Radio in wiring clarification - Whelen

[militarymedic23]

Would like to ask for some clarification on what exactly is happening with the two Radio In wires for radio rebroadcast.
All the manuals/install guides point to the two wires going to a speaker, but I'm interested in using this from a 3.5mm stereo jack output.
I did find a post about someone asking about a similar concept, using an iphone or other media device and converting stereo to mono, but I'm still not seeing what exactly is going on with both wires.
A mono connection would have audio on one strand of wire and ground on the other. So for the whelen wiring harness, is this what they are aiming at, but it doesn't matter if ground is attached to one blue wire or the other? If so, would this be as simple as chopping a mono extension cable, split/separate the two strands and splice them to the blue Radio in wires? Plug in whichever audio device I choose and I'm set?

 

[MtnMan]

If so, would this be as simple as chopping a mono extension cable, split/separate the two strands and splice them to the blue Radio in wires? Plug in whichever audio device I choose and I'm set?

Yes, it's that simple. The two wires go to an isolation transformer, so it doesn't matter which is which.

 

[militarymedic23]

very cool, thanks!

Are there any words of wisdom regarding dos or don'ts in terms of piping audio from an external media device (iphone/ipod) such as volume or type of audio that may not come across too well?

 

[MtnMan]

It depends on the anticipated use. The PA/rebroadcast functions are intended for intermittent, "voice quality" use. Fidelity isn't great and and some manfs caution against prolonged operation (e.g., playing music). So, not the best setup for a mobile DJ operation.

 

[militarymedic23]

Ah I see what you mean. I wasn't intending a DJ service with it, but more of intermittent audio bits, more voice based that music.

Will give it a try and see how it goes!

 

[militarymedic23]

one more question on this.
Most devices now are stereo output, but the technicalities of combining stereo to mono are... interesting. Most of the forums direct the use of 1k resistors so the two audio channels aren't delivering too much output to the end device when combined. They say this isn't terribly important for things like headphones but more important when it comes to amps. I'm wondering on that point since the siren unit is an amp in some sense given the power increase to the speakers.

Any comments on how this has been or may be tackled?

 

[MtnMan]

Yes, you can use resistors to combine the channels. About 150 Ohms would be best.

 

[PablovskyGTL]

Hello, were you able to make progress with your idea?