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James299
August 1st, 2010, 07:56 PM
I'm looking at an amp head and it has one speaker out jack to connect to a speaker cab. It says it's rated at 4 ohms minimum. Does that mean I could still plug in a 16 ohm cab? Would that ruin anything or just lower the power output?
LeadedEL84
August 1st, 2010, 09:22 PM
You are correct. You can run a speaker cab with higher OHM rating than the Heads output is designed for without hurting anything on some amps. It will lower the output volume. Some amps sound much different with a mismatch as well.Running a cab that has different rating can in some cases hurt the amp. Especially if you are driving it hard. Some amps can handle the mismatch while others might overheat or prematurely wear out your power tubes. With most amps it is best to match the rated output to get the best sound and feel (IMO). I'm sure there are exceptions.
I'm not sure of the effect it has on a solid state amp as to how sensitive they are to running a cab/speaker with lower ohms rating. As far as damage is concerned any way. I know most SS amps I have heard running mismatched have sounded really bad.
I'm sure others will be along with a more technical explaination. I will leave that to those that know more about the science of it than I do.
tunghaichuan
August 2nd, 2010, 07:32 AM
I'm looking at an amp head and it has one speaker out jack to connect to a speaker cab. It says it's rated at 4 ohms minimum. Does that mean I could still plug in a 16 ohm cab? Would that ruin anything or just lower the power output?

Is your amp solid state or tube?

If your amp is solid state it is okay to connect it to a 16 ohm cab. A 4 ohm cabinet gets you the most power out. Running a 16 ohm cabinet will limit the power out.

If your amp is a tube amp, it is not safe to mismatch up from 4 ohms to 16 ohms. You run the risk of flyback voltage, which would destroy your output transformer. Some amps, like Fender, it is okay to mismatch by 50%. Others, like Marshall, you have to match the impedances. Marshalls are known for blowing OTs when mismatched.

There is more information here:

http://www.geofex.com/tubeampfaq/taffram.htm