Distributed Bass Array configuration

he's not just well informed, but one of the real gentlemen in our field.

Duke is one of those people that I regard as a model human- a gentleman, well versed and an honor to know as a friend.

@atmasphere +1. Never met Duke but that rings true from what I have seen over the years here.  I have learned a lot from him here over the years.   You too!

What ruled the Amethyst out for me was that it has a fan

My XO has a fan also. (XTA DP448) I disabled the fan but left the top cover off so it would cool properly. All with XTA's blessing.

     The following quote was copied from a Stereo Times interview with Duke Lejeune that took place many years ago, There was no date listed on the article that I could find.  So, I'm not certain of the exact date but I believe it was published around the year 2000 give or take a few years.
    I thought the entire interview might be of interest to members and this is a link to the complete interview:

 http://www.stereotimes.com/comm081710.shtml

     
    The interview begins with a fairly lengthy portion about his regular speaker designs.  The copied portion below is a portion near the end of the interview, which I thought was more directly relevant to this thread since it is the portion at which "LB", Stereo Times interviewer Larry Borden, first asks Duke, "DL", about his "SWARM" 4-sub distributed bass array system:

"LB: Let’s turn now to bass. What is “SWARM,” and how does it work?
DL: The concept behind the Swarm arises from a brief conversation with Earl Geddes, as I was driving him to the airport after CES in 2006. I had been trying for years to come up with a subwoofer system that would match up well with Magneplanars and Quads, trying various enclosure types in a quest for very good “pitch definition” in the bass region, along with good impact (good planars excel at the former but not the latter,). Anyway, Earl mentioned that scattering multiple subs asymmetrically around the room resulted in a net smoothing of the in-room bass, as each sub would interact with the room differently so that the sum would be smoother than any one alone. The lightbulb went off in my head, and I asked him for permission to use the idea. He said yes. By the time we got to the airport, I was already designing the Swarm in my head. Let me digress for a minute into acoustics and psychoacoustics. The ear/brain system tends to smooth out peaks and dips that are fairly close to one another, but if they are more than 1/3 octave or so apart then the peaks and dips are usually audible. Now we get room-induced peaks and dips all up and down the spectrum, but only in the bass region are they typically far enough apart (due to the wavelengths involved) that the ear cannot smooth them out. So in the bass region the problem is not too many peaks and dips – the problem is that they are too few and far between! Another factor is that it takes the ear a fair amount of time to hear bass frequencies. The ear cannot even detect the presence of bass energy from less than one full cycle, and it takes several cycles to detect the pitch. So considering the wavelengths and room dimensions, by the time we can hear bass tones the room’s effect is in full swing. Perceptually, in our home listening rooms there is no such thing as “direct sound” in the bass region; by the time we even begin to hear it, it’s all reverberant sound.
The Swarm consists of four fairly small subs and a single kilowatt shelf-mounted external amplifier. The subs are “voiced” to have a gentle rolloff over most of the bass region that is the approximate inverse of anticipated room gain (the vented version comes closer to this ideal than the low-Q sealed version does). The amplifier has a steep 24 dB per octave lowpass filter so that the subs can be scattered without betraying their locations by leaking lower midrange energy, along with a single band of parametric EQ in case the scattering alone doesn’t do the trick. To the best of my knowledge, none of my customers are using the parametric EQ because the in-room bass is sufficiently smoothed as it is. Not only does the Swarm result in a smoothing of the in-room peaks and dips, but the peaks and dips that remain are more numerous and closer together, so that the ear’s smoothing mechanism can be effective. Now at first glance it might seem that multiple bass sources with multiple arrival times results in loss of impact and/or mud, but that is not the case in practice. As explained above, we cannot hear the bass wavefront before the room has its say. The ear responds primarily to frequency response (rather than to time-domain behavior) in the bass region, so when we smooth the frequency response we are solving the biggest problem. Because the low fundamentals and first few overtones are present in proper proportion, the pitch definition is very good. The argument for a single large equalized sub can of course be made, and there are some exceptional examples on the market, but equalization is a local rather than a global solution. In other words, the room-induced peak-and-dip pattern varies so much from one location to another within a room that fixing the frequency response at one location via equalization will almost inevitably make it worse elsewhere. In contrast, the multi-sub approach smoothes the bass throughout the room (decreases the spatial variance), ironically making equalization (if needed) even more effective."

     I thought his statement, "So considering the wavelengths and room dimensions, by the time we can hear bass tones the room’s effect is in full swing. Perceptually, in our home listening rooms there is no such thing as “direct sound” in the bass region; by the time we even begin to hear it, it’s all reverberant sound.", was especially relevant to this thread discussion.       He's basically pointing out that the very long and omnidirectional bass sound waves behave very differently in  domestic sized rooms than the much shorter and highly directional midrange and treble soundwaves.           Which means that sound wave time coherence, the timing of sound waves actually reaching a listener's ears, is very important, necessary and doable for the shorter midrange and treble frequency sound waves for good stereo imaging.  But sound wave time coherence is not very important, doable or even necessary for the much longer bass frequency sound waves since there is no such thing as "direct sound" in the bass region, it's all reverberant, or reflected, sound.  The fact that humans are poor at locating the source of sounds below 80 Hz and progressively better at locating the source of sounds above about 80 Hz, the fact that we require the detection of a long and full cycle bass sound wave to even perceive bass sound present in the room and several full cycle bass sound waves in succession to perceive pitch, also distinguishes the differences in bass versus mid/treble sound tone perceptions in our rooms.  
     Another interesting fact about bass sounds is that, perceptually, we're much better and more naturally able to perceive them outside or in a very large concert hall because the very long, full cycle bass sound waves, due to the much larger space, have  the capability to arrive at our ears as "direct sound" rather than arrive as reverberant sound that has reflected off one or more room boundaries on its path.

