My experience adding subwoofers to 2 channel

@noble100 if it wasn’t clear let me try to clarify it for you.

1. I’m building subs with 10" drivers for use as either a DBA or line array. It’s nice to have choices.

2. My active crossover has LP and HP filters set at 100 Hz. So the HP output sends signals 100 Hz and above to the panels and the LP output sends signals below 100 Hz to the 4 subs. Direct drive amps power the panels, a solid state amp or moderately powered tube amp with good damping powers the subs.

3. My current subs use 8" drivers in a tightly stuffed 0.3 cu. ft. box. This was done to insure the resonance of the driver was above 100 Hz. If I set the crossover points to 150 Hz on my filters this would be an issue but since I’m using 100 Hz and anything below that is sent to the subs this falls below the resonance so it’s a good thing. I should note that this was designed by Roger Modjeski for his ESL speaker system and the subs easily extend down to 30 Hz. If you don’t know who Roger is look him up, his experience and reputation speak for itself.

I tend to think at this point you just might have an issue with anyone who isn’t completely devoted to the DBA as you are. At least I can say from experience I have used the DBA and now trying a line array I have the ability to compare and decide what works best for me. My comments regarding Duke have more to do with my respect for him as a speaker designer, having owned his speakers at one time and exhibited his speakers at shows, than anything to do with DBA. Anytime I am at an audio show and Duke is exhibiting I make sure to spend time visiting the room. It’s always interesting to see what he is up to.

mijostyn states:

The reason clio is now feeling his bass is because his subs are now functioning as one driver and the arrival time (phase) is the same across the entire room.

This is of course impossible.

Clio I find your choice of a 4th order cross over at 100 Hz interesting. I can use any slope I want up to 10th order and can change cross overs on the fly. After eons of experimentation I settled on a 6th order low pass and a 4th order high pass all at 125 Hz. This is remarkably close. Is this coincidence or is this great ears hear alike? How did Roger modify the Acoustats for greater dispersion? Did he change the angles of the panels? How does Roger design his ESLs? Sanders uses a flat panel and crosses to a transmission line woofer at 175 Hz. I have not heard them myself. I talked to him via e-mail of doing a 7' 8" panel as a line source and crossing lower at 100 Hz but he was resistant to that idea. ML does the curved panel thing which highly limits their low frequency response to 250 Hz because of non linearities in the curved panel. Soundlabs uses facet panels in a curved array covering either 45 or 90 degrees. Acoustat used two, three or four panel angled arrays depending on the model. Sanders is the most selfish approach his argument being that there is only one listening position and everywhere else is background music. Plus as you increase dispersion you get into more trouble with room acoustics. He is right on both counts but it is nice to be able to provide a balanced frequency response throughout the room even if you can not provide an image especially when theater is concerned. I do not believe 45 degrees of dispersion causes significant problems with room acoustics. 

@mijostyn, I'll have to send you a photo showing what Roger did to create the wider dispersion. It basically involves some resistors, I believe three of them mounted near the bottom of the panel. I had to snip some of the wiring to put them in.

Roger felt that the Model 2, 3, X, and 2 + 2 designs were very good. So in designing his ESL panels he utilized the Acoustat panel material, as well as what he learned from Harold Beveridge and his own research to come up with his design. One thing Roger did not want was a big ESL, so it has a small footprint which means it's not very efficient, maybe 80 dB, and it doesn't go low, 100 Hz. He also did not want to mess with curved panels, so his are flat. His idea was to create a system made for bi-amping using his own direct drive amps and a solid state amp he would design with built in crossover (in our systems we both use the Beveridge RM-3 but given those are pretty unobtanium that would not be feasible for consumer sales). Roger much preferred the subs not be part of the panel structure, so they could be placed around the room, much like a DBA. He uses only 2 in his system.

My Acoustat Model 2s have slightly angled panels, that come to a peak in the front middle of the speaker and angle back from there. The panel sizes are the same as your 2+2 I believe. On each speaker one of the panels was removed and replaced with one of Roger's from an early prototype of his speaker which had the same exact size panel. The other panel is stock. I can set the speakers up so Roger's panel is on the inside or outside (which is how I have it now) and I have definitely noticed a difference in imaging when swapping positions.

As a side note I just got my Atma-Sphere system set up again today and at some point I will probably bring out my Quad ESL 57 to use with the M60 amps. I like this combination as well, although I don't think the line array will work with 57s, so I'll probably go back to a DBA.

 Helloclio09,
     
     My perspective is that the DBA concept is one of several solutions for those looking to add or improve bass response in the 20-200 Hz range in their systems.  You're correct that I have a certain devotion to the DBA concept solution.  This is probably due to it being the solution I researched the most, the solution I have significant personal experience utilizing in my own system as well as the one that has currently worked the best in my system and room.  
     I realize my previous experience was limited to experimenting with single and dual sub solutions in my system, but I learned that 1 sub is better than none and that 2 subs are better than 1.  Both restricted good bass response to the listening position area and I perceived the bass from both as being slower, lagging behind and disconnected from the rest of the frequency range being reproduced by my fast and detailed Magnepan 2.7QR planar-magnetic speakers.  However, I noticed adding a 2nd sub did begin to make the bass seem smoother, a bit faster, less lagging and better integrated with the main speakers along with more impact and better dynamics.  With the 4-sub DBA, everything improved significantly.  The bass was very detailed, smooth, impactful and dynamic without any sense of lagging behind or being disconnected from the main speakers.  Also, this excellent bass response was not limited to just the listening position area, it was equally good throughout my entire 23' x16' x8' room, including from all 6 seating and viewing positions within it. 
     So, yes I do admit I have a certain devotion to the DBA solution.  But I'm not naïve or close-minded enough to believe it's the only or even the best solution.  I haven't heard a line array bass solution and would prefer, as you apparently do, to personally experience any and all promising bass system solutions before declaring any particular one the best.  
     Unfortunately, I'm precluded from personally experiencing a good line array setup in my system due to a lack of a dedicated room and my wife's preference for our living room front wall not resembling the stage at a 9 Inch Nails concert.  As all Audiogon Forum regulars know, however, the next best thing to personally building and experiencing a bass line array system for yourself is to listen very closely to the impressions of someone else who has.  Which is why I'll be trying to follow your posts on your custom line array system and impressions closely.
     I also have some comments and questions concerning your last post and your numbered clarifying descriptions of your system and future actions and plans.  But I've blubbered on too long already, so I'll include those in a separate post soon.

Thanks,
Tim