Why the fascination with subwoofers?

Noble, if they are built into walls they are no longer dipoles and trying to get the resonances out of walls is a nightmare. The limiting factor in all Maggies with a ribbon tweeter is the tweeter. It is a wonderful tweeter, some say the best ever made but it is delicate. Adding more panels is not going to increase the system overall output. I can't speak about sound quality because I have never heard it done. Quality first, output second.
The key with any linear array system is to keep it functioning as a linear array over the entire audio and subsonic spectrum so that power output remains even from top to bottom. There is always a weak link in the chain. In my case even with 800 class A watts at my disposal it is the satellite amplifiers. At that point I am putting out 110 db which from most peoples stand point is absurd. Comfortably loud is 95 db. At 110 db my subs are hardly working. You have to make your subs a linear array which you can do either vertically with two sub towers from floor all the way to the ceiling or horizontally with drivers all along the front wall from corner to corner. It is easier to control resonance in a smaller enclosure so I favor multiple small cabinets over one or two large ones. Your explanation of Q was excellent. I build my subs with a higher Q than usual 0.76. I depend on amplifiers with very high damping factors to control the drivers. This increases efficiency.  How many you need depends on the length of your wall and the crossover frequency you want to use. To take the most advantage of boundary gain two have to be in corners and the others along the floor wall boundary. I use a cross over of 125 Hz so the individual drivers have to be 6 feet or closer together. The wall is 16 feet so a total of four subs will do the trick. Because of boundary efficiency with room control I am flat down to 16 Hz where I roll the party off steeply to prevent issues with the turntable. If you want to use a higher crossover you have to space the drivers closer together. If you have a longer wall you will need more drivers. A point source system is different. If you used this type of sub array with a point source system as you backed away from the speakers the subs would become overpowering. As Atmasphere suggested a two sub system tuned to the listening position would work fine or if you wanted more even response throughout the room a "Swarm" would be fine. I use 12 inch drivers exclusively by the way. I am working on a new set of balanced force subs with octagonal enclosures made of 2" MDF. They are essentially a tube with a 12" driver in each end opposing each other, canceling out all Newtonian forces. Same Q. 

mijostyn,

      Very good and interesting information, thank you. 
      I'm very satisfied with the bass response in my room with the AK Debra 4-sub dba system, even though it's only capable of flat bass down to 20 Hz. 
      If I ever wished to extend the bass response down to 16 Hz, I know my best solution would be upgrading all 4 subs to ones capable of reproducing bass down to 16 Hz. I know my current bass system, with flat frequency response from 20-100 Hz, can only reproduce the majority of the entire lowest octave (16-32 Hz), but I'm currently satisfied with that since I currently play no source material with bass content below 20 Hz that I'm aware of.  
     My system goal is to reproduce bass that is accurate, detailed, dynamic, powerful and sufficiently extended to reproduce the lowest frequencies contained on any source content I choose to play. While I believe my current source material (Redbook cds, streaming services and 24 bit/96 Khz FLAC digital files) are limited to a deep bass frequency of 20 Hz in mono mode for various reasons, I realize Redbook cds and direct to digital hi-rez recordings are capable of capturing discrete L/R channel bass channel content at even deeper bass frequencies.  This would allow true stereo bass playback on recordings.
     Just to be clear, the walls of dipole subs front and back is audiokinesis/Duke's idea that he's never actually tried.  I believe it's best if he replies to your specific points about his concept.  
     I told him I'd pay for him to build me one in my new home if I won the lottery, which is not likely to happen since I don't normally even buy any lottery tickets. So, it's all currently hypothetical.


Tim

I think mids and highs are overrated too

b_limo: "I think mids and highs are overrated too."


    Excellent thread summary, Attorney General Barr.

DJT

@noble100 -- 

I'm not a Bass-Head but I admit I enjoy the bass weight and power that viscerally involves your whole body in the music or ht. 

I can relate to that - certainly. For bass to be able to be enveloping, effortless and visceral are vital aspects for bass to simply be uninhibited. 

But I also believe in setting the crossover frequency as low as possible so the subs only engage when required for accuracy and not for an artificial general system bass boost.

An "artificial general system bass boost"? I don't see why this would be the necessary outcome of a higher cross-over between the mains and subs. One may have a wider frequency span to adjust bass level and overall response, but to me - using an 80Hz cross-over - the goal is the same compared to using a lower XO: for the overall integration to be smooth and seamless. 

