Feedback and echo with the TCC2.
Regarding feedback, the True Voicelift feature is accessible when activated on the analog output as well as on the TCC2 Dante Main Output. This signal should be utilized to send to your local ceiling speakers. Below a picture of the Dante channels TCC2 in Dante Controller.
(The FarEndOut is a mirrored signal of MainOut, with no True Voicelift algorithm applied if enabled.)
This will assist in raising the feedback threshold point compared to when it is not used. However, if the volume of the ceiling speakers is excessively high, a feedback loop may still occur and therefore careful gain staging is quite important.
For the intended design, which aims to provide additional volume for the audience at the back of the room so they can hear the presenter at the same level as those in front, it functions effectively and using it will yield improved results.
Concerning echo, this issue arises from the audio coming from the other side ("far end") being fed back into the TCC2. One solution is to route the far-end audio to the TCC2's FarEndRef input in Dante, which will direct the beam downward, thereby limiting sound pickup from the ceiling speakers whilst the far end is talking in the room. This is beneficial.
Additionally, it is crucial to establish an echo cancellation routing in your DSP to filter out the audio from the far end. Attached is a routing example demonstrating how you might implement this in QSYS (a third-party DSP).
For more information on True Voicelift, it's parameters, and effectively utilizing, please see the following document resource: