What Output Impedance Means And What To Look For

When using any guitar amp head it’s important to make sure that the impedance matches the impedance of the speaker you’re using. Most modern amplifier heads are built so that they can send out the correct output impedance but there are still cases where you can blow your speakers or the amp.
Although it’s always best to use the amp head/cabinet combination that your amp head manufacturer recommends, there are times where you’ll need to know if you need to worry, or if you’ll probably be fine. Even if you are assured that your amp/cabinet combination works together, there will be times when you try to use your amp head with different sets of speakers.
Without getting too much into the science behind it, there are a couple basic rules to remember to know that your combination is safe and going to work.


  1. The best possible scenario is where the speakers you are using match your amp.

    Amp heads commonly have output settings of 4, 8, or 16 Ohms. The best example would be to connect a 16 Ohm amp head to 16 Ohm speaker if possible. If you have 8 Ohm speakers, use the 8 Om output on your amp head. etc.

  2. Never use an amp head that has a higher rating than the speaker.

    Think about this as the speaker needing to be at least as powerful as the amp head. If the amp is too powerful, the speakers could blow when they try to play the sound. This is why it is also important not to play through your amp head without any cabinet attached. All that power has no where to go and it could blow the amp head.

In summary:

  • It’s good when the output impedance of your amp matches your speakers.
  • It’s ok if the speakers are higher impedance rating.
  • It’s bad if the speakers are too low of an impedance rating! This could blow your amp.

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