The active control of broadband noise in duct systems has achieved enormous success in the past two decades. To alleviate the Active noise control (ANC) system for higher order duct modes requires the development of a multi-modal control system. Previously, the performance of such an ANC system has been evaluated at the error microphone position. In this paper it will be shown that the performance of such a multi-modal ANC system can be misleading if it is not measured at a set of remote (monitoring) sensor locations which are further downstream than the error sensors used by the adaptive controller. Experimentally, the performance between two control strategies, namely Independent Modal Control (IMC) and Fully Coupled Control (FCC), have been compared at both error and monitoring microphones of a circular duct setup.