Yes, but be careful or you will introduce an operational issue. Inserting the control will reduce volume to the speaker at least slightly. This might result in that speaker not being loud enough while the speaker without a control being too loud. Many of the controls that you’ll find are designed to be used in situations where you want to add more speakers than the amplifier will safely support. These are often called “impedance matching” controls. These controls will have a setting used to reduce the power to each speaker, such that the total load of all speakers is safe for the amplifier. When using a single such control in you case, set it for “1x“. This will minimize the insertion loss for your speaker.

Normally, these controls are inserted into all speakers connected to an amplifier — allowing each room to be set to a custom level.