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Amplifier Power and Speaker Power

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  • Amplifier Power and Speaker Power

    I've posted this question elsewhere, but I'm hoping people in this forum have thoughts on this. I'm a musician first, and tech second. I'm about to do some speaker swaps with the new tube amp I got for harp. I won't name the amp, because I don't want this to be a discussion about the pros and cons of various amps for harp. My question is more general:

    What is the effect of mismatching the power of an amp and the power handling capability of its speakers? Assume the impedance has been correctly matched, e.g. 8 ohms/8 ohms. But what happens when you match a 100 watt amp head with a speaker capable of handling only 30 watts? Or do the opposite, match a 30 watt amp head with a speaker capable of handling 100 watts? I'm interested in three issues for each kind of mismatch:

    Scenario 1 - Powerful amp, weak speaker(s). Anybody got on about these questions:

    a. Potential damage to the speaker(s)
    b. Potential damage to the amp
    c. Effect on the ultimate sound

    Scenario 2 - Weak amp, powerful speaker(s). