard practice for at least the past 70 years for recording engineers to sum all recorded left and right channel bass below about 100 Hz to mono on their mixes for all recording formats. If anyone reading this knows of a single example of a music recording in any format containing stereo bass below about 100 Hz, please post it because it will be the first that I, and I believe most others, would be aware of.

     Given all the above facts, the approach that makes the most sense to me is treating our systems as 2 systems: 

1. a  Mono Deep Bass system for reproducing all frequencies below 80 Hz. 
     This serves as the solid foundation of the audio system, is operated in mono mode and these deep frequencies are best reproduced through the use of multiple, independently positioned subs with rated bass extension as close as possible to the audible bass frequency lower limit of 20 Hz. 
     The position of each sub in the room and in relation to the listening position are important. For best mono bass performance, a minimum of 2 subs is recommended but 4 subs have been scientifically proven to provide even better bass performance.  The optimum position of a pair of subs in a room is highly unlikely to be in a stereo or symmetrical configuration, with a sub located near each main speaker. If sophisticated and expensive measuring equipment is not available to determine the optimum position of each sub in the room, I've found the free 'sub crawl method' (google it) to be equally reliable. 
      Also, due to the omnidirectional radiation pattern and very long lengths of sub-80 Hz bass sound waves, the deep bass sound waves detected by our ears at the listening position are a combination of direct sound waves and reflected sound waves that have previously bounced off at least 1 room boundary (floor, ceiling or wall).  It's not uncommon for reflected deep bass sound waves to be the initial sound waves reaching the listening position.
     None of these deep bass sound waves have a left or right channel identifying sonic signature and all are perceived as mono.  Variations in pressure to determine direction, or perceiving deep bass sound waves as left and right channel, makes little sense sense in this context.  There is no stereo image created or perceived on bass frequencies below 80 Hz, it's all perceived as mono.

2. a Stereo Mid-range, Treble and Sound Stage Imaging system for reproducing all frequencies above 80 Hz.
     
     This serves as the detail center of the audio system, is operated in stereo mode and these higher frequencies are best reproduced through the use of a pair of independently positioned main speakers with rated bass extension that typically does not reach the audible bass frequency lower limit of 20 Hz.  
     The precise positioning of this pair of speakers in relation to the listening position improves mid-range and treble performance as well as optimizing the stereo sound stage imaging.  Our brains are also able to use the deep bass fundamental tone's harmonics or overtones frequencies, that are above 80 Hz and reproduced in stereo by the main speakers, and associate them with the deep bass fundamental frequencies that are below 80 Hz and reproduced in mono by the subs.  This process is what allows us to properly perceive the sound and location of the deep bass instruments within the overall stereo sound stage illusion.
     I believe this 2 system approach makes it initially simpler to understand how to create a very good quality overall home audio system and then how further improvements to either individual system will result in the overall audio system's performance improvement over time.

Tim

I read somewhere from an acoustical engineer that in "older recordings records then digitized" most of the deep bass was only in the left channel anyways??? Is this correct or does anyone know? If so all classic rock music (some of my favs) would be a boon to be in mono not a negative.

@millercarbon --

There is no stereo information at the lowest frequencies. Even if there is, there isn’t. I’m not gonna get into a technical spat over timing either. None of that matters. The simple fact is human beings cannot even hear low frequencies at less than one full cycle. Yes that is a fact. Yeah, science! So timing information or no timing information either way it doesn’t matter because you simply cannot hear it.

Let's indeed, to some extent, leave out technicalities - as you already proposed. And yet, you're all over it, right? I'll give you this: whether there is, or how frequently stereo information below, say, 100Hz is actually in the (digital) source material, is debatable. I doubt there's a comprehensive study on this, but I'd welcome more thorough insight on the matter - should it materialize. 

