Ar.Pi

Hi all, So I hooked 4 Cube cameras (DS-2CD2432F-IW) to my NVR and I can only listen (mic) to the camera but not talk (speaker). Cameras 2-way audio works fine if connected directly to router. I enabled the Video & Audio output in Configuration and did everything I could think of. I've researched and apperantely you cannot pass through Speaker audio with the NVR and I called Hikvision and was told I will need an External Mic/Speaker (Louroe makes them?) to connect to my NVR and pass through POE the 2-way audio. Can someone please explain if and what I need to purchase and how to connect it in order so I can speak through the cameras that are connected to my NVR? Much appreciated!