Why does pulling out main speakers from wall improve sound?

Great discussion. Much good info. Varies much between speakers but the answers that addressed “baffle step” ring with me (see what I wrote there). As a Wharfedale Linton Heritage speaker owner, I’m a fan of the current wave of throwback big boxes…with the right distance from the back wall and a little toe-in they seem like best of both worlds between crisp imaging and rich tone.

It also lowers the noise floor. Like each and every time your audiophile friends come over to listen to music and say: "Hey, you really ought to move those speakers out away from the wall".

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@danager :  My issue is the bass sounds so much better when I stand up. 

I had that experience before too.  What I found is that my speakers were too far from the front wall.  It took me a couple of days of effort positioning the speakers in 1/2" increments to finally get them dialed in.  That includes the distance from the side walls too.  The crazy thing is, once I got them dialed in, the bass was nearly uniform all around the room- not just in the listening chair.  A good CD for evaluating the bass is Stanley Clarke's East River Drive.  The first track has a double tap of the bass drum.  When I got everything right that drum sounded good, not muddied to almost inaudible- except when standing up.

+1 @tonywinga 

You are balancing boundary reinforcement (getting close to the walls), with SBIR (cancellation from front wall reflection), and room modes. @bigtwin , Focal appears to be attempting to at least balance some of that in their formula, but as you noted, it may result in unrealistic values for many listeners.

@sc2, it is a little more complicated than what you have indicated. The distance they gave you appears to be to be outside the 10msec critical early reflection time. That may add a low frequency bass suck out (~50Hz). For many, even with a dedicated listening room, that may be too far into the room.  That gets us back to the speakers being closer to the front wall, the front wall heavily treated for reflections, and using equalization to address boundary reinforcement.