Audio Systems: medical office, atlas soundolier, combo preamp

Question
I am interested in wiring my office for background music.  My music source will mostly be my iPod and maybe some CDs.  I have 6 different rooms (3-8x10, 1-15x8, 1-14x11,
1-17x21) all with 10' ceilings.  I would like each room to have its own volume control, which can either be in each room or at receiver location.  I am trying to do this inexpensively. I need to know
1. how many speakers will I need
2. can I use commercial 70V 20W speakers
  (I found OSD-C1070V 8" speakers very cheap)
3. what type of wiring should I use
4. what are my options for volume control
5. what do I need in terms of receiver
6. given that the largest room will probably have a few speakers is this any concern for the power I will need
&. is there anything else I should consider???

Thanks, Donna

Answer
70V is the best way to do this on the cheap. I am not the one to ask about using very inexpensive 70v equipment since I am in the music business and sound quality is paramount. At the same time I can recommend manufacturers who make amplifiers, volume controls, the correct type of speaker cable, etc. If you are using iPods & CD players then cheap 70v will not give you the fullrange sound that iPods & CD players will afford you. Still even decent commercial grade 70v is very affordable. Receivers are generally consumer devices so you would probably be looking at amp pre-amp combos.

Here are the names of some of the recommended manufacturers:
QSC - amplifier (high end)
TOA - integrated amp/preamp PA (low end)
Atlas Soundolier or Lowell - Speakers - (low End)
Bose, Tannoy, JBL, - High end speaker
Audioplex - volume controls
Numark or Denon combo preamp iPod Dock, mixer

Cable should be 18/2 stranded for runs under 100 feet
16/2 stranded for runs over 100'

Since 10' isn't very high the rule of thumb is that the larger the diameter the speaker the more narrow the pattern. Smaller devices produce a more even distribution of sound. Distances between speakers are effected by their patterns. All professional speakers have pdf specifications showing their patterns. For example 160 degrees is a very forgiving pattern for distributed sound. It will give you smoother response of all frequencies covering a larger area. The distances between speakers can be anywhere from 10 to 20' depending on their size. The downside of using small speakers is that they lack low end. The fix is to insert an subwoofer somewhere in the chain. There are speaker systems made such as the Bose Acoustimass FS3 which are only available commercially and use 4" diameter speakers.

20W is a lot of power in a 70V system and may not be necessary if the system is designed correctly. For background music 5W may actually be sufficient.