If stereo information is actually there down low in the source material, you're claiming it wouldn't matter because, as you write, we're not able to hear it. Ok. For stereo in general to matter, where we can aurally perceive it, it'd certainly nail the importance of placement re: timing. In regards to the lowest frequencies, however, what we hear may not be that important, and this could explain why some people fuzz about the importance of symmetrical placement of dual subs:

Stereo or not, I'd wager variations of pressurization in the lowest frequencies in regards to the distance and (possibly) direction of two bass sources, are perceivably felt. We may not be to tell exactly where they're coming from, but more importantly some of us can distinguish whether the pressurization is in unison as a combined output with the mains, i.e.: coming from equally distanced and directed sources (again, in relation to the mains) or not. The marker to me is for the integration with the mains to feel the most compelling, and to my experience this comes from placing the two subs symmetrically to the mains, preferable near them. The sonic image just falls into place here. I've tried close to endless combinations of placing my current subs non-symmetrically to my mains in my former listening room, and they never "clicked" the same way with the mains compared to the symmetrical solution. I speculated whether a diagonal placement of the subs in my current abode would make a worthwhile difference in regards to room mode cancellations, but so far I've chosen to trust my findings made earlier. 

This is not about stubbornly maintaining a position, but rather questioning a categorical approach presented by you that goes contrary to the experience made by some. You say it doesn't matter, but there are those of us who says that it does. Do you think telling us how things (presumably) work suddenly inverts our experience - why the urge to speak for all? 

Both the physics and the psychoacoustics of really low bass are so radically different than midrange and treble I am about ready to give up trying to explain. One in a hundred pays attention and thinks. The rest already have their closed minds made up.

Well, you certainly made up yours on this matter, supported by your beloved science. I can buy "paying attention" - indeed that's paramount when listening and evaluating. However, the thinking part comes up short when failing to take into account the "intel of listening" in forming an opinion that tries to dictate perceived impressions.

There is no stereo information at the lowest frequencies. Even if there is, there isn’t. I’m not gonna get into a technical spat over timing either. None of that matters. The simple fact is human beings cannot even hear low frequencies at less than one full cycle. Yes that is a fact. Yeah, science! So timing information or no timing information either way it doesn’t matter because you simply cannot hear it.

Both the physics and the psychoacoustics of really low bass are so radically different than midrange and treble I am about ready to give up trying to explain. One in a hundred pays attention and thinks. The rest already have their closed minds made up.

But wait! Miller! You are famous for saying your system has taut articulate 3D holographic bass! Liar liar pants on fire!

And that’s intellectual and tightly reasoned compared to the mindless repetition that is sure to come.

Whatever. Look. What people hear at low frequencies is volume. Period. Higher up we hear all kinds of detail. Down low its volume. Our brains and ears take the volume down low with the detail higher up and from that combination construct the 3D experience of stereo bass.

That’s the only explanation that fits all the observable facts. It explains why my 4 and 5 sub systems have exactly as much holographic 3D imaging when run mono as stereo. Exactly. The. Same.

So there is stereo, in the sense it can be heard. But there is not, in the sense its really mono.

@haywood310 --

From my experience so far.if you have two subs run them in stereo next to your mains. Basically creating "TRUE" full range speakers. No matter what your mains claim to be on the brochure. If you have more than two Mono is the way to go and aim them away from you like Duke says. Swarm Subs aka more than 3 can act as room treatments by cancelling nodes or adding room nodes to make you smile. Although I am going to test this theory in my room this week. Getting another AMP tomorrow to have 4 independent channels of amplification with separate X overs, phase, and volume control for each of the four 4 subs. I will run them both ways and see what I like best. Also side note 16 ohm with the subs can sound better than 4 ohms even though your getting more juice outta the Bass Amp at 4 ohms. Its past my IQ but it does change the sounds better sometime sometimes not.

Just my 2 cents.

Allgood!

Thanks for your reply and sharing your experience on the use of dual subs, and where and how to connect them. That's exactly how I'm running mine, closely flanking the mains and in stereo (see my profile). I did consider placing the subs diagonally, but for now the current configuration will remain. I just recently implemented a few acoustical tweaks and a subtle PEQ correction on the subs, and it made a worthwhile difference making the response down low flatter while having a positive influence through the midrange on up. It's amazing what minor tweaks can do, when you know where to put them into effect. 

phusis420 posts

From my experience so far.if you have two subs run them in stereo next to your mains. Basically creating "TRUE" full range speakers. No matter what your mains claim to be on the brochure. If you have more than two Mono is the way to go and aim them away from you like Duke says. Swarm Subs aka more than 3 can act as room treatments by cancelling nodes or adding room nodes to make you smile. Although I am going to test this theory in my room this week. Getting another AMP tomorrow to have 4 independent channels of amplification with separate X overs, phase, and volume control for each of the four 4 subs. I will run them both ways and see what I like best. Also side note 16 ohm with the subs can sound better than 4 ohms even though your getting more juice outta the Bass Amp at 4 ohms. Its past my IQ but it does change the sounds better sometime sometimes not.

