Amp output/ohm/speaker

K, so according to the Fender site my amp is 60watt output into 4 or 8 ohms (switchable) into 4 30watt speakers.

This means what?

What would switching from 4 to 8 ohms do?

I do not know what its set at right now.

If I were to change speakers and got either lower or higher wattage speakers, what would be the result?

Ok, you can get a primer on calculating load impedance >here<.

An adjustable output allows you to match the output to the load impedance for the most efficient power transfer. A mismatch will reduce the transfer efficiency, and the losses show up as excess voltage or current (and heat!) in the o/p transformer.

Your four speakers are probably 8 Ohms each, connected in series-parallel to give a net impedance of 8 Ohms. (Did you read that thread I linked to?) Setting the output for 8 Ohms will match the load nicely to your output tubes.

If you connect an additional 8 Ohm speaker cab, it will be parallel to the original speakers, giving a net impedance of 4 Ohms. So you need to set the output selector to 4.

Your amp puts out 60 Watts. No matter what speakers you connect, the amp only has 60 Watts to deliver. That power will be split up among the speakers according to their impedance. That gets a bit complicated in multi-speaker setups. Equal impedances will share the available power equally. So your original speakers will get half of the power, and the 8 Ohm extension cab gets the other half. If the extension cab has two speakers in it, each one gets half of the total power taken by that cab. In your case, that would be about 15 Watts each. Half of 60 Watts to the cab; half of that to each of the two speakers. The four original speakers would each get 1/4 of the 30 Watts sent their way, or about 7 1/2 Watts each.

Amps are rated for the clean power they produce. Pushing into distortion can get you up into much higher numbers. You should always use speakers rated to handle at least 50% more power than they are likely to see. Your four stock speakers are probably rated at 25 Watts each. If you use a two-speaker extension cab, they should also have at least 25 Watt rating. If you use a four-speaker extension cab, you could get away with using 15 Watt speakers, provided you never use it without also connecting your original speakers as well. For a cab that will be expected to handle the entire output of your amp, you will need to select speakers that are rated for a total of at least 100 Watts.

Thanks. EH!