Muffled voice in the back of stage?

I had similar trouble with a pair of Magnepan 12qrs. Sometimes voices were very prominent and on other recordings it sounded as if the singer was hiding behind the stage. It was a very curious phenomenon as the same recording on my Thiels had the vocalist upfront and center as expected.

I'll take a wild stab at this. Some 20+ years ago when I attended meetings of the local audio club, our club system used a pair of Acoustat 8 electrostatic speakers. The room where we met had an angled ceiling (like the front-to-back half of a room with cathedral ceiling), and it had a strange acoustic characteristic: with some recordings it created reflection/reverb that made music/voice sound like it was coming from above and behind you. By changing your seating position you could reduce this effect. So, I'm thinking that your Maggies, being a dipolar speaker like the Acoustats, generate a rear sound wave can cause strange propogation problems. You might try some room treatment (like Sonex panels) at key reflective points around your room, combined with changes in the amount of forward or backward lean of your speakers. If these approaches don't help, contact a local high-end audio dealer for the name(s) of companies that do acoustic room analysis and tuning. Hope this helps.

Its possible that whoever made the recording, did a poor job. Maybe they did al1right with the musicians on the front of the stage, and messed up on the rear.

Also, disconnect one of your speakers and listen to the one that's still connected.Then do the other speaker. If one side sounds ok and the other doesn't, it will help isolate the problem.