Thank's in advance.

In very large environments, there are almost always a number of sound sources. And there is a lot of area to cover, so coverage becomes the major focus. The installer has to use several subsystems to generate enough sound to be heard everywhere. This causes some interference problems that must be solved. The solutions generally involve placement, orientation and phasing. So in this application, you will find group delay becomes significant.

But if your sound system contains just a few speakers in your home, then the distances are probably pretty small and you probably don't need to worry about this too much. A bigger concern is room modes, which are caused by boundary reflections that act like multiple phantom sound sources some distance away. The best thing to do in that case is to emply dense interference to smooth the sound field, and the way to do this is with multiple distributed subs.

On the issues that happen when arrays are used for pattern control, you might be interested in paper written by Perrin Meyer called "DSP Beam Steering with Modern Line Arrays." It contains a lot of useful information related to the issues faced, including practical solutions.