Perhaps one of the issues of using a higher cross-over point, apart from it being potentially problematic using several subs scattered throughout the listening room, is the thought of using a high-pass filter over the main speakers. This is understandable, I've been there myself, but I can attest to the positive outcome using a quality digital XO over the mains, and that any detrimental effect on transparency with a proper unit is perceived as zilch. Some may bark at this and claim such a component will inevitably have its say on the sound, and they may be right, but to which degree and in what context? Using a quality digital XO over the mains and high-passing them at at least some 80Hz have a plethora of other advantages that can easily (more than) alleviate a theoretically negative effect a given component may have being added to the chain:

WIN # 1)  Since you are now NOT putting in 20 Hz - 80 Hz into the mains you are not using up the available LF cone movement with bass, so the LF cone in your mains is able to play its higher freqs (up to IT'S crossover point) much more cleanly. You get an apparent 6dB or more dynamic range. You can play your system LOUDER, and also with less compression distortion in the LF driver when you're having that Saturday night dance party and you're playing urban bass technopop at 110+ dB. Really.

WIN # 2)  Since you are not putting bass into that same driver you are not Doppler modulating everything between 80 and 600, or whatever the next crossover point is. This means cleaner mids. By far.

WIN #3)  You are not sucking current out of your main power amp at low frequencies, so there is more current reserve to play those highs louder...

WIN # 4)  Since the cones aren't moving as far at the low freqs the driver itself is not generating as much back EMF therefore the damping factor and all of its issues are greatly negated. And you don't need to run silver plated cold water pipes to your mains as speaker wires because there is less current draw by the speakers.

WIN # 5)  Freqs below 80 are now NOT causing transient intermodulation distortion with the higher freqs (and vice versa) in your power amp. Cleaner still.

http://www.soundoctor.com/whitepapers/subs.htm

I've also discovered that bass quality is vastly more important than bass quantity. A leaner presentation without much extension is preferable to me than lots of bass if that bass is thick, colored, and sluggish. If the bass isn’t well reproduced, I think most would agree we’d rather not hear it at all. The poor bass performance becomes a constant annoyance and a reminder that we’re listening to a reproduction. 

Agreed.

I've learned that realistic reproduction of the majority of the bottom octave (16Hz–32Hz) doesn't require large woofers in large enclosures, 4 subs with 10" woofers in relatively small enclosures are equally capable. 

Equally capable compared to what? There are many iterations of using only a pair of subs that involves 21" units (or bigger) and/or horn subs that would leave 4 spread out 10" direct radiating subs sounding close to malnourished. Would 4x10" be sufficient in many listening rooms to many listeners? I believe so, definitely, but others would disagree, and it's not necessarily for them being "bass heads" as such; what is "realistic" to you may not be the case with others and their setups. 

It's also true that a system’s bass presentation affects such seemingly unrelated aspects of the sound as midrange clarity and sound staging. Thickness in the mid bass reduces the midrange’s transparency. A cleaner mid bass not only makes the midrange sound more open, it also lets you hear more clearly into the extremely low frequencies. Moreover, extending a system’s bottom end has the odd effect of increasing soundstage depth and our overall sense of the recorded acoustic, even on music with minimal low-frequency energy.  

I concur, only to add that these advantages are potentially more pronounced using a high-pass filter over the main speakers, for reasons outlined above. 

However, I'd suggest choosing subs designed for musical accuracy, not home-theater fireworks. Some subs exist to produce the highest possible sound-pressure-level at the lowest possible frequency for playing back explosions in film soundtracks. Others are crafted by musically sensitive designers with high-end sensibilities. Be sure which kind you prefer and are selecting.

I don't find musical accuracy and "home-theater fireworks" to be mutually exclusive. Watching Blu-ray movies I simply notch up the bass level by some 1.25dB's (some may prefer even higher HT-boost bass level). This "amalgam" of proficiency with regards to both music reproduction and movie playback I find is no doubt rooted in the specific topology, namely horns (a pair of 15"-loaded tapped horns, in my case). Horn subs deliver the most musical bass I've ever heard in being more refined, smooth, enveloping, dynamic and effortless than any direct radiating solution I've heard. Horn subs vibrate the air in quite an omnipresent fashion that gives the bass a floating quality even that's rather unique.  No multi-use of direct radiating subs can achieve the same, period, and predominantly it has to do with how the cone couples to the air. Horn subs take up space, though, and 20 cubic feet for 20Hz reproduction may be a hindrance for many, if not most audiophiles. A shame, really..