The back panel of each of your speakers contains a large opening called a “bass-reflex port.” A bass-reflex port enables the speaker to get and push air and increases the efficiency of the system at low frequencies. In the Ceres, the port faces the rear, so it’s a “rear-firing” port.
The bass-reflex port is not to be used as a handle to carry your speaker—nor should it be be blocked, or it will affect the quality of your sound and may damage the speakers.