Just my 2 cents.

Allgood!



@audiokinesis --

(@brotw posted: " As I understand it, an array of subs would be very effective at smoothing out the bass response of the room over a wider sweet spot. What about spatial cues from bass frequencies? ")

The good news is, you can have both.

My understanding is that true stereo below 80 Hz is actually quite rare, but if you want the ability to reproduce it, then (assuming four subs total) send the left channel signal to the two subs located towards the left-hand side of the room, and the right channel signal to the two subs located towards the right-hand side of the room.

Assuming there is stereo information below 80 Hz, rare it may be, and that one, if placement allowed, would like to take advantage of stereo information here, how would you approach connecting a diagonally positioned pair of subs (just 2, not 4) - like, one sub in the front left corner, and one in the rear right corner? Would you still hook them up in stereo being one sub is effectively placed to the left (front), and one is to the right (rear); or, would you rather connect them in mono?

To really set up your subs to their utmost ability without cancellation you need Mini-DSP. It may be fiddly at first but it is acclaimed as one of the best and least expensive solutions available.https://www.youtube.com/watch?v=E4OY0MhMKTc
https://www.minidsp.com/

Thanks Art for the info... Im thinking I was a different kind of Mechanical Engineer than your used to. And Im a former Marine so please grade this response on a curve. haha. 

Think HASS 3 to 5 axis mill. Master Cam and G code along with and a really big hammer and press... Im terrible with computers and new programs. Do you an old geezer Power user of your products that could come over in Phoenix and give some recommendations? Id pay him for his time. No substitute for wisdom and first hand experience.

lmk you can PM me if you dont his/her info out there.

As a side note..the Dayton Audio SA-1000 looks to be a rebadged Snell-SPA750.


I think I read somewhere a few years back that Bob Carver actually did the design work on the amp,  not sure if thats true though.

never heard this, it must make my stereo pair of 15" woofers seem like a feather in the holland tunnel.

mijostyn,

With the distributed array techniques with me - as millercarbon would say trying to ’wrap my head around’ how to do it, I too thought of the anthem bass management but I think that system is setup to work with only 2 subs?

Even if you used 2 splitters for the 2 bass pre outs (for a total of 4 subs) that are in the anthem that are in parallel which I think is mono anyway?

And not with 4 subs placed in optimal places in the room? It would probably work better with it off as you could work with each of the 4 individual subs in their own specific locations. As mono is fine with the distributed array technique. If the subs had maybe separate gain, delay, crossover, powered/active and or room size functions.

As I don’t have the 4 subs as yet, I do believe in the viability and high quality of bass sound it could produce for me in my place. It just makes sense.


audioman58 & haywood310

I think there is a misconception that everyone that buys a sub wants it for that ’Home Theater gut busting slam’. That couldn’t be farther from the truth. There are quite of few people that have purchased subs for a better and higher quality of bass reproduction of sound - period. Don’t get me wrong my PSA V1801’s could make my ears bleed. But gut busting decibels at ear bleeding levels ain’t what I’m looking for. And where does it say that the distributed array technique can’t be used for home theater?

I’ve always found it questionable when someone spends thousands of dollars on floor standing speakers and later realizes that the single 10" sub in them just doesn’t do it for them when it come to bass reproduction. Not only questionable on the buyers part but the manufacturer’s too. Hey, but we all live and learn.

My old CERWIN VEGA D-9s’
not boomy, tight, precise, best woofer I’ve ever heard.

yes, I still use them.
 They are the best rock speaker ever built.

 Bought new in 1986, and brought them home in my 1984 Cutlass supreme, one in trunk and one in backseat.
 Best rock speaker I’ve ever owned, I’ve owned. QUITE A LOT !

Would it eventually be better with four different subs while each could be expected to have a different frequency response in the room and together a smoother total freq resoponse?

Allgood, All you ever needed were 4 12" subs in very heavy and stiff sealed enclosures, two QSC commercial AB amps and bass management as found in the TACT room control units or those by Trinnov and I believe Anthem has the same capability or a dBx Drive Rack. A few measurements and you are in business. It helps if you have a good room but with four subs not quite as important. 

Is that your current setup in your avatar photo?

