A conference call system comprises an input interface for receiving during a conference call at least two input streams of audio signal, each from another source. A selection unit is connected to the input interface, for selecting a number of dominant speaker streams out of the input streams, the number being less than or equal to a maximum number of dominant speakers value and each of the dominant speaker streams representing speech from a respective dominant speaker. A mixer is connected to the selection unit, for mixing the selected streams into an output stream. The conference call system comprises an output interface for outputting the output stream and a selection control unit connected to the selection unit and the input interface, for dynamically setting, during the conference call, the maximum number of dominant speakers value based on dynamics of the conference call.