Why the fascination with subwoofers?

mijostyn:
 "Hey Noble, Real Bad Idea. I love Maggie 20.7s but adding two more bass panels is just going to give you a lot more of no bass.(below 40 Hz)
Dipoles make crappy subwoofers. There is this myth out there that you can not mate a dynamic sub with a dipole bass panel. That is because most are trying to do it the wrong way based on more mythology. I have been using dipoles exclusively since 1976. I would never live with out a sub woofer. There is no other way to reproduce that visceral you are there experience."

Hello mijostyn,
     
     I currently agree with what you posted.  I think we both know for certain it's possible to seamlessly integrate powerful dynamic subs with dipole panels because we've both done it in our own systems, in our own rooms and with our own dipoles. We both know how to do it well, although in somewhat different methods. 

     You're also likely correct that dipoles make poor subwoofers.  But my response, to trying Duke's concept on dipole sub arrays built into the front and rear walls, was hypothetical and prefaced on me winning the lottery.  Meaning I'd have the disposable income to give it a try.  If it didn't perform better than my current dba, I'd probably just use a custom dba with 4 dynamic subs that could each reproduce bass accurately well below 20 Hz.  I do enjoy visceral bass in music and ht.

Thanks,
Tim    

Hello hifidream/Steve,

      Nice to hear of your daughter's successes.  I wish her the best.

     Thank you for taking the time to respond to my previous post.  You have assembled a very impressive custom dba system with very high quality Magnepan 20.1 main speakers.  
     It seems like you've taken the excellent dba concept to new heights of performance through the use of 2 Kinergistics tower subs, 2 SVS SB-16 Ultra subs, the Multi-sub Optomizer, the Mini DSP along with the dual dipole bass panels in each of your 20.1s. 
      From personal experience, I know it's somewhat difficult to integrate the bass reproduced by dynamic subs with the fast, smooth and detailed top to bottom sound reproduced by panel main speakers.  
     I understand the pleasure of having guests jump out of their seats from powerful and dynamic bass on both music and ht.  The ability of dbas to provide excellent bass response throughout the entire room, and not just at a single sweet spot, is the result of eliminating the perception of bass modes in the room.  This not only has the benefit of startling guests but also has the added benefits of increasing the sense of imaging depth, the details within the deep bass and better clarity from mid-bass to treble at the listening sweet spot.

Enjoy,
Tim

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