Episode 030: Watts and Ohms

What do watts and ohms ratings of amps and speakers mean, and how can you match them properly?

Thanks to Chris Cox, a listener who wrote in with some questions about this topic.
What’s the ratings of your favorite, most-used amp?

  • Dave: 350W into 8ohms or 500W into 4ohms
  • Paul: 500W into 8ohms, 800W into 4ohms

What do these numbers mean?

  • Need to talk about ohm’s law
  • Need to talk about wattage

Matching cabs with an amp — do you mix and match?

  • Dave:
    • I have – can be tricky especially when going used and there isn’t much information available
    • Cheat sheet on daisy chaining: (Ohms x Ohms) / (Ohms + Ohms)
  • Paul:
    • The easy one to remember: two cabinets of the same impedance make half that impedance
    • Running two 4ohm cabinets is almost never a good idea and will roast your amp, unless specifically designed for it

Some good rules of thumb

  • Go by the manufacturers recommended ohm capabilities/limits
  • Try not to blow up your amp, especially if it’s a tube amp
    • Great point… tube amps respond way worse to this scenario than solid state
  • Speaker wattage rating — matching to amps
    • If they’re close, don’t worry about it
    • Riskier to hook up a very high wattage speaker to a low wattage amp

Photo by Fré Sonneveld on Unsplash

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