A:Answer Hello AlanW. The issue is that the LG CX 65 inch Class 4K Smart OLED TV w/ AI ThinQ® (64.5'' Diag), Model # OLED65CXPUA features an HDMI eARC port and you're connecting it to an HDMI ARC port. HDMI eARC is not backward compatible with HDMI ARC. If your TV is HDMI eARC enabled, but your AV amp or soundbar is only compatible with HDMI ARC, it's likely you'll get a sound - but the bandwidth restrictions of ARC will mean you won't be able to experience the high bitrate audio that eARC can provide. So no, it's not backwards-compatible...^IFV