Speakers with no rear wall, better or worse sound?

Some well intended but misinformed suggestions here with reference to the goal of Avalon Acoustics. I think you already understand the basic principals of thirds as described in the Avalon manual when considering your own room.

As simple as it's described in the manual, if like me, you're dealing with an irregular shaped room it will take a degree of trial and listening. The right recordings and speaker mobility during this period of adjustment can be your biggest asset.

After months of this I was sure I had found the magic placement only to have a friend who is very experienced with Avalons separate the speakers a few more inches and add 1/4" of toe-in and bingo. The sound stage seemed to surround as if the timing of reflection found the listening position optimally. In the end it takes someone who has experience with the particular speakers potential to wring the most out of your room.

The affect this had on the speakers bass was also a result of timing and not about an increase or decrease in bass. In my case (or my taste) the addition of two small Velodyne subwoofers to blend seamlessly and control the lowest octave also had the effect of adding size to my room.

Good luck with it.

I don't know whether it's physics or psychoacoustics, but the only way I can perceive soundstage depth with any real effectiveness is by positioning my speakers as you suggest, Hickory. Bass response is fairly easily addressed by changing the proximity of your head to the wall behind you. That does pretty much the same thing as changing the proximity of the speakers to the wall behind them.
-Bob

Thanks to all for the insightful suggestions. At a minimum, I have a few other considerations that do not involve major construction. I do not believe that bass in the current set up is lacking, so building a new wall may mess things up with respect to null and re-enforced modes as suggested by Josh358. Also, for Vicdamone (PS. I have a couple of records of the 'original' Vic Damone) I have spent countless hours playing with toe-in with my Avalons and with great benefit. I used to be disappointed in the soundstage width, in particular, which is currently much improved from all of the tweaking.