I bought a Dayton SW 1000 rack amp and its a great AMP for cheap. But I felt my 16 ohm Kinergetics were not a good fit all in Mono. Plus it has a thump when the AMP is turned off. Sure its 1 in 1000 defect and Parts Express is graciously taking it back. No volume control over the rear and front is driving me crazy. Im hoping stereo and fade (rear and front) volume will be the best possible. I Did just find a a Kinergetics SW 200v mono with a Compusound II circutry as well as an older BSC 200 stereo Sub AMP on Ebay both 100 bucks plus shipping and I won the bids so lil less than 300. The Mono SW 200 Amp is already here and sounds great just running my two fronts. And non adjustable X over at 100 HZ which makes me cringe but these Kinergetics SW 800's are really really good and sound great crossed over that high. This set up once I get the other stereo AMP should allow me Stereo up front and a volume control for the rear. Unless any experts here say try somethings else??? Next will be an used Aragon, Levinson, or Krell in stereo for the front and try to make the rest of em work. Im guessing if I get my stereo perfect then add the swarm I should be in good shape. 

Side note... super jealous of that guy with 4 SVS 16's and a Audio Engineered room!!! I wanna be him when I am reincarnated... haha or at least his dog so I get to listen and get treats!


"The mono-vs-stereo subwoofers issue is most likely to come up for a system like my Swarm, where all four subs are passive and can be driven by a single amplifier for mono bass, or by two amplifiers (at additional cost) for stereo bass. If you have two (or more) powered subs, imo you might as well connect them in stereo if that’s feasible.

My understanding that stereo bass is rare is largely based on a conversation with Earl Geddes wherein he described working as a consultant for Ford and the question arose of whether or not to provide stereo low bass for a high-end sound system. So he asked all of the engineers to bring in their CD’s. I don’t recall how many he analyzed, but he did not find a single one with stereo information below either 80 Hz or 100 Hz (my memory is foggy on the exact figure). I think there are audiophile recordings with true stereo bass, seems to me I read about some many years ago, but I didn’t make note of what they were. If anyone reading this knows of any recordings with true stereo south of 80 Hz, I’d be very interested in knowing about them.

Duke"

I played bass through a Sunn Sceptre with 4-12's (412) in the late '60's and early '70's and got a GREAT bass sound, so multiple small drivers can work quite well--at lease 4, anyway.  Options included one or 2 15-inch JBL D-140's.  The 412 was a bit "tighter" and the 115 and 215 cabs were a bit "deeper" in sound (Fender Precision bass).

We also built cabs for the Levinson HQD systems in the mid-'70's using Hartley 24" woofers.  LARGE cab, but pretty impressive bass, especially on good recordings. 

You can get wonderful bass (reproduction) from several types of transducers.  Choose the ones that sound like YOU want them to in YOUR room.

Cheers!

Kalali asked, "Duke, how do you handle the adjustment of phase at -90 degrees between the two (or four) passive subwoofers while using only one amplifier in the Swarm system? Does this approach require two or more amplifiers each with a separate phase control? " 

In a Swarm system, the 90 degrees apart adjustment calls for a second amplifier.

The amp that I use has a 0-180 degrees continuously-variable phase control. It’s the Dayton Audio SA-1000, available from Parts Express, in case anybody wants to "roll their own" passive multi-sub system.

Duke

Duke, how do you handle the adjustment of phase at -90 degrees between the two (or four) passive subwoofers while using only one amplifier in the Swarm system? Does this approach require two or more amplifiers each with a separate phase control? 

Decoupling bass frequency from mains allows for smoother room response using multiple subs, but I wonder how anchored in the soundstage 40-80Hz notes from stand up bass would sound

They would sound great.

I was sold on the feedback sub woofer design of Thrax when I heard it the first time. The design feeds the position of the cone to the DSP to achieve very accurate bass.  http://audio-union.com/audio-union/thrax-audio/basus/

@millercarbon --

When Duke says "My understanding is that true stereo below 80 Hz is actually quite rare" what he means is unicorn rare. Something people talk about but never quite manage to find. There is no stereo bass information down low. Even if there were we’d never hear it.

If that's what Duke truly means I don't see how his recommendation to connect my subs in stereo (in proposed diagonal setting) would be of any consequence. That is, his recommendation wouldn't be wrong as such, but why opt for stereo if it's rooted in the conviction of being moot to begin with? 

