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Cable sizing for Ceiling Speakers

Cable sizing for Ceiling Speakers

(OP)
Hi there,
We are having 6 W Bosch Ceiling Speakers in our Project. Where Route length from end to end is up to 1000 meters at some places. Please tell me what cable size shall be suitable for it. And how it can be calculated for a specified length.

RE: Cable sizing for Ceiling Speakers

(OP)
No, This is not for school...... This is for Our thermal Power Project

RE: Cable sizing for Ceiling Speakers

Transformer-fed of a 100V line (or 70V line), or direct fed? Once you decide that, apply Ohm's law. Hint: the transformer changes the impedance of the speaker as seen from the other side of the transformer.

RE: Cable sizing for Ceiling Speakers

As Scotty posted, the correct approach is the "70volt" systems (there are other voltage variations).

Here's a ref to get started: http://en.wikipedia.org/wiki/Constant-voltage_spea...

With such higher voltage audio distribution, the wire can be (much) smaller gauge than if you tried to use an 8-ohm speaker at the end of a very long cable.

RE: Cable sizing for Ceiling Speakers

The last ceiling speakers I worked with were 24V AC powered 4 wire, two power and two audio. Built in audio amplifier with audio isolation transformer on the input. These seemed to be hooked up with solid #20.

RE: Cable sizing for Ceiling Speakers

It'd be better to send high level audio a km, rather than low level audio to be remotely amplified at the speaker. Relative noise level, etc.

The '70volt' type standard for speakers is just audio at a much higher voltage, with transformers. Same concept as your local power grid. Voltage drop goes as the inverse square of the voltage ratio.

It's the standard approach.

RE: Cable sizing for Ceiling Speakers

From what I've read, getting high-quality audio on 70V system might be somewhat expensive

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RE: Cable sizing for Ceiling Speakers

Probably less expensive than getting high quality audio through a km of suitable cable at 8 ohms. smile

You're right. The typical little '70v' audio transformers I've seen aren't intended to pass a lot of bass. I actually have one or two fairly hefty ones in my junkbox, intended for the source end.

I had assumed that this was for paging. Or 'Muzak'.

RE: Cable sizing for Ceiling Speakers

Maybe it has a cafeteria.

RE: Cable sizing for Ceiling Speakers

(OP)
Our thermal power project is a coal based Power generation plant of 1980MW power generation capacity (3 units of 660MW each). We need speaker's as part of public address system in entire plant for making announcements like fire hazards warning, emergency evacuation of area, operational instructions and page/party announcements. Apart from this we shall have call stations at very locations for man to man calling.

RE: Cable sizing for Ceiling Speakers

Is there actually a ceiling in which to mount the speakers in every intended location?
... or are you intending to just hang them from the bar grate of the deck above?

Is there some kind of acoustic shelter surrounding the speaker locations, so people have a chance of hearing the speakers over the noise generated by the powerplant?

Do you have strobe lights near the speakers to let hearing-impaired people know that something important is going on, and they should turn on their hearing aids, or ask someone what's happening, or ... run?
... and to let normal people know that they should move closer to the speakers so they can maybe hear the speakers?


Mike Halloran
Pembroke Pines, FL, USA

RE: Cable sizing for Ceiling Speakers

(OP)
Exactly.... We are having Cone type loud speakers for open area whereas box-up ceiling speakers for closed room or area where roof/ceiling is there. Also we have flashing lights in speakers placed in noisy area. Acoustic Hoods & soundproof Booths are provided for call stations.

RE: Cable sizing for Ceiling Speakers

The acoustic quality of an outdoor horn speaker is so poor that the limitations of the line transformer won't matter.

Here's an application note from one of the better-known professional amplifier brands which might help you understand how this works: http://www.crownaudio.com/media/pdf/amps/138905-1_...

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