A:Answer Hi neecy, we appreciate your interest in our product. You need 2 SRSXB32 speakers to use the Speaker Add function of this unit. Moreover, this unit also has a Wireless Party Chain function if you want to have a party with loud volume. You can connect multiple devices (up to 100 devices). Compatible devices: SRS-XB22, SRS-XB32, SRS-XB21, SRS-XB31, SRS-XB41, SRS-XB20, SRS-XB30, SRS-XB40, GTK-XB60, GTK-XB90. You can also operate the Wireless Party Chain function on “Sony | Music Center.” Thank you. ~Earl