Listen Technologies LA-164 Ear Speaker

The LA-164 hooks over one ear on a plastic clip rather than sitting in the canal, so it does not flatten hair and it can be handed to a new user without a sanitary cover. Output is strong enough to work in a live room.

It runs 20 Hz to 20 kHz into 32 ohms with 115 dB sensitivity, on a 3.5 mm stereo plug and a 36 inch cord. That cord is the receiver's antenna, so it cannot be shortened or swapped for a generic lead.