Abstract: A multi-channel audio rendering system comprises an audio renderer (113) which generates audio signals for a plurality of audio channels. A plurality of interchangeable speaker units (101-109) comprises a battery (205) and an audio transducer (207) for rendering an audio signal. A charging unit (115) is associated with a specific audio channel and comprises a charging source which can charge the battery of an attached speaker unit (101-109). A linking circuit (305) can link the speaker unit (101-109) to the first audio channel when it is attached to the charging unit (115). The system can permanently associate specific channels with charging units (or passive speaker bases that cannot charge) and interchangeable speaker units (101-109) can adapt depending on their attachment. The approach may allow a charging of a (possibly wireless) speaker unit (101-109) to be achieved simply by swapping this speaker unit (101-109) with one attached to a charging unit (115).