1.) When you say 'shop' do you mean an industrial work shop, or do you mean a retail establishment? Next, if retail, are we talking merchandise or food and drink?
2.) Next we consider the structure of the building. For example, are your ceiling closed, meaning sheetrock, wallboard, plaster, or perhaps suspended tile ceilings? Or are the ceilings open with rafters, beams, or trusses?
Each has different problems and different solutions.
3.) Are you playing the radio, or are you playing your own collection of recorded music? I think the public music license might be different for radio.
3a.) Do you foresee the need for any type of in-house PA system?
4.) We need to consider wiring. Is it possible to embed it IN the walls, or will it run along the surface?
5.) How many speakers do you envision needing?
The room is 7m x 11m or 23 feet x 36 feet. Again, the distribution of speakers depends on the nature of the shop.
But more so, the number and type of speakers will influence the number and nature of amps you need. If we assume you are intending to adapt common stereo equipment, then each amp can handle no more than two 8 speakers per amp channel. That means one stereo amp can feed four 8 ohms speakers. If you need more speakers, then either the wiring becomes more complex, or you need a second set of amps.
6.) Is this, in a sense, just going to be anonymous elevator background music? Or, will people actually be paying attention to it?
7.) What is your projected budget for this music system? More than anything that will dictate our responses.
My concern about the ceiling was in determining if the speakers could be mounted on the ceiling or if they would have to be mounted on the walls. On the ceiling would give you better distribution of sound, but it depends on the height and the general structure of the ceilings.
As to the number of speakers, 2, 4, or 8 are easy to wire, but 6 is more difficult. Six speaker means 3 on each amp channel, and it is difficult to come up with a workable impedance with 3 speakers and at the same time keep the signal and the volume the same in all 6. To make this work, you would need 12 ohms speakers to start with, and while not non-existent, they are about as rare as hen's teeth.
However, two 8 ohms speaker will fall with in the impedance range of most good amps. Two 8 ohms speakers connected normally results in a 4 ohm total per channel impedance. That is, two 8 ohm speakers on each amp channel, for a total of 4 speaker on the system.
With four 8 ohms speakers (8 speakers total), you can use a combination of series and parallel wiring to make the total of 4 speakers per channel the same impedance as a single speaker. I have a diagram I can post if you want to see it, but it amounts to this -
- two 8 ohms speakers in series equals 16 ohms total
- you then take two gangs of those speakers and put them in parallel; two 16 ohm gangs in parallel equal 8 ohms.
The result of the 8 speaker (4 on each side) is an standard 8 ohm load to each amp channel.
Next, we need to look at the fidelity of the speakers you have in mind. For background music, they don't have to have super bass, so small bookshelf speakers like the JBL Control 1 or the Wharfedale Diamond 9.0 or 10.0 should be reasonably easy to mount, whether on the ceiling or the walls.
Curious what is your ceiling height , both to the beams and to the actual ceiling? If you have 10 foot ceilings then no problem mounting on the ceiling. However if you have 8 foot ceilings, that becomes more difficult. The problem with 8 foot ceilings is that the sound from each speakers has less room to spread out, and therefore covers a smaller area. Still, with enough speakers, this might not be a problem.
Also, what is above your ceilings? If there another floor on the building? How thick are the ceilings? It might be possible to mount in-ceiling speaker in the ceiling, but, again, that depends on the construction and depth of the ceiling.
As for amplifiers, you either need a tuner and integrated amps, or you need a stereo Receiver. I'm not sure what the schedule is for conversion of FM to Digital (DAB = Digital Audio Broadcast), but that might also be a consideration. You might want a FM/DAB as opposed to AM/FM tuner.
I don't see you needing tons of power, consequently any standard good quality integrated stereo amp in the 40w to 80w range will do. Though given the number of speakers, I would concentrate on something in the 60w to 75w range.
The next consideration is the location of the amp relative to the speakers. Generally, you want to keep the farthest speakers with 50ft of the amp. That is, within 50 linear feet of speakers wire. Likely for the room size you have, and just in general, 2.5mm² wire of basic quality will get the job done. This can cost in the range of £0.75 to £1.50 per meter and is available in bulk rolls of 25M, 50M, and 100M.