Just some food for thought,
               Tim

That is a great quote and relevant Tim, and thanks for saving me the time of reading the whole interview. Your last comment is one of the clues that helped convince me DBA was the way to go.   
The only times we experience truly low bass in normal life is in very large to wide open spaces. For me it was always one of the coolest parts of going to a rock concert, that vast space feeling of bottomless bass. This was always missing, particularly in orchestral works, because even if it is on the recording the system simply cannot reproduce it at home. Even if the system response measurements look good still there is always the room that ruins this.   

I'm sure you know where I'm going with this. One of the more surprising things with a DBA is the enhanced feeling of envelopment. People have commented on it with my system. It is very deceptive. First, because no sound whatsoever appears to be coming from the subs at all. But also because the low bass that triggers this feeling isn't even heard or sensed as bass at all. It has no pitch, nor location. It has no attack or slam, no harmonic, no tone at all. Yet somehow it creates this ineffable feeling of being in a huge space.  

Nothing else does this, at least not to this extent, and I have heard some pretty awesome gear in some damn fine rooms. Yours as I recall are one per corner. Another one has this plus one way up high near the ceiling. Mine are along 3 of the 4 walls. It seems to work well almost regardless of how the subs are laid out.

Please correct me if any of my comments here are incorrect as I don't claim to have any expertise. I do believe you are misinterpreting the  "term" - "stereo subwoofers". It is a "term" not a sonic phenomena or an implementation in any recording process . I do believe it was originally  meant as the description of using 2 subs on receiver/pre amp as 2 separate channels so not to not to be confused with 2 sub outputs running parallel. Although this is a 2 channel discussion listening subject  I do believe the whole concept began with surround sound and then was deemed profitable for 2 channel listening. So, when a surround sound mix is configured for a movie the "LFE" channel is single and mono ( as is every channel / speaker ), it does not have a left sub mix and a right sub mix, much less a 4 sub mix, it is a single signal. Then the receiver through it's processor separates it to a left channel and a right channel so the mic calibration processing then allows for different volume levels to be "matched" at the listener position. Now recent implementations of Audyssey and definitely Dirac LIve may incorporate separate phase shift and delay but it all comes from a single mono signal being manipulated to create a "means to an end".
Again correct me but isn't "stereo" in itself just taking a recording from multiple "mono" microphones and then an engineer manipulating all the separate mic channels into a "stereo mix" in an effort to create a "perceivable" soundstage again as a means to an end ? I think we should use the term multiple.
I listen to Paul McGowen on Youtube ( maybe the meaning of stereo subs is a good question to send in ) and consider him quite informative but don't take all he says as undeniable truth. Actually, I believe he has mentioned that the owner of Audioquest is a friend of his and I heard that guy the other day on YouTube say that power regenerators are useless ( and a great amount of Paul's expertise and companies monetary value is based on that very component ) so I guess even his friend and also an "expert" doesn't agree with him. I might mention that his company is often criticized as not legit in the premises that their products are based on . So who are the experts? 
But let me conclude in complete agreeance that we can't discern the location of the lowest frequencies, it's just a fact. Our ears/brain don't work that way for a reason. In real world circumstances there is no practical use for "hearing" those frequencies. One main component of hearing and discerning placement is to realize where danger may be coming from and if your in danger from something creating sub harmonic frequencies it's probably an earthquake and you ain't getting away from that.

My B&W older 803's, as well as my stacked DM24's sat on top of my stereo subs.  I measured the woofers on all speakers and phase aligned them.  I know that it is taught that sub-wooferage is non-directional, but tell that to my ex-laundry room bass trap, electronics room when the door is left open.

Any Sub Woofer set @ 80 HZ Crossover will interact with every Good Hi Fi Speaker's Bass Output.  This should be avoided.

Setting @ 60 Hz or so should minimize interference & blend in better.

With Sub Bass, a Crossover of 40 Hz or so would be appropriate.

1Hz XO resolution on subs and mains is nice.
Sub and mains may not necessarily crossover at the same frequency and more than probably at different slopes.

I often imagine that DBA is a lot like what happened in a mastering lab in the LP days: After listening to glorious 2 channel bottom end in the studio, it got sucked down to mono below 40Hz. And these guys recommend 80Hz w no XO on the mains. Surely you jest?

soundspectacular:" Please correct me if any of my comments here are incorrect as I don't claim to have any expertise. I do believe you are misinterpreting the "term" - "stereo subwoofers". It is a "term" not a sonic phenomena or an implementation in any recording process."

