An optional accessory available for the QB4 and the BirdXPeller PRO bird repellers are Remote Extension Speakers, Please note that these are the same speakers that are included with Super BirdXPeller PRO Critter Blaster PRO BroadBand PRO and BillBoard PRO, You should not need replacement of the speakers on any of these bird repellers but if needed of course replacement can be ordered, For the QB4 ultrasonic bird repeller custom configurations or areas divided by walls use up to four remote speakers to stretch sound farther, SKU: BRX019