I don't do much commercial but I have gotten a few calls for bars and such. Some of these places on have 2-4 speakers per zone. If they numbers stay low and the load on the amp is safe can i use 8 ohm solutions? I mean most of these places are run on crappy speakers selectors as is.

I don't believe it HAS to be, its just easier both for wiring and the fact that the equipment is better designed to run all the time. With an 8 ohm system you will be running a lot of wires back to the head end, so more time and material to run the actual wiring. With that said, I have no experience with wiring a restaurant so I could be way off. Come to think of it, why did I post?

I prefer 70volt. Most places want nearly as cheap as possible and want minimal speakers. Then you get the call back later needing more speakers. Easier to add them in most cases with 70volt. Plus there are many options on the amp side with inputs for mics and such. Another reason is space. If it is a small place and not much room or tons of power needed you can get some very small in size amps which makes for easier placement.

It depends on what the job is, what the expectations are, and more. To answer your question, no. Restaurant jobs do not need to be 70 volt.

There are a number of helpful people in the industry who can help provide specific insights to your specific projects. You may want to check with them. Like the saying goes, you can ask google and get a million answers. You can ask a librarian, and get the right answer.

Long wire runs? If so, it's not a bad idea to use 70V. Off number of speakers? Ditto.

Sure makes most projects easier to do as 70v systems. Especially if it mostly be background music and paging functions are needed.

8 ohm systems need to be wired so the load on the amp is 8 ohms. That means you can use 1 speaker, or 4 speakers, or 16 speakers.

The four speaker setup is speakers A and B in series to make 16 ohms; speakers C and D in series to make 16 ohms; those two combinations in parallel with one another to make 8 ohms. And, since four wired this way are 8 ohms, four such groups wired similarly with one another is also 8 ohms. It's called series-parallel, but that term sounds WAY more flexible than it really is. A slight bit of flexibility can be gotten by wiring for four ohms.

But 70 volt speakers? A recent restaurant we did has one speaker in each bathroom and another in the office (A, B, C). The main eating area is not too large and three speakers are perfect for that (D, E, F). The rest of the place is fed by four speakers (G, H, I, J).

Here's where it gets tricky. We want a volume control on the single speaker in the office. So we put one in. Another VC on the pair in the bathrooms. Another on the eating area... and that area has two ceiling heights, so one of the three speakers must be louder than the other two to make the volume the same across the whole area. The rest of the place is on yet one more volume control.

With 70 volt, this is a piece of cake. Selecting a different tap for D makes it louder than E and F but it still goes up and down in volume with them. The office can turn the sound off if they need silence. All of this is impossible with 8 ohm wiring setup.

Better yet, if it turns out that a little fill is needed somewhere, one more speaker can be added. Try doing that with an 8 ohm setup!

If the issue is that 70 volt costs more, learn what products are good and take a chance on buying on ebay. Restaurants are forever being built and going out of business and perfectly good product is available... if you know what to look for. You can tell your client that you're saving them a ton of money if they will accept that the product is not new, and they will probably go for it.

Does 70 volt cross the line from "low-voltage" to "high-voltage" thus requiring a Electrical license?

Fred the "librarian".

Will smack you down if you make too much noise... :-)

In the state of Washington that threshold is 95v.

Ringing telephone line has about 90VAC.

Pretend that you're working on the 70V system while it's off and then you have 0VAC and therefore still qualify for the low energy classification. :-)

Also, many commercial sites the ceiling is considered a plenum area therefor requiring backboxes on speakers.

More 70volt speaker options with reasonably priced backboxes.

Jon,
I was in your boat few years ago.
My only exposure was 8Ω residential.
I had a job where 70V would be 'nice'.
Once I talked to Fred's people and few others, I was convinced that it was the way to go.

Call me if you wanna chat.

No.
To begin with, it's limited current -- that high voltage ensures that the amp won't output enough current to weld or, in most cases, to start a fire.

Next, 70 volts is not a number chosen completely by accident. There was some important spec in the past, that I don't know about, regarding 100 volts. It may simply be that 100 volts was the original choice of a system like this; I don't know. Now, the square root of two, divided by two, times 100 volts is 70.7 volts, or as we call it, 70 volts. If I didn't have to go earn some money right now, I'd search out more details because now I want to know!