No Sound From External Speaker

[LostAgain]

Hello All,

I recently purchased a 3 watt external speaker to plug into an AMPS Rugged RAM mount for using with a 276CX and Montana 610 but can't seem to get it working at all.
Regardless of settings or volume slider locations on both devices the only way I can get any sound out of either device is to use their internal speakers.

The speaker has a 3.5mm mono plug for plugging into the speaker plug on the AMPS wiring harness.
The speaker seems to work ok when I plug it into the headphone plug on my phone.
I tried 2 different AMPS mounts, same result, no sound through external speaker.

Are the AMPS mounts plug and play or am I missing something obvious?

Thanks

Spoiler

garmin-amps-rugged-mount.jpg

[GPSrChive]

Does the speaker work if you connect directly to back of Montana 610?

[LostAgain]

Thanks, I never thought of trying that.

Yes it does work when plugged into the 610, very quietly though, can hardly hear it even with full volume on both the speaker and 610.
Speaker is two and a quarter inch diameter, 8 ohm, 3 watt max with 4 metres of 2 mm cable that ends with a 3.5 mm mono plug.
Can hear the tones better through headphones plugged into the 610, though still nowhere near as loud as I believe it should be.
The speaker mount I have for the Montana 700 is very loud at full volume, almost to the point it's painful with tone 8 on a proximity alarm.

[GPSrChive]

Please test again with a 'Stereo' audio cable.

[LostAgain]

I have, made no difference.
The speaker comes with a hardwired mono plug, I tried a stereo to mono 3.5 mm adapter and it's still almost impossible to hear it at full volume.

[GPSrChive]

I'm looking for published specs. Perhaps the headphone jack in the mount harness is intended for use with amplified speakers.

[GPSrChive]

Maybe test with standard headphones both at the back of the 610 and the mount harness.

[LostAgain]

The headphones work from the 610 and also work via the harness with the 276 in it, quite a bit louder through the powered harness than from the back of the 610.

The headphones input impedance is 32 ohm while the speaker's is only 8 ohm, but I don't believe that should matter these days so long as it's 4 ohm or above.

I couldn't find any specs either, probably a secret, only info I could find was how to wire all the data wires and to 'plug in external device to the 3.5mm output if required'