Connecting an amplifier head to a cab, or speaker cabinet, is a simple process. However, there are factors to take into consideration so that you don't damage your amp. Most importantly, always use a speaker cable when connecting an amp head to a speaker cabinet. Although it looks similar to a speaker cable, an instrument cable can cause damage to your amp head.
Plug one end of a speaker cable into the output jack of your amp head. If the outputs of your amp head have different impedance, choose the one that matches your speaker cabinet. For instance, if your cabinet is rated at 8 ohms, plug the cable into the eight-ohm output of your amp head.
Plug the other end of the speaker cable into the input jack of your speaker cabinet. If using multiple speaker cabinets, plug another speaker cable into the output jack of your speaker cabinet. Then plug the other end of the speaker cable into the input jack of another speaker cabinet. Connecting speaker cabinets in this way is called wiring in parallel. When you combine two speaker cabinets rated at the same impedance in parallel, the impedance drops in half. For instance, if using two eight-ohm speaker cabinets wired in parallel, the total impedance becomes four ohms. Fewer ohms mean less resistance.
Make sure the speaker cabinet can handle the power of your amp head. If your speaker cabinet can handle 200 watts at eight ohms, make sure that your amplifier does not output more than 200 watts at eight ohms.
Never plug an amp head into a cabinet rated at lower impedance than the output of the amp head. Doing so could damage the amplifier.