Even so, arguing in absolutes on stereo vs. mono bass doesn't come from you preemptively knowing about this field to the bottom of the matter, but rather your wanting to be right about it; pragmatically I'm sure you speak for many, but what you're doing with it is just being overly reductive.

Brotw wrote: " Seriously, I’d have to play with crossover frequencies for best integration. "

Don’t forget that the phase control on the subs can help with integration. Sometimes overlapping the mains a bit + putting the subs somewhat out-of-phase with the mains gives the best results.

"...thankfully spatial cues are largely provided by the mains."

The spatial aspects are complicated. In a home listening room, there is in effect a competition between the spatial cues on the recording and the contradictory cues of the listening room. At BEST, we have a poverty of recording venue cues - nothing remotely approaching the veritable plethora of cues at a live performance. The magnificent ear/brain system is able to reconstruct a reasonable approximation of the recording venue (whether real or engineered) if cues consistent with the recording venue effectively dominate over the listening room’s signature. So regarding cues consistent with the recording venue, arguably every little bit helps.

The phase quadrature (90 degrees apart) setting with subs placed wide to the left and right of the listening generally contributes cues which support the perception of being in a large acoustic space, which can help tip our perception towards the venue on the recording, or a reasonable approximation thereof, and away from the distracting awareness that we’re really just sitting in a small room pretending.

Duke

I think there are audiophile recordings with true stereo bass, seems to me I read about some many years ago, but I didn’t make note of what they were. If anyone reading this knows of any recordings with true stereo south of 80 Hz, I’d be very interested in knowing about them.

I think the question really is going to be, how does this get recorded and mixed? I don't think recording engineers are low passing all tracks and replacing them as a mono element, unlike perhaps movie sound tracks, where the LFE channel can be used for greater dynamic range.

More likely the percussion all ends mixed together and put in one place.

I mean consider a case of a double bass off to the right, and a piano to the left. I've never heard of any recording engineer taking the bass alone and mixing it to mono.  Would be very interesting to hear from actual recording engineers.

Having said this, properly integrated, where a sub is physically located should not be discernible.

Duke, I'll go along with the overtones providing soundstage placement through the mains. As far as sub placement, stereo subs could be positioned on the L/R walls rather than the opposite corners as you alluded to in your earlier post, but thankfully spatial cues are largely provided by the mains. Anywhere you want it, that's the way you need it (as long as REW says so)

Seriously, I'd have to play with crossover frequencies for best integration. The other issue is high level or low level inputs for those of us without bass management. I see reasoning for both.

Still need to get subs, just wonder how many.

I don’t like to brag but you people would not believe the bass that’s right there on the CD. But you just can’t hear it, that’s all. It’s like trying to excavate for the jewels of some Egyptian King. But, alas, the CD machines have never been able to excavate the CDs properly. Not even close. But in the DC area there is one place you can go to hear it. No, not my place.

When Duke says "My understanding is that true stereo below 80 Hz is actually quite rare" what he means is unicorn rare. Something people talk about but never quite manage to find. There is no stereo bass information down low. Even if there were we’d never hear it.

Mine are actually hooked up L/R now. Actually three on the left get the left channel, the right channel goes to the two on the right. But I tried it lots of ways, including all mono, and the one thing you will never hear is any difference between stereo and mono. Between 4 ohm and 16 ohm, for sure. Different positions, yes but not to the same extent. Phase? Even less so.

Stereo bass is definitely a thing. I could play you one recording after another, and guarantee you will be freaking amazed at how much character, definition, and 3D localization there is to the bass. It does whatever it needs to do, from pin-point where the drum was hit to all enveloping cocoon of man cave magic. Whatever it takes, its there. But all that sense of where it is, is just as good whether subs are wired stereo, or mono.

@brotw posted: "Do 4+ instead of dual subs shine best in monitor/stat/maggie systems with subs crossed at ~80 HZ?"

I think that’s a fair statement. But I have customers crossing over their Swarms at the minimum 30 Hz setting and finding them to be a worthwhile improvement over one or two subs.

@brotw again: "Decoupling bass frequency from mains allows for smoother room response using multiple subs, but I wonder how anchored in the soundstage 40-80Hz notes from stand up bass would sound."

