Wire speakers in series? Mount on electrical box? (1 Viewer)

[Scott DeToffol]

I'm helping a friend wire his retail store with five speakers in the ceiling. The ceiling is way up there, probably 30 feet high. We have access to some scaffolding this weekend, which will make the wiring job easier. The ceiling will remain exposed.

These speakers will only be used for background music in the store. I'm wondering if it is ok to wire the speakers in series from the amp? Is there a gauge consideration if I do this? The speakers will be in line from the back of the store towards the front and I'd like to avoid having to run a separate pair of wires to each speaker.

The second question is about mounting. There are electrical double gang J-boxes available on the ceiling. Are there any mounting kits made to allow us to mount the speakers to the J -box?

We haven’t picked the speakers yet. I’m thinking of some type of outdoor speaker that will blend in with the HVAC and girders. Any suggestions?

Thanks for the help.

 

[Brian Fellmeth]

If you were doing four, it would be possible to reproduce the nominal load of a single speaker by wiring A parallel to B, then C parallel to D then put AB and CD in series. Or with 6 you could do AB CD EF (three parallel pairs in series) which would create a reasonable load. If you have to do 5, putting them all in series would work ok- might want to find 4 ohm drivers so the impedance would end up 20 ohms. In this configuration, wire guage is not important (sonically). Just don't go smaller than 21 guage. There may be building code issues however.

 

[Wayne A. Pflughaupt]

Scott,

I’ll tell you right up front that commercial audio is a whole ‘nother world from home audio, and the stuff you know about the latter will only get you so far with the former.

Generally what is used in commercial applications is a 70-volt system: An amplifier designed for this application puts out a high-level 70-volt audio signal. Each local speaker has a transformer that converts the signal to a lower-level one suitable for voice-coil. The transformer can be tapped at say, 1/4, 1/2, 1, 2.5 or 5 watts, depending on the volume level that is needed at each particular location. This system allows for multiple speakers to be connected to an amplifier easily and safely in a parallel configuration with a single cable run. Determining needed amplifier power is a simple mathematical accumulation of the number of speakers times the power they are tapped at: E.g., 25 speakers tapped at 2.5 watts requires a 65-watt amp.
Any small speaker suitable for wall hanging should be fine. Just keep that “continual duty” thing in mind and don’t get the cheapest thing in the store.

Regards,
Wayne A. Pflughaupt

 

[Scott DeToffol]

Fantastic information! Thank you Wayne and Brian. As usual, a few points of clarification are needed.

First, my friend is opening his first retail operation and cost is a huge issue, that's why I'm helping him instead of a professional.

It sounds like wiring the speakers in series is doable. I'll have two runs, one with three speakers and another with two speakers.

The J-boxes are not being used and have empty conduit perfect for running the speaker wire. This should keep the wiring fairly safe from others. I found some speaker mounts that fit on a single gang J-box.

I think we’re going to have to improvise depending on the type of speaker we get. I like the idea of clamping to the beam.

Thanks again. Any other suggestions would be appreciated.