flat speaker quandary

(Just a suggestion) This could be a very expensive pursuit. Before spending too much money, go listen to your ML3's at a dealer who thinks they are set up well in his shop. If they sound like they do at home then it is unlikely any amount of tweaks will help you. Before jumping back to the maggies, go listen to some other systems. You may find something entirely different. I personally went from Magneplanars then to Soundlab (electrostats) and finally to some omnidirectional radiators and am very very happy.

Though I have no useful information regarding your speakers, I thought I'd suggest that I have found cables to be very important with an ART DI/O. Most recently I've used Cardas Lightning 15 coax, Audience AU24 coax, and Audience Conductor coax. Each is an excellent digital cable but the sound one gets is quite different. The Cardas is warm, well balanced, with high frequency detail. The Audience cables, however, add a little magic IMO. The AU24 sounds very natural, has a solid low end, and what I'd call an open sound stage. It has the most audiophile-like sound. The Conductor might be called darker but to me is even more magical with the DI/O bringing out the warmth that I love (at least with my equipment: CAL Delta, ART DI/O, Wright pre, Korneff SE45 amp, Lowther DX3 speakers). Especially given their price, I'd give the Audience Conductor digital cable a try. Don't make a jugement during the first few seconds. Give the music a minute or so to draw you in. (I also like the AU24 speaker cable and have rewired my custom cabinets with Audience hookup wire.)

Nick, I think Audiokinesis and Onhwy61 may have hit on something. Others also hit on a few issues. I own older Maggies and full range stats. I have also heard the SL3 but not in my house. The first time I heard the SL3 was with a Evo power amp. I was impressed. I know the room I heard them in was smaller than yours. The second time I heard the SL3 was at a Tweeter store driven by B&K. It imaged well but I can't imagine any buying them based on what I heard. They were sterile, cold and strident.

Audiokinesis spoke about the drop changes between a point source and a line source. I haven't measured it but he may be right. The ML's don't drop nearly as fast in level as does a point source. I have measured the ML in my room. My room is the same size as yours but I use physically bigger speakers. I use my ML biamped most of the time and adjust the woofer to my listening position. In my room every speaker has to conform to the same listening position. I don't have a lot of seating options. When I switch to my old maggies the listening position is the same but usually the speakers have to be in slightly different positions than the ML. Also my ML's have bigger panels than yours and may be harder to place. My maggies are also bigger than yours and are even harder to place than the ML. it usually takes weeks for me to get the Maggies right.

My basic points are: 1.Your amp could be the issue. ( I don't know the DNA1) 2. The speaker could be too small for the room. 3. To fix this problem could be an Odyssey (no pun intended) and certainly expensive. 4. The speaker could also be showing the weaknesses in your interconnects.

I see your points...

1. my amp
possible, but likely not. The McCormack DNA-1 is regarded as a very powerful, High Current amp (185wpc at 8ohm). I've been told that this is a great amp for ML's and Maggies alike.
However, it does not sound anything like the B&K ST-140 I upgraded from. I *loved* that sound. Very warm and punchy. Unfortunately for me, I upgraded both the amp and the speakers at the same time so I dont know who's to blame! I could easily get another old B&K amp w/that characteristic sound they had. Like a ST2140, for example. Those are relatively common and 1/2 the price of my McCormack.

2. Speakers too small for room
Probably, but sitting in front of them it doest appear so! They are pretty big....
I pulled them out into the room a little more, and that both helped and hurt my sound. Now I hear the room more. I can hear an echo of sound gathering behind the speakers. Bob Dylan sounds like he is hiding behind one of my plants!

3. Odyssey....I wish.
Why did I buy the SL3? I fell in love w/the ML sound after a tweeter demo of the Ascents (driven by B&K) and it was freaking monsterous. That demo sat in my head stewing until I scheemed a way to buy some of these marvelous speakers. I was hoping that the SL3 would be close in sound to what I heard from the Ascents. Not even close.....bummer.
So, trying to make due with what I ended up with

4. Interconnects...
I'm sure this is an issue, but I'd really like to borrow some modest cables first before I plunk down several hundred on the ones i've been spying (boulder cable M-80s). They will come eventualy, just for piece of mind.

Still, i'm tempted to go back to what I liked. Bigger Maggies and warmer amps.

Nick, if you really loved the sound of your previous system, then no amount of tinkering will make the ML/McCormack sound like Maggies/B&K. It might actually be cheaper for you to admit that you have made a mistake and go back to what you had. There's a good market for both the MLs and the McCormack. They should be readily sellable. A good card player knows when to fold.