I use a 4th order lowpass filter so that any subs far away from the mains don’t pass upper bass/lower midrange energy loud enough to give away their locations. To the best of my knowledge this has worked well for crossover frequencies up to 80 Hz. I don’t think there would be any problem with upright bass, especially since the ear will tend to localize the notes based on the overtones rather than the fundamentals.

@phusis posted: " Assuming there is stereo information below 80 Hz, rare it may be, and that one, if placement allowed, would like to take advantage of stereo information here, how would you approach connecting a diagonally positioned pair of subs (just 2, not 4) - like, one sub in the front left corner, and one in the rear right corner? "

I’d send the left channel signal to the left front corner sub, and the right channel signal to the right rear corner sub.

The mono-vs-stereo subwoofers issue is most likely to come up for a system like my Swarm, where all four subs are passive and can be driven by a single amplifier for mono bass, or by two amplifiers (at additional cost) for stereo bass. If you have two (or more) powered subs, imo you might as well connect them in stereo if that’s feasible. 

My understanding that stereo bass is rare is largely based on a conversation with Earl Geddes wherein he described working as a consultant for Ford and the question arose of whether or not to provide stereo low bass for a high-end sound system. So he asked all of the engineers to bring in their CD’s. I don’t recall how many he analyzed, but he did not find a single one with stereo information below either 80 Hz or 100 Hz (my memory is foggy on the exact figure). I think there are audiophile recordings with true stereo bass, seems to me I read about some many years ago, but I didn’t make note of what they were. If anyone reading this knows of any recordings with true stereo south of 80 Hz, I’d be very interested in knowing about them.

Duke

I guess noone has never heard the perfect bass.

@audiokinesis --

(@brotw posted: " As I understand it, an array of subs would be very effective at smoothing out the bass response of the room over a wider sweet spot. What about spatial cues from bass frequencies? ")

The good news is, you can have both.

My understanding is that true stereo below 80 Hz is actually quite rare, but if you want the ability to reproduce it, then (assuming four subs total) send the left channel signal to the two subs located towards the left-hand side of the room, and the right channel signal to the two subs located towards the right-hand side of the room. 

Assuming there is stereo information below 80 Hz, rare it may be, and that one, if placement allowed, would like to take advantage of stereo information here, how would you approach connecting a diagonally positioned pair of subs (just 2, not 4) - like, one sub in the front left corner, and one in the rear right corner? Would you still hook them up in stereo being one sub is effectively placed to the left (front), and one is to the right (rear); or, would you rather connect them in mono?

I’ve got a 20’x16’ room also, not fully sealed, opens to a stair case at the back, but the room modes that come with this dimension are anything but ideal. Appreciate the tips Haywood and believe you are on the right path.


@audiorusty
That sounds like a good technique for pairing smooth bass with your bookshelfs. I might try that! My Tekton DIs reach down to 30 HZ on REW, and have a flat response down to 20 Hz after Dirac Live calibration. Bass is authoritative down to ~ 40 or 50 Hz using a 48W SET LM508IA integrated. Just because Dirac says I’m getting it, doesn’t mean it’s punchy and as tight as I’d like.

@audiokinesis

That 90 deg. phase idea is interesting. Assuming the use of rule of thirds for speaker and LP placement which I found to be not far from ideal, optimization of placement for a pair of subs on the left side wall, and a pair on the right might work (only 4 variables). Multiple optimization sub placement solutions for different crossover frequencies might further results.

Sub crossover frequency suggestions always seem to be around 40-50 Hz for best integration results with mains that dig deep (no bass management). I’m thinking at those frequencies there are few room modes you are trying to smooth out with subplacement. Do 4+ instead of dual subs shine best in monitor/stat/maggie systems with subs crossed at ~80 HZ?

Decoupling bass frequency from mains allows for smoother room response using multiple subs, but I wonder how anchored in the soundstage 40-80Hz notes from stand up bass would sound.

@brotw 

In order to reproduce spatial cues at bass frequencies, don't you need dual subs sitting next to the mains?

I have a pair of bookshelf speakers that I integrated with a pair of subs. I am crossing over much higher than 80hz to protect the 5 1/2" driver in the bookshelfs  from over excursion during loud playback so my set up is as you described with the subs inline with the mains. I recently added a third sub and due to the extremely small room I really didn't have any placement options except right behind the listening position on the left side of the room firing into the room at a 90 degree angle to the front speakers. The third sub is crossed over at 80hz. The bass in the room became much smoother and more impactful and sounds like it is coming right at me from the front of the room. I can reach back while sitting in the listening position and touch the surround of the sub behind me and feel it moving but all the sound I am hearing is in front of me. It's really kind of wild how it all comes together.

