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Q: What are the common ohm ratings for guitar speaker cabinets?

A: The common ohm ratings are 16, 8, and 4 ohms.  It is important to look at the cabinet inputs to correctly match the rating for your setup to ensure the optimal output and performance of your amplifier.  While some ohm mismatches are acceptable, other ohm mismatches can cause failure in your amplifier's power amp section.

REMEMBER: Resistance is measured in ohms. Resistance determines how much current will flow through a component. A very high resistance allows a small amount of current to flow (i.e. a 16 ohm speaker load draws less current than an 8 ohm amp is ready to supply, but it will work safely). A very low resistance allows a large amount of current to flow (i.e. a 4 ohm speaker load draws too much current from an 8 ohm amp, ultimately overheating the amp).

Unacceptable Ohm Mismatches:  When connecting any amplifier to an external cabinet it is important to keep in mind that the ohm load of your cabinet should not be lower in number than the ohm rating of your amplifier (which can cause the amplifier to fail). I.e. - If the amp output has an overall rating of 8 ohms DO NOT run with an external cab that has an overall rating of 4 ohms.

Acceptable Ohm Mismatches:  It is acceptable to run the overall ohm load output of an amplifier to a cabinet that is higher in number. I.e. If your amp output has an overall output rating of 8 ohms you can run into an external cabinet that has an overall rating of 16 ohms.  Be aware that you will lose ~15-20 percent of perceived volume with solid state power amplifiers when running this type of ohm mismatch, but you will suffer no failures.