Where can I obtain the speaker for a helmet, I refuse to use in-ear 'phones.
I concur, earphones are a PITA.
I've installed a couple
of these (45mm version) in my Arai along with a lead and 3.5mm jack-plug. It's a neat job, if I say so myself, speakers are behind the lining and all wiring is hidden except for where it comes out on the right, near the strap. I recessed the speakers slightly by cutting a penny sized, 5mm deep hole in the polystyrene inner (on the Arai this is part of the cheek-piece) and hot-melt glued the matching rear of the speaker in. Ear clearance is ample, even with my big ears.
I run the lead down inside my collar and out at the waist where I plug it into a curly extension lead attached to my tank bag. I think running down your arm and out at the wrist might be asking for trouble. With my set-up I can dismount and then unplug and as the connectors are straight will detach on their own if I forget, or heaven forbid, have an off.
I can hear the audio instructions clearly up to about 70-80mph with Max-Lite earplugs and can still hear something above that but might have to glance at the screen to confirm. Audible volume is obviously dependant on the output of your GPSR, speaker placement, ear plug type, wind noise (some bikes worse, some better in this respect) and how deaf you already are
Audio quality isn't great, tried plugging in my MP3 player just to see and it wasn't exactly HiFi... my setup is mono anyway but the range of the speakers just wasn't up to it (what do you expect for £2.26

) However, for GPS audio it's fine and, personally, I don't want music or phone whilst riding anyway.