Loudspeaker Cables and Connectors   

The loudspeakers must be connected with speaker-grade wire to the outputs of the the amplifier.
The type of connector to the speaker can vary widely among models with bannana, phone, friction, screw, and XLR being in common use.
Make sure to observe polarity of the wiring when making connections between loudspeakers and amplifiers. 
This means ensuring that for each channel of the amplifier the positive terminal is connected to the positive terminal of the loudspeaker, and similarly for the common terminals. 
When the two loudspeakers are wired differently or reversed the resulting sound can be degraded at playback due to phase cancellation.