Wiring a stereo player into a megaphone

[AquaHydroChem]

Hi there

I recently purchased this item off ebay http://www.ebay.co.uk/itm/152003289577?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
I wish to wire it up to the jack plug out of a stereo player like my laptop
As you can see from the link there are 3 wires; red, black, yellow. (not the red and black 12v power wires)
I have taken the casing apart at the speaker and the 3 wires go into a circuit board, and I am unable to work out which wire dose what
Any help please in telling me which wire dose what?

 

[DaveHerns]

Is it actually a loudhailer with an audio input or just a 5 sound siren ? Very much doubt it can do 300dB !

 

[Sam Gangee]

It's a siren. I'm a qualified electronics engineer but even I couldn't convert it without a circuit diagram. Forget it and buy a proper amplifier and speaker system.

 

[AquaHydroChem]

It's a siren. I'm a qualified electronics engineer but even I couldn't convert it without a circuit diagram. Forget it and buy a proper amplifier and speaker system.

This any good?

 

[Sam Gangee]

It looks like yellow is the feed from the volume control. Do you hear a click or buzz when you touch it with your finger (volume turned up)?

 

[AquaHydroChem]

Sam
It is hard to tell, but I would say it dose crackle when I wiggle the yellow wire; So yes it dose.

So if we now know that the next question is which is live and earth?
Or should we just presume red is live and black is earth?

Thanks
AHC

 

[Sam Gangee]

By convention, red is positive and black is negative. Your images suggest that might be so but the simplest way to check is with a multimeter set to volts.
http://www.amazon.co.uk/dp/B00QGQOT0Y

 

[Gerrydelasel]

I would guess the red is the +12V to the controller. Yellow will be the audio (siren) signal, and black is ground. If this is correct then you won't need the red anymore. Connect the yellow and black to your audio source.

 

[AquaHydroChem]

I bough a set of cheap head phones today and cut the end off of one of them
I have wired the speaker plug up to my mega phone as described above (red positive, black earth)
And plugged the jack plug into my laptop and played some music and switched the mega phone on.
There is very very little sound coming from the mega phone, you have to put your ear next to it to hear anything (and yes my sound card on my laptop plays fine)
So it obviously works but the question is why is it so quiet?


And finally I have to ask what happens if you reverse polarization on an audio system?

 

[Sam Gangee]

I have wired the speaker plug up to my mega phone as described above (red positive, black earth)...
So it obviously works but the question is why is it so quiet?

It needs a microphone not a speaker and the microphone needs to have the correct impedance and output level. Try an electret microphone. In addition, the yellow wire needs to be disconnected from the existing circuit.

And finally I have to ask what happens if you reverse polarization on an audio system?

The red & black? Smoke.

 

[Gerrydelasel]

I have wired the speaker plug up to my mega phone as described above (red positive, black earth)

Use YELLOW and black

 

[AquaHydroChem]

I have just disconnected the yellow volume wire and nothing has happened.
I have just connected the yellow wire into the earth or black terminal as instructed to do so by Gerry and all I got was a load of noise from the speaker and smoke from the microphone

 

[Sam Gangee]

As we are all trying to explain, yellow is your audio input. Black is zero volt or ground.

 

[Gerrydelasel]

*bangs head against wall*

 

[AquaHydroChem]

*bangs head against wall*

I am that I really am that!

Use YELLOW and black

If that is what you said then that is what you said Sir; How am I supposed to interpret your mind over ciberspace.
If there where a red wire not in use then they would not of spent the money putting it there in the first place would they not?