Hello soundspectacular,
 
     You are correct, "stereo subwoofers" is just a term, perhaps only used on this audio forum, that does not represent an actual phenomena or an implementation in any recording process. 
      I consider stereo subs a misnomer since I don't believe stereo bass even exists below about 80 Hz, iwe all perceive it as mono.  But others on this forum believe stereo bass below 80 Hz does exist. 
     The whole stereo bass subject on this forum, unfortunately, only gets more complex and polarized from there, as well as too involved to easily summarize.

Hope this helped,
Tim
     

A lot of the challenge is that while there is no stereo bass in the bottom octave or two, it does sound as if it is stereo. The drum whacks in Bird on a Wire, each one has a definite location. The hall ambience and cannon on Tchaikovsky 1812 are all incredibly precise. When people think of mono they think of Beatle's and other mono records where the sound all seems to be coming from a sphere in between the speakers. That is NOT what we are talking about! This bass does not sound as if it is mono. Not at all.  

However, rest assured, it most certainly IS mono! Anyone harboring any doubt whatsoever is welcome to come and hear, I am happy to demo, and you will hear absolutely zero difference when my DBA is run mono vs stereo. Zero. Nada. Zip. None. Because it is all mono! 

This actually even makes sense, because when you think about it, how else could it be? The wavelength of these low frequencies are so long, that in order to be picked up as stereo the microphones would have to be located a hundred feet or more apart. Even then, our hearing simply is not sensitive to timing at this degree of precision at this low a frequency. We don't even hear less than a full wave! Don't even hear it! 

This is where I think a lot of this comes from. Everyone is familiar with midrange and treble. Everyone knows the importance of phase, timing, etc. This is all goes right out the window with low bass.  

Also by the way with ultra-sonics. Super-tweeters, 40kHz, 60kHz, we cannot even hear. Yet they affect the sound in such a big way it changes our perception of even low bass!  

The mind is a strange and endlessly fascinating thing. Hearing is not just mechanical. We like to use a microphone as a metaphor for how we hear. But that is not all there is to it. The phenomenon of hearing is far more complex. The mind plays a vital role. Try and get your mind around it. 

One thing to keep in mind: if you are using a sub (or four) with---I would certainly hope ;-) ---a low-pass filtered signal as its/their source, well, what is the slope of that filter? If only 6dB/octave (1st-order, as with the Vandersteen subs), that sub reproducing a, say, 80Hz signal, will be reproducing 160Hz (an octave higher) at only 12dB down. Who thinks a 160Hz wave cannot be located in space? How about 320hZ (24dB down)? Naturally a higher-order filter will change those figures.

If you run your sub(s) in mono, that mono output will extend further up in frequency that the frequency at which the x/o is set, the degree to which is determined by the slope of the filter. It is for that reason that some prefer employing higher-order filters (both high-pass and low) to integrate speakers and subs.

Doesn't surprise me at all 60ish khz effects bass perception...at that level, it becomes a 'physical' thing that likely vibrates your body hair...:)
Since you exist daily in an atmosphere soup, the reproduction of those fq adds to the 'reality' of the program....the suspension of disbelief...

I'll agree that L/R bass exists until the 'mono-ization' occurs, and it's all one motion due to wavelengths.  I like the concept of SWARM; smaller drivers quick enough to follow an amt...or a walsh. ;)

The thought of 'off the floor' placement in a smaller space (or a problematic one) has appeal...esp. looking forward to a new and improved place to hit 'reset' on my 'equipment'...*S*

(No recommendations, please. I agree with your selections; mine would likely bore or abhor but please me Enough.)

No, this is not occuring over this weekend.  I have important sloth to indulge in....plenty of time to run simulations.. *S*

-26db....*damn*  If fans bug you, your heartbeat and breathing are next..
Just teasing...don't stop. *g*

Happy 4 to all, play loud enough, J

Based on my experiences running a sound system, years as a bass phreak and a lifetime's work on my domestic rig, i can state with certainty that the ultimate bass is achieved by realising that bass is a part of the music, and should emanate from the same location, travelling in the same direction.

Sound is a pressure wave, and humans are capable of discerning the source of frequencies well below 20hz, let alone 80.
 Place one powerful subwoofer, crossed over below 40hz asymmetrically in a decent sized room and you will clearly, undeniably feel a difference in pressure coming from the side of the room with the sub.

I have enormous respect for the dba as a means to achieve excellent bass operating within parameters like cost , space and waf. 
But the ultimate, and most natural-sounding bass will be achieved from using main speakers with sub 20hz output, and stereo bass stacks sited alongside your main speakers, and firing in the same direction.( I go with a span's width between sub and main speaker.)
Furthermore subs need to be outside the main speakers if you plan on listening from the centre, and for most genres of music i bring the subs in at 40hz. Some dub reggae or deep house tracks get 54hz, but this can sound too thick with other tunes even of the same genre.

 In a nutshell, you have done all of the hard work deciding the best place to put your main speakers. In an ideal world, place your subs next to them. In a compromised world use the distributed bass array, and experience the enjoyable but artificial three dimensional effect described elsewhere.

