My experience adding subwoofers to 2 channel

 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

I want to add my subwoofer to my stereo system, I run the DAC directly into my amplifier. The Dac has a volume control, and the amplifier is balanced with DB25 connectors with pass-through.

Has anyone had experience here with an output decoupling transformer and summing two channels?

Oh and if you really want to clean up your sub sound, put springs under it.
Yes for real, it stops the vibrations going into the substrate and back up into everything you don't want to vibrate, including the sub woofer that created the vibration.
Townshend Audio in the UK have plenty of scientific style videos showing the benefits of seismic isolation.

clio09,

In my last post I stated I had some comments and questions concerning your last post and your numbered clarifying descriptions of your system and future actions and plans. Here’s your post with my comments and questions added:

"@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."

I agree, choices and options are nice to have. My four Audio Kinesis Debra DBA subs all have 10" aluminum long-throw drivers. These work well in my DBA system for music and ht, providing sufficient bass that can be felt as well as heard. These subs are ported but come with port plugs if you prefer to use sealed subs which some claim perform better on music.
.
My audio enthusiast friend, who assisted me with my DBA setup, and I both agreed that we perceived the bass as very similar whether run as sealed or ported subs on both music and ht content. There was no clear advantage we perceived on music content gained from utilizing the sealed sub configurations with the lone exception being we perceived the bass as slightly more extended running the subs as ported. We were both curious on whether using subs with 12" drivers would allow even further extension of the bass response along with increased dynamics and impact without compromising the excellent speed and resulting seamless integration with the main speakers.

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.

I’m very curious about which moderately powered tube amp with good damping you use to power your subs?
I wouldn’t even consider a tube amp to power subs due to their generally low damping factors and their resulting poor ability to firmly control the movement of dynamic cone drivers, especially the precise starting and stopping required of larger and heavier bass drivers in subs. Solid state class D amps seem to me to be the ideal solution for driving subs; very powerful with extremely low distortion levels, great transient responses and extremely high damping factors that often exceed 1,000. They’re also smaller, lighter, less expensive, require less maintenance, run much cooler and are tremendously more electrically efficient than tube amps.
Sorry, but the use of tube amps to power subs really perplexes me. You must have a good reason you’re not utilizing class D amps, right?

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.

A sub with a single 8" driver tightly stuffed in a tiny 0.3 cu. ft. box that extends down to only 30 Hz? Can this small creation even be accurately described as a sub? Please excuse me, but as a sub I think this can only be accurately described as pathetic, feeble, impotent and kind of unintentionally funny.

Tim

@noble100, The amplifier is the Music Reference RM-200, 100 watts per channel, damping factor of 10, can drive a 2 ohm load (it’s a favorite amp among some of the Martin Logan crowd). The other amps I use are vintage Luxman and Accuphase amps. For solid state I don’t bother with Class D, was never consumed with mega watts, and much prefer a high current Class AB design which is more suited to my needs. Also, the 8" drivers I use don’t need much in the way of damping.

As for my subs being feeble, sure no problem, we all have our opinions. Glad I could amuse you. However, I don’t listen to my music loud, I don’t do HT, and I’m not consumed with the last octave in the bass. As I mentioned, the system was designed by Roger Modjeski and his reputation speaks for itself. The cabinets for the 10" drivers are going to be a unique design and the bass will extend lower, but again, bass has never been the primary focus for me. My set up does exactly what I need it to do and so far it’s doing it better as a line array than the DBA. Although I find both set ups to be very useful in creating smooth, fast, and un-smeared bass.

BTW - I hope you are not using that Dayton Audio kilowatt amp for your swarm.

Tim, actually clio has a 12 foot wide sub woofer which goes deeper than just a single sub. Remember drivers closer together than 1/2 the wavelength of the highest frequency you want to reproduce act acoustically as one driver. Larger subs will allow you to go deeper as long as the enclosures are appropriately designed. I am not sure were this speed thing came in. Bigger drivers with appropriately sized motors are not slower but as the size and mass of the cone increases they become more difficult to control and keep their motion pistonic. All this is outlined by the driver's parameters which we use to design enclosures. I do not like ported sub woofers. They are more efficient and it is easier to get them to go lower but I have not heard one that to my ear is as accurate as a good sealed driver. The problem with sealed drivers is that you have to force them to go down using equalization and a lot of power. But the drivers we have today can easily handle it and with an amp with DF over 500, using a slightly over sized enclosure (Q around 7) you can get some really amazing bass. I personally see no use for drivers over 12 inches. In either a DBA or linear array system with 4 units you will never run out of drive in anything smaller than 40 X 20 feet especially if you keep the drivers up against a wall or corner.
Clio, I did not know you had an M60. What a tricky guy!. Just remove the Acoustats and put the Quads right down in the same place, same angle. Do both DBA and Linear Array and let us know what you think. The quads are point source which means they will not project power (volume) as well as a linear array. As you move back from the listening position the woofers will become progressively louder than the Quads. Down the block you will just hear the woofers:) As long as things are in balance at the listening position you are in business. Even in a DBA arrangement if you can keep the woofers closer than 5 feet apart that would be a benefit. Other people with lower cross over points could get away with more distance.
The 2+2s are nothing more than stacked 2s without the base. The angle is the same. If you could find another set of 2s you could make 2+2s out of them. I toyed around with the idea of making 3+3s but eventually I will go with Soundlabs. I think what Roger is doing is is rolling off the high frequencies at the outer edge of the Stators to make the panels effectively narrower as the frequency goes up which would increase high frequency dispersion. Making 2s or 2+2s disperse is IMHO fruitless. Just stay in your listening position and enjoy.