Libratone Loop is equipped with an analog 3.5" AUX minijack input which allows for a wired connection to your TV.
Use the "Headset Out" connector on your TV and connect a shielded minijack-to-minijack cable to the AUX audio input on your Loop.
This configuration allows you to use the TV remote to control the volume level on your Loop.
However, if your TV remote is not controlling "Headset Out", you can also use the free Libratone app available in Apple's App Store. A volume slider will show up in Libratone App is the speaker is connected by cable.
If you start streaming AirPlay to your Loop the sound source will automatically switch from your TV to AirPlay streaming, as AirPlay is prioritized.