In terms of using stereo or mono bass, i generally continue to fall into the same trap of imagining that bass is part of the music and should be treated the same as the main signal. By the time you are adding four or more subs you will have output to spare so there's no advantage to quadrupling a mono signal. However i am sympathetic to using mono bass to cope with imbalances caused by triggering room nodes.

I did try the Trinnov pre amp, but the Wavac pt-t1 tanned it's behind.
If your system is already correctly time aligned in analogue by having each drive unit the same distance from the listening position, there is nothing to be gained from the Trinnov's digital time correction. The dealer was crestfallen, he could clearly hear the same thing i did.

All that was left was the character of the pre amp, and my preference for a valve pre amp remained intact. Fortified, even.

< 20 - 60 hz is considered SUB BASS. It is MONO, I don't care what you do to it. BUT if there is a left and right SUB bass signal from the source that is replaying via the MIXED recording, you can't just use the left or right signal and call it good. 

I've read here on AG countless times "it makes no difference because its MONO", use either the left or the right output. NO!

You have to use BOTH LEFT and RIGHT signals to play the WHOLE bass track...

Second. BASS is directional PERIOD.. 60 - 80 hz is transitional from SUB to BASS. BASS is 80-250 hz. 

The problem is the decay rate of ALL the lower frequency waves 80 < loading the room and BOOMING.

I went to GRs OB servo system.. FIXED that problem, right NOW! BOTH sided of the cone are in the room. How simple is that? The only place and WAY OB works for ME.
It has a step baffle and a pretty well programmed firmware chip.. Rythmik plate amps.

The other problem is overshoot from 80-250 hz (where ALL the SLAM is).

THAT is where a lot of systems get sloppy from MB to MIDS, they get muddy and OVER-exaggerated low mids.. or bloated? I can't stand when the congas SUCK. or Cher's voice.. :-) A baritone girl or a Contralto (to be correct) sound bad.. 

I direct couple the MB columns to serious class d 12k pro amps.. and use an active full blown DSP XO. It Fixed the overshoot problem for the first time without a (SLOW A$$) VERY EXPENSIVE accelerometer set up.. 1/10 the cost..

There is a difference in SUBs and BASS BUT I keep seeing the TWO used as if they were the same thing.. I use two different drivers for TWO different things.. More floor space but a much bigger smile. :-)

    bdp24,
      The 4-sub Audio Kinesis Swarm and Debra DBA systems utilize a  Kilowatt class shelf-mount class AB amp/control unit with a 4th order variable lowpass filter that rolls off the bass at 3 dB per octave from 100 Hz down to 20.  
     The 4 sub modules have a gentle roll-off across their passband that is the approximate inverse of typical room gain from boundary reinforcement. Typical room gain from placement near a wall is 3 dB per octave below 100 Hz, and so the Swarm modules roll off at about

3 dB per octave from 100 Hz down to 20 Hz.  Here's a link to the system's description and specs: 

 http://www.audiokinesis.com/the-swarm-subwoofer-system-1.html

     When utilizing a 4-sub DBA in mono mode, I think it's important for everyone to understand that one is still able to perceive a deep and wide sound stage illusion in full stereo over the entire, standard and audible 20 Hz-20KHz frequency spectrum.   In other words, one is able to perceive stereo deep bass below 80 Hz and localize deep bass instruments in the stereo sound stage illusion.  

     I don't believe this bass perception, however, can accurately be classified as "stereo subwoofers" or "stereo deep bass" since the bass below about 80 Hz is technically being played back in mono.  In all the music source material I possess, the bass below about 80 Hz is also summed to mono during the recording process.

     My theory, about how this mono bass is perceived as stereo bass , is that bass sounds below 80 Hz have harmonics, or overtones, that reach beyond 80 Hz which are able to be localized.  These harmonics or overtones are recorded and played back in stereo through the l+r main stereo speakers. Our brains are then capable of associating these over 80 Hz harmonics/overtones, coming from the main l+r speakers in stereo, with the under 80 Hz fundamental tones, coming from the 4 subs in mono, and creating an overall perception of stereo bass that specifically details where in the 3 dimensional stereo sound stage the sound is coming from in a very natural and realistic manner.  

     My opinion is that this type of stereo deep bass perception is unique and deserves its own name or description, other than "stereo subwoofers" or "stereo deep bass".  I find a fairly low crossover frequency between 40-50 Hz performs best in my room and system for both music and HT.  Even though I know the bass is mono, I definitely perceive the music as high quality, very natural, very realistic and in full range stereo.

Tim

Tim yes correct. If I walk into a room with somebody bowing the low string on a cello, which is 41Hz, I can tell where it is. If the first 2 octaves can’t be localised then how is this possible?

It’s the harmonic overtones providing the spatial clues and the preservation of these overtones is vitally important to the entire spectrum.

It would not be possible to locate a signal generator producing the  same 41Hz .  as a sine wave.

noble101

There is no such thing as stereo bass below 80 Hz since it's a fact that humans cannot determine the originating location of any sound deeper than approximately 80 Hz.

That wasn't a fact back when you argued this under your old username (noble100). Remember? Tthat led to such vile, profane arguments from you that you were banned from the group. Now you're back with same same pronouncement.

