MBevans posted, at least in part: Ever since with or without earplugs they are tinny in sound and bug me after a short time.
Custom-molded
FUZE earplugs work very well for me, and they're
cheap inexpensive. Because they're custom-molded, they fit within the "cup" of my ear and don't protrude enough to touch the factory Sena speakers.
But I also had the same shitty sound issue on my 20S until recently. I wanted to listen to podcasts stored my iPad while keeping the phone synced for making/taking calls. Decided to re-read the manual and pair my devices correctly.
There are two flavors of Sena-supported Bluetooth:
1. HFP (Hands-Free Protocol) is low-fidelity and, I swear, monaural
2. A2DP (Advanced Audio Distribution Protocol) is hi-fi stereo and sounds
really good.
Make SURE your music source is on the A2DP channel; for me, that meant blowing everything up, and re-setting the Sena to factory defaults. I also made sure the iPhone and iPad had forgotten the Sena. That way, I was confident no pairing parameters were stored in any of the devices.
Not sure how to guarantee the connection is A2DP, but assumed that the A2DP device would be paired first and that was the iPad. Sound quality was superb, and with the earplugs, I could hear comfortably at half-volume. Paired the iPhone second, and it sounds fine, too.
Hope this is helpful ...