The point is that we have to acknowledge that we all have different aircraft and headset and it's all about common sense and not monkey business. I'm aware of the FCOM setting of 1 o clock position for the loudspeaker. On the ACP, I usually keep the knob at 12 o clock position depending of the aircraft as in reality it varies from aircraft to aircraft. If you do have interference, set the loudspeaker to a lower setting. We personally put it to a minimum setting as we don't rely on loudspeakers when using headset. If you are lucky and don't experience any interference, then use them as your discretion. Simple as that. Communication should be as clear as possible to guaranty the best outcome.