If anyone thinks they're able to distinguish the specific originating location of bass below 80 Hz, I'd suggest testing this for themselves ...

Some of us have actually tested this, using both commercial and original recordings. You might want to try it for yourself sometime.

... Timing and arrival time of deep bass sound waves at an individuals ears are, therefore, also not anything to be overly concerned with since a 20 Hz bass tone sound wave is about 56 feet long, which likely exceeds the dimensions of at least the length or width of most domestic rooms ...

Non-sequitur.

The truth is ... we're still not able to determine specifically where these bass sound originated from if they're below about 80 Hz.

That's not quite true. Nor is that the standard for proving whether there is such a thing as stereo bass. Because phase matters, stereo bass can sound different than mono bass. It's not solely about localizing LF.

... Recording engineers have been routinely summing left and right bass under about 80 Hz as mono, and sometimes even higher, as a standard practice for over 4 decades.

It's not a universal practice and it originated as much for the convenience of the end user - to ensure trouble-free playback on cheap turntables - as it did to make things easier for the mastering engineer.

Because these recording engineers have known the truth about the myth of stereo deep bass for about the last 100 years, ever since scientists first discovered and formally established this fact through the scientific method. Don't believe me?

You do not know what you are talking about. First, we didn't have stereo 100 years ago. We didn't have the LP, either. Or tape. And I can prove to you through simple measurement that there is such a thing as "stereo bass." That is, I can show you that it is possible for bass recorded and played back in stereo to sound different from the same recording with bass summed to mono. 

@noble100 @noble101 you might want to get your head out of Secrets of Home Theater and your tattered copies of Stereo Review and stop fabricating imaginary scientific studies. You might also want to review the references about this that I gave you before you were banned from the forum, because you are just making yourself look silly here. After all, if those scientific studies you claim were conducted 100 years ago actually existed, the researchers surely would have posted them to the internet, right?

To be clear, mono bass can sound great, and it's often the best and easiest way to get good bass in some rooms. So as compromises go, accepting mono bass is a small one.

Hello lemonhaze,

     Thank you for using a very interesting example to confirm this likely principle.  I understand your comment about a signal generated 41 Hz fundamental tone not being locatable since it lacks the necessary overtones.

Thanks,
Tim

Seems that the term non- directional is getting mis-interpreted also. The low frequency sound waves from a subwoofer emanate in all directions and although seemingly an oxymoron is called non-directional because of that fact. As opposed to high frequencies that emanate from a tweeter in a single and focused direction.

soundspectacular,

     Yes, I prefer the term omnidirectional, as opposed to non-directional, to describe the dispersion pattern of deep bass sound waves being launched into the room from a bass driver, whether from the main speakers or a sub.
     The difference between this and how the midrange and treble sound waves are so much shorter and are dispersed into the room in such a highly directional manner, couldn’t be more stark.
     The truth is that bass sound waves behave very differently than midrange and treble sound waves behave in our typical domestic-sized rooms. My experience has been that it’s much more difficult to get the bass sounding right in a room than it is getting the midrange, treble and stereo sound stage imaging sounding right.
      Due to the above, my system system building philosophy has evolved to the point that I now consider my system as 2 systems: A Bass System and an Everything Else System.
I      like to install the Bass System first in the room, before even bringing in and setting up the main speakers. I use 4 subs positioned in a distributed bass array (DBA) configuration since it provides optimized bass performance and does so throughout the entire room, which is important to me but may not be for others.
     If an individual only requires optimum bass performance at the primary listening position, however, very good results can be achieved utilizing just 1-3 subs in the room, provided they are positioned and configured properly in the room and in relation to the LP. In general, the more subs used in the room, the better the bass performance.
     Once the bass is sounding very good in the room, the final step is to position the main speakers in the room, and in relation to the LP, to optimize the midrange, treble and stereo imaging performance, which in my experience, is typically much easier to get sounding right in the room than the bass is.

Tim

👍 bass is Omni not non directional. 

So many confusing terms and uses.

Stereo recordings may not have special attention to the bass, so yes, it could be recorded in stereo.  Especially with purist, 2 or 3 microphone recordings, re-mixing the bass so that both L and R speakers had equal bass output is not something every mastering engineer thinks about. HT is very different.

The reproduction of the lowest octaves is omnidirectional due to the ratio of the wavelength to the driver.  You could make a directional bass driver, but it would be 10' or more in diameter.

The human ear / brain mechanism cannot place 80Hz and lower frequencies in a stereo sound field if the following conditions are met:

1. Lack of room rattles or other noises which can clue the brain in.
2. Equivalent room mode excitation/reinforcement.
3. Steep enough low pass filter to prevent higher frequencies from playing through.
4. The listener is placed reasonably central to the stereo speakers.

As a result a single subwoofer, properly integrated into a system (which is very rare) is not audible as a subwoofer nor can it's output be placed while listening from a fixed location.

The only clue in my listening room if my 1 subwoofer, placed stage left, is on or off is the bass extension. If you don't have that experience it's not because you have magic ears.  It's your room or the subwoofer integration.

Lastly, your main speakers will sound much better if  you high pass them at 80 than at 40 Hz.

Thanks for coming to my TED talk.

