I decided to do a bit more testing today. I used three radios, a Kenwood TK-3131, a Blackbox-U, and an HYT TC-500. I also used two different headsets, the Sena SMH10/SR10 combo with both the Kenwood and Motorola twin-pin connecting cables, and a Motocomm wired headset, with adapters for both radios types. I gave a radio to my wife which she hand held in her office, while I switched between the various headsets and radios in a different part of the building.
Nothing new to report with the radio test. I found everything to work correctly when speaking directly into the radio, and when using the wired Motocomm helmet headset. However, when using the SMH10/SR10 combo, my wife could barely hear me. The volume was dramatically lower when using the Senas compared to the wired headset and the built-in radio microphone.
I took my testing one step further this time. I paired a Plantronics Voyager Pro Bluetooth headset with the SR10. I found the volume to be quite good when using the SR10 with the Plantronics instead of the SMH10. So there could be an issue with my SMH10, and not the SR10. I would like to test with a different SMH10 but I don't have one available at the moment. My riding partner has one but he's out of town for a while so I'll have to wait until he gets back.
It's a little surprising to me that the evidence now points toward an issue with the SMH10 since helmet to helmet communication with my riding partner has worked well. The audio has been loud and clear, even through earplugs.
Come to think of it, I don't think that we have used helmet to helmet intercom since I upgraded the firmware in the SMH10. Wonder if that could be part of the issue. I'll have to wait until I have another SMH10 around for testing which won't be for another week or two when my riding partner gets back from vacation.