Originally Posted by
anwaypasible 
the distributed system is basically one speaker channel.. and then 10-20-30-40 speakers or more connected.
grocery stores have 'em in the ceiling.
phasing issue... well there is more than one definition of the word depending on how or where the word is used.
insulated wire has come a long way since the cloth wrapped stuff from like 1930
the other phase issue is the final sound from the speakers in the ceiling.
there are typically three types of results:
1. you go in there and the audio from the speaker sounds like it is forward and outwards, as if glowing out from the wall
2. the audio from the speaker sounds like it is pushed back.. comparable to somebody with farsighted vision and thick glasses (their eyeballs look small behind the glasses)
3. in the middle between the above two is a spot where the audio sounds like it is one with the room, and looking up to find the speaker might not happen right away.
its 5 speakers from 5.1 (or you could not use the center channel and be with 4)
otherwise maybe one of the 7.1 receivers will upmix 2 channel to 7.1 and that could get you 7 speakers.
or the distributed system will get you more speakers.
i think it is easy to choose:
1. do you want gaps with less audio inbetween speakers or do you want the sound to be full? (kinda like light from a spotlight in the ceiling.. do you want the floor to be lit completely with the light from the spotlight or some circles on the floor and the rest of the room lights up with ambient light?)
2. do you want stereo sound?.. because stereo will sweep the room if you can hear the other channel.
if a hair salon went with stereo.. i would probably put a left channel on one side of the chair (not above it.. to the side , in the middle between two chairs) and then place the right channel on the other side of the chair.
if you dont want the speaker right above you, i would put the speaker in the hallway area in the middle of the room (typical of a shop where the chairs are on the wall each side)
that way the stereo effect will happen for all chairs (unless you run out of speakers.. but the speakers can be spread out until the gap is too quiet)
a distributed system has two choices:
1. there are no gaps of volume difference between the speakers, even standing under the speaker (or close to it)
2. there are easily heard gaps of volume difference between the speakers.
you could still get stereo sound from a distributed system.. but you would need one for the left channel and one for the right channel.
another big question is..
are you going to be there for the customer if they move or twitch their head because of some audio panning from one speaker to the other?
its a valid question as to whether the person moves their head or not.
or do you switch to mono and avoid it altogether?