Erik

Lastly, your main speakers will sound much better if you high pass them at 80 than at 40 Hz.

Depends on the room, main, sub and processing available. My mains are -3dB @ 31Hz measured pseudo-anechoic. ≈40Hz integrates better than 80Hz.

When I used Spica TC-50, ≈90Hz.

The clarity obtained by LF attenuation in the mains with good subs should not be ignored:

1. Increased apparent amplifier power
2. Reduced voice coil heating which preserves XO frequency to the mid driver.
3. Reduced IM & THD in the woofer
4. Reduced current demand and its consequent mid & tweet modulation.

Tim ( noble101), yes, it does get better as you add subs. I couldn’t believe how much improvement there was adding a third sub after already getting the improvement of adding a second. My front subs have to go to the inside of the mains because there is an opening to the entryway on the right and an opening to a hallway and a sitting room beyond that on the left. Open floor plan and basically no corners either in the front. So that may be one reason for a dramatic improvement of the third. Don’t know if I’ll add a fourth.

What measurements establish the “improved bass”?  Improved in what way?

Just  wondering.  Is it just more? More  extended?  Flatter response ?  Different frequency curve?    What exactly is different than prior?

I have two twin-18” subs; run in stereo. 

MAPMAN -
It definitely does not get better because there is more. These guys you see on YouTube ( some considered influencers ) with multiple subs primarily in their theater systems are going for more bass and sound pressure. I guess if you just want to impress people by making their bowels move and shock the crap out of them ( pun 👍 ) go ahead and get your kicks that way.
You’re not getting more  bass if you have set things correctly. You can get more if you don't mind it being out of balance with the upper end but that’s not the way I listen to music or movies for that matter.
What has happened for me ( doesn’t mean it’s going to be exactly the same for anyone else in their room/configuration ) is that with two subs there was better blending ( horizontally ) without the perceived location issue derived from one sub. But, then the bass ( especially kick drums ) were overly emphasized and got just so centered that it was almost the only spot many of the lower frequencies were being placed. Unfortunately I have to set my front subs to the inside of my mains ( no choice ) so that influences the issue.
But when I added a third sub, wow!! Game changer and now I’m elated. The low frequencies are completely balanced in every way with the rest of the music ( frequencies ). There is absolutely no sensation that there are subwoofers ( external speakers from the mains ) and the bass is just part of the music ( heavenly ). The bass is still centered ( that’s the way it was mixed by the engineer ) but it spreads further horizontally and very naturally ( as I would perceive natural ). It fills the listening area ( I’m not saying there is bass all over the room ), making  it smooth with no overemphasis anywhere. I feel the subharmonics without it feeling like they are ”hitting” me ( even with movies ). Not that it’s due to multiple subs but I’m relaying that you don’t get that type of issue because you have added multiple subs. I think there can be that perception from the hype of the bass centric crowd.
What amazes me is that the third sub is less than six feet ( behind me ) from my listening position and I don’t “feel” it even at higher volumes, it blends sonically invisible.
None of this would be possible to achieve setting up by ear ( well maybe with a couple of years of trial and error ). It’s only been possible with the implementation of the MiniDSP HD 2x4 and REW.  The full use of REW with its eq section ( room correction with parametric eq that is similar to Dirac ). Beyond that the MiniDSP offers delay options so after the REW eq you can make tone sweeps and see which delays ( or lack thereof ) on each sub is most beneficial ( or not ). This is the best $315 I’ve ever spent!! Sometimes technology truly is your friend.
Now there is quite a learning curve and definitely trial and error but it is more than worth it!! Some may consider themselves to already have achieved this but I’m confident that if you implemented the MiniDSP you would achieve even further benefits and results.

Thanks for that explanation.  Minidsp is the way I would  go for that as well. 

mapman: " What measurements establish the “improved bass”?  Improved in what way?

Just  wondering.  Is it just more? More  extended?  Flatter response ?  Different frequency curve?    What exactly is different than prior?"

Hello mapman,

     I agree with soundspectacular, that the bass in a room or system does not qualify as improved just because it's louder or there's more of it.  I consider more bass an improvement in an audio system only if it manifests itself in the capacity to accurately reproduce large and natural bass dynamics contained on the source material, whether the source material is music or LFE channel information for HT. 
     My goal for my combo system has always been improved bass quality, which I define as bass that is accurate and natural in tone, pitch and intensity as well as powerful, detailed and textured without any exaggeration.  
     I believe a flatter in-room bass response curve and deeper bass frequency extension capacity definitely represent improved system bass performance.  However, I've never utilized any in-room bass frequency response measurement equipment, tools or room correction hardware/software.  I do believe such gear and tools are generally very convenient and helpful once competent skill at their usage has been attained.
    Since I bought and installed my AK Debra 4-sub DBA system about a decade ago, my criteria for evaluating and gauging its effectiveness in my room and system has been purely done by ear and subjectively.  I'd be interested in measuring its in-room bass performance but, unfortunately, I currently lack the gear and skills to do so
    But I'm not very concerned about attaining the gear and skills for accurate room measurement since I know without any doubt, based on how it subjectively sounds and feels, that it represents the best bass system I've yet to experience in my room and system.  I honestly believe my system, formerly with the AK Debra 4-sub DBA and 2.7 mains and currently with 3.7i mains,  has performed so well that I consider it a somewhat miniature version of Magnepan's $30K, 30.7 4-Panel Dipolar Planar Loudspeaker System, click the link attached below for a description and review:

http://www.hifiplus.com/articles/magnepan-307-four-panel-dipolar-planar-loudspeaker-system-revisited...

