Can't get my TV listening device to work

menu option--T-coil
what it does--reduce noise on hearing aids equipped with a telecoil (T_Coil) feature.It shortens talk time, so keep the battery fully charged
exert page 10 user manual

I'm not sure you can with roku

The Sennheiser Set 820S is a TV/music listening system specially designed for hearing aid wearers. With roughly a 100 foot range, Set 820S users can leave the room while still being able to listen to a TV program or music. Enhanced with radio frequency (RF) technology for a larger coverage area, users won't need to worry about missing a word of the program or song. The Set 820S consists of the 820 RF stereo transmitter and 820-S RF stereo bodypack receiver. The transmitter connects to a TV set or hi-fi system; the receiver can be clipped to clothing. The receiver can be coupled with an induction neckloop (sold separately) (hearing aid must have a t-coil), direct audio connection (to cochlear implants or BTE hearing aid) or Sennheiser headphones with a 3.5mm jack. Two year warranty. · Bodypack receiver · RF wireless transmission · Stereo or mono operation · Quick charge feature · High SPL (125dB) · Approximately 100 foot range · Maximum volume and bass response adjustable by hearing professional

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wireless speakers are also available ........ but you may not hear 100% of sound............. click above shown link.... you will find many similar products ...... you can check thier price , features, etc & then you can finalise the one that suits you best ..............

you need to replace the voice coil. it is already grounded, that is the one inside the mic ball (where you speak or sing). it is not repairable so you need to purchase a new voice coil