I send the left channel to the front left sub, the right channel to the right front sub and both the left and right channels to the third sub.

You guys are single aren’t you?

Sub madness...they're swarming! I get it, but I also get great bass from a couple of RELs, so hey...at least I am part of the "multiple sub" subgroup.

I'm about to pull the plug on a pair of sealed subs from the same maker of my main speakers, who seemed to have done a lot of work to make them integrate seamlessly. I'm looking to enhance the frequency range between 50-20 Hz, planning to connect them with high level input (speaker level) to get the same bass signature of the amp.
Thanks to posts by you and other people who swear who important subs are to complete the sound of a stereo system!! Hopefully i will find out soon for myself ))

@brotw posted: " As I understand it, an array of subs would be very effective at smoothing out the bass response of the room over a wider sweet spot. What about spatial cues from bass frequencies? "

The good news is, you can have both.

My understanding is that true stereo below 80 Hz is actually quite rare, but if you want the ability to reproduce it, then (assuming four subs total) send the left channel signal to the two subs located towards the left-hand side of the room, and the right channel signal to the two subs located towards the right-hand side of the room.

If you’d like to synthesize the sort of immersive ambience we might get from true stereo bass, try this: Set the two subs on the left-hand side of the room both 90 degrees apart in phase from the two subs on the right-hand side of the room. So for instance if the two left-hand subs have the phase control set at 30 degrees, the two right-hand subs would have the phase control set at 120 degrees. Credit to David Griesinger (inventor of the Lexicon processor) for this idea; his original suggestion was to use two subs, located along the side walls to the left and right of the listening area. That 90 degrees phase difference isn’t necessarily carved in stone either - you can go beyond 90 degrees, at the expense of increased cancellation at the very bottom end (which in some cases may be desirable).

Duke
(disclaimer, in case the connection isn’t obvious: I make the Swarm)

As I understand it, an array of subs would be very effective at smoothing out the bass response of the room over a wider sweet spot. What about spatial cues from bass frequencies? What frequency does bass directionality kick in, 50hz? In order to reproduce spatial cues at bass frequencies, don't you need dual subs sitting next to the mains? Any more subs or in any other location other then dual subs next to the mains would destroy that I'm thinking. Perhaps the smoother, more tonally accurate response from 4 or more subs is the better route.

Just build a bomb shelter (no really, we’ll probably need one in the immediate future) but set a room up with as much soundproofing/dampening and then start dropping subs IMO. Think about how dampening improves sound in a car. 

My friend has 4-SVS ultra 16inch subs. his den on movies or music it is devastating .his living room  was designed for home theatre the
literal punch in the stomach ,the pressure wave literally attacks the senses and the subsonic effect from a giant Hammond pipe organ rumbles your guts and the room at under 20 hz and then Japanese 8 ft drums is like the drums heads are in the room .the 1812 overture was a liberal Giant cannon Explosion which was disorienting at over 105 DB hitting you from 360 degrees in the dark was equal to a artillery shell in the service.4x16 inch drivers and 1,000s of Watts on hand .i have yet to see this equaled Anywhere.

I finally find myself with 26 10 inch woofers (only using 20 at the moment) from four Kinergetics sw 800's in a small 20 x 16 room. 4 towers with 5 10
inch Seas each and 2 of the smaller subs with 3 10 inch woofers each

I dunno, maybe, 1-2 subs, and bass traps with appropriate EQ  is sounding pretty good right about now. :)

Go Church Go!!!

Why I prefer the giant bass horn approach since they load a room fully and are fairly immune to placement and other room issues. You just get bass pressure.

Bass that smells who would want that in they're listening room?

Mmmmm I love the smell of
bass in the morning. Smells like Trepaneringsritualen

Well said Haywood . I am running 6 subs in my room  using a DSPeaker anti mode 2.0 as a sub preamp, crossover and DSP . My speakers are sealed cabinet 2 way monitors . Rock music is just great in my room . 
Distributed bass must be heard by all the naysayers to convince them .
As they say ignorance is bliss 

I remember the Kinergetics from years ago. If memory serves they were exceptional and the best I had ever heard back then.