     About 3-4 years ago or perhaps more, I attended an in-person, Wendell Davis led demonstration of the 30.7 system at Ovation Audio in Indianapolis.  Of course, the 30.7 was very impressive being auditioned in about a 30'x20' room with 8' ceilings and being driven by a single, very large ss Anthem amp (I forgot the model).  The overall system was very impressive.  Natural and powerful sounding with full range and powerful dynamics, very much like how acoustic music played live and unattenuated, sounds and feels when experienced live and in-person.
     But the most surprising and disappointing impression I heard and felt from the 30.7 demo came from its two very large, 6.5'h x 2.5'w each, what they call bass/ mid bass panels.  To be clear, the bass and mid-bass reproduced by these very large dipole speaker panels sounded and felt very powerful, dynamic, natural and seamlessly integrated with the system's two equally large midrange and treble panels.  But I could clearly notice that the 4 modestly sized, 2'hx1'wx1'd, subs of my AK Debra DBA system inconspicuously positioned around my 23'x16' living room,  roughly equaled the 30.7 system's performance in sounding and feeling powerful, dynamic, natural and seamlessly integrated with my system's two more moderately sized, 6'hx2'w, 3-way and full range 2.7 dipole panels, had a bit deeper and more realistic bass extension. This is proven accurate by the difference in the rated bass extension between the two systems: 20 Hz  rated bass extension for the AK Debra system vs 24 Hz rated bass extension for the Magnepan 30.7 system.  
     Not a huge difference but it was obvious to me the AK Debra DBA system. overall, outperformed the 30.7.  After the demo during a Q&A session, I described this difference I perceived and asked Wendell if he ever considered just paying a royalty fee per unit sold to Audio Kinesis for adopting their much less obtrusive, and more effective, bass array concept using 4 small subs instead of the two very large and dipole bass/mid-bass panels. 
     Too blunt and pointed a question? Perhaps, but he's a big boy so no big deal, right?  He responded with a confused look. a hesitant look around the 20 person audience and a rather quick point for the next question.  I like and respect Wendell but everyone could tell he was awkwardly avoiding the question.  I still wonder why?

Tim

Interesting. I have no doubt more subs set up well is better.  I have 1 Klipsch  sw308 I set up manually with kef ls50 metas using  a sound meter app and white noise to initially set things up to extend the bass to be roughly in  line with all the rest then fine tuned including phase by ear.   Simple and effective. Would never have arrived at the right settings by ear alone.  The bass is just right.  

Hello mapman,

      Funny, I have no trouble optimally positioning my subs in the room by ear, when utilizing the sub crawl method on each one sequentially, but I do have trouble optimally setting their phase by ear.
      I found it was much easier to optimally set the group phase on my subs once I turned off my main speakers.  The proper setting became much more obvious to me once I did this, I just set phase at the position at which the bass is slightly louder, more solid, more detailed and the most natural. 
     Another tip, which makes setting the proper phase on subs even easier to discern, is to temporarily invert the polarity on the main speakers (simply by reversing the positive and negative connections on each speaker's terminals), optimally set the phase control on the sub(s) and then swap the main speakers' connections back to normal. 
      This made a lot of sense to me once I learned that the phase and timing of sound waves are almost irrelevant on deep bass frequencies but critically important on midrange and treble frequencies.  Humans are much less sensitive to sound wave arrival times on deep bass tones than we are on tones over about 80 Hz.

Later,
 Tim

@noble101

I set it by ear initially based on what I thought the rolloff of the ls50 metas would be based on specs and reading and thought it sounded good. But I did not achieve my goal which was to fill in the low octave and leave what the mains delivered fine alone. There was a big bass bump from ~ 40-60 hz that was audible on most all tracks. The sound meter app clearly showed this. Room is not large, only 12X12 with lots of furnishings to help break things up naturally.  My crossover was way too high and the level way too low. Now things sound like full range speakers with extended bass. Much better though that is a subjective assessment despite the fact that the setup measures better now! You can only tell there is a sub on the tracks with extended bass to start with. I have full range speakers running in the next much larger room off the same system (no sub) to compare with.

@mike_in_nc , my solution to that problem is 1 slow the fan down, 2 change to a quieter fan or 3 disconnect the fan altogether and provide other cooling. It has a bigger processor and runs much faster.

Thanks to everyone who has participated. I’ve been reading a bunch of these DBA threads and it is causing me to seriously re-examine what I am currently doing with only one sub. For the single seating position that matters, it is invisible sonically, an REL B1 set at 23Hz with volume at 6/40 clicks, merely to augment small but deep floor-standers.

I did not hear a noticeable improvement in trying true stereo (L-R) subbing close to the speakers and went back to the single REL.

After reading and thinking, my mind (I prefer to be scientific) wraps around the DBA concept very well. I believe those who think they can localize the deepest bass are merely being fooled by other cues in their environment.

