I purchased a IMC HS-H40 helmetless headset from Whitehorse Gear to use with my Hannigan sidecar. I have wired in the factory harness from Harley, but the headset mic sounds like you are a hundred miles away and very tinney sounding. I spoke with a local radio shop (aircraft stuff) and they need to know the specs of the HD system. Any answers there. Also any suggestions. The ear side works great. The wife can hear everything fine, she just can't talk (that is not always bad, but in this case it is). I have tried the set on the riders connection with the same results. If she uses her helmet set, it works fine, so I don't think it's the wiring. She cannot wear the helmet with the top on the sidecar (too tall), hence the need for the other headset. Whitehorse is at a loss aout the system. They sent another set, same result. The bike is a 2002 Ultra.
Thanks, I like the site and the abundance of info and opinions.

 

The Harley radio/intercom is not compatible with other brands of headsets, the impedance is different from one manufacture to the other. You have to have two of the same models from anyone for it to work correctly. You will constantly be readjusting the volume to hear her and then she will think your screaming when you talk back when using opposing brands. J&M Corp is the only manufacture I know of that has a compatible microphone and you do have to order the right model at that, their products work very well with the Harley system but they do not yet have a helmetless model.
I had the same issue you did (except no sidecar ), the work around was to wear a half helmet with the same brand headset like yours for it to work correctly.