My experience adding subwoofers to 2 channel

clio09:
"My subs were built a while back, mijostyn helped me set them up for optimal performance in the line array. His subs have quite a large footprint, as do his speakers which are probably the best Acoustat model in my opinion. They line array per mijostyn is actually a semi circle as opposed to all of the subs being against the front wall of the room. A very interesting set up and one that does require some attention to detail. I appreciate mijostyn’s patient with me.

In my room the DBA did work well for my needs, and it wasn’t a difficult system to set up. My only nit was that my room constraints didn’t allow me complete freedom to place the subs anywhere I wanted. The sound was quite good though. I am embarking on building 4 new subs using a 10" driver and look forward to going to the audio show in Long Beach to hear Duke’s Swarm in person."


Hello clio09,
     
     I'm having difficulty following along with your posts.  From your post quoted above, it seems you're switching from using a distributed bass array (DBA) to a line bass array system for your Acoustats and with mijostyn's help.
     Then, in the very next paragraph, you state you're starting to build four new subs with 10" drivers and you're looking forward to hearing Duke's Swarm DBA system, which happens to utilize four subs with 10" drivers just like the four new subs you're about to start to building, at an audio show in Long Beach.       
     Don't you agree this might be a bit confusing to a reader, especially when you just stated you're in the process of switching from a distributed to a line array bass system?
    But the confusion continues with your latest post from5/27/19:
"I use low pass and high pass filters in my active crossover, Linkwitz-Riley 4th order 24 dB slope. One reason this was chosen is that we wanted to keep deep male vocals out of the subs. The other reason had to do with the resonance of the 8" drivers which we wanted to keep above 100 Hz. This is the reason for a 0.3 cu. ft. box which is stuffed tightly with cotton batting. The last reason has more to do with Roger Modjeski’s ESL design which only goes down to 100 Hz but that is irrelevant to me as I use the Acoustats which he modified to create greater dispersion, but left the rest alone, sort of ;)"

     Now you're discussing 8" drivers in 0.3 cu. ft. boxes stuffed with cotton batting that only extend down to 100 Hz?  Would this even be considered a sub and how are these 'mid-bass woofers' even relevant to either the DBA or the line-array bass system you're using?

     Can you please clarify?

Tim

@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.