As a live performer I am often set up against a wall in the middle of a restaurant playing easy-listening music with diners in front and on both sides of me.A Bose system is supposed to be able to generate a 180 degree even dispersion of sound from one array source but I wondered if this was achievable with a 3 conventional speaker cluster facing left, forward and right? I am aware that there are theoretically lobing problems as mono signal through all 3 speakers can produce phasing etc and I operate mono so everyone can hear the same thing. Any idea's?
There are a few things you can try, but if you are talking about the Bose Column system I am thinking of, I have used that and it does not do nearly what is advertised.
Stereo: This is the most common setup and your typical PA system. Even if you are running a "mono" source (a mic or instrument) a mixer will allow you to buss this to both channels of a stereo setup. If you position your speakers on either side of you about 45 degrees off center you will get a nice sound with good coverage all around. You may need to play with the angle but it will change from room to room.
3 Channel: I have used a few of these set ups and in small situations they don't really give you anything you cant get from a stereo setup. I have found them most advantageous when the stage is large to the point that your R/L speakers are far enough apart to create a noticeable dead spot in the middle. In this case the center channel can fill in there. 3 Channel also helps when you have a band and as you can use the center to make the vocals pop a bit more by pulling everyone else out of the center mix. If you are playing small shows in restaurants I would consider this over kill.
Phase Issues: While these do exist and every system has dead spots, this will change room to room and you will need to play around as you go from place to place. Moving the speakers left/right/up/down can usually fix the majority of these issues. In general this is what sound check is for. If you are alone I would advise playing some music from an iPod or something and walking around the space before hand to listen from different seats. I like to always play the same song so I can compare spaces and have a good reference point.
Related Reading (just to get some brain juice flowing):
This nicely outlines some of the history and development of stereo and why its used.
Here is an interesting article on 3 channel sound.
This might be worth a read but I have not looked that closely at it yet.