Needing at least a complete wave or more to identify pitch makes sense. Let’s throw out the ballyhooing over time coherency when you have to wait to even know what the first deep sound was…and your brain is moving off in other places already…

I’m now wondering (without any more spending) about trying three SVS sealed subs, two SB-2000s and one SB-300 in my 20.5 x 17ft deep room (with openings and canted ceiling) in place of the single REL (or two RELs with an old Storm III in my collection). Along with a really old Def Tech PF1500 sub I’m willing to make the music room best and give the extra subs to the dedicated home theater room (music rules).     Thanks again for the great discussion. Now I’m thinking.

 

Doogiehowser, people listening to my system have ZERO problem localizing 100hz. I use a stereo subwoofer system because I cross at 120 Hz 48 dB/oct.
Most bass is mixed towards the center. Because all the speakers producing bass are closer together than 4 feet and have exactly the same group delay they act acoustically as one driver. Because they stretch from one boundary (wall) to another they form an infinite line source. 

Those of you not using a high pass filter on your main speakers are missing out on a chance to significantly lower distortion in their main speakers. Just because a speaker is specified to go down to 40 Hz does not mean it stops moving at 39 Hz. It can’t project frequencies below 40 Hz but, it is still going to try , wasting power and increasing distortion. I would suggest spending some money on a decent crossover instead of buying cable elevators.

By Jove, I think he's got it! 

Only what you should do is add 3 subs to your REL to make 4. The number of subs is far more important than what kind. I thought, according to the research, each additional sub adds proportionately less. So my plan was to build 4 to replace my one Talon Roc, which would then be sold. My plan was going fine. Removed the Roc from the room, put the 4 subs in, heard the vast improvement.

But then before selling the Roc I thought what it would be like, put it back in, and there it stays! Either it was more than the predicted 25% improvement, or 25% is more than you'd think. Either way it was big enough to keep me running 5. Granted the Roc is two 12" monster magnet woofers in a ported isobaric cabinet. A much better quality sub than the ones I built. So quality does count for something. But numbers count even more.

   doogiehowser        "You can't localize 100Hz"
I see you are new here you may want to explore, study, and read some more because 100 hz is very easily localizeable and this can be easily revealed, shown, and demonstrated in tests that are readily and easily repeatable by others wishing to learn the facts.

What about this:

Subwoofer Placement – No, You Can’t Put it Anywhere | News & Views | Ohm Speakers | Custom Audiophile Speakers for Music & Home Theater

Decades ago I was a partner in Audio Tweakers, Plantation, FL

We did a big 2 day event inviting local audio club

We were promoting Nearfield Pipedream speakers and had the 18s + 2 subwoofers in an awesome converted garage. George Bischoff was there representing Nearfield and set them up.  His sub placement was not good at all. Judd Barber (Joule Electra) was in the room with me when I asked George about the sub placement. He replied, it doesn't matter, as sub bass is non directional. When he left the room I moved them until they integrated. Judd looked at me and said WOW, I never knew otherwise.

hth

doogiehowser " I see you have been here a long time. Perhaps too long and have been brainwashed to accept anecdotal reports and poorly implemented experiments as fact."

No I conduct my own research, experiments, and explorations you do not know who you are talking to hear you might want to read some of my prior posts.

"We obviously have a different definition of the word fact"

No there is only one definition of the word fact it is true it is immutable it is not open to debate and you will have to accept it (or look very silly in the process!!)

"but feel free to keep using yours"

I do not need your approval, permission, or acceptance to post here no one does this group is governed by moderators


"I would highly encourage you to research the vast amount of facts (real facts) regarding localization of low frequencies."


I encourage you to do your own research on this topic it is so easy to prove that 100 hz bass is localizeable.

There are circumstances under which a pure 80 Hz tone can be localized and circumstances under which it cannot. Outdoors or under anechoic conditions, yes. In a home-audio-sized listening room, very unlikely. This is because the reflections start arriving before the ear has time to distinguish the first-arrival sound. But notice that I specified a "pure" tone - no additional energy north of 80 Hz.

There are conditions under which a subwoofer crossing over at 80 Hz can readily be localized. Crossover filters are not brick walls, nor do they attenuate the driver’s inherent harmonic distortion (because it occurs after the crossover), and both of these can result in audible and localizable energy north of the crossover frequency. Also if the output from the subwoofer arrives before the output from the main speakers, the subs are more likely to be heard as separate sound sources. And of course if the main speakers are turned off, the subs are far more likely to become localizable at some volume level because any (virtually inevitable) energy they pass north of 80 Hz will not be masked.

If the subs must be crossed over up high, and/or if they have a gentle lowpass filter slope (1st or 2nd order), probably best to keep them near the mains or at least make sure the output from the mains arrives first.

Imo, ime, ymmv, etc.

Duke

It seems to work well almost regardless of how the subs are laid out.

Geddes, a DBA progenitor, has several pre-conditions before the above statement is true.

For a simulation comparison of the effect of moving DBA subs in a room and system similar to the claimants, see http://ielogical.com/Audio/misc/DBARoomSim.php

Duke nailed it.