When connected via COAX OUT or OPTICAL port to an external amplifier, the output signal level is fixed.
With this connection, both built-in and external speakers will output audio.
You need to adjust volume on IFP speaker via IFP volume control button or remote control and adjust volume on external speaker by amplifier.
2. AUDIO OUT:
When connected via AUDIO OUT port to external amplifier/speakers, the built-in speaker will be muted. Please adjust volume on IFP volume control button, remote control or on amplifier/external speakers.