A speaker box includes a case includes an upper side and a lower side opposite to the upper side, an electroacoustic transducer received in the case and including a first pole plate with a plurality of first gaps for communicating with the magnetic gap, a second pole plate attached on a lower surface of the first pole plate. The second pole plate defines a second main member, a plurality of second auxiliary members extending from a periphery of the first main member, and a plurality of second gaps corresponding to the first gaps. Each of the second auxiliary members defines a longer auxiliary member and a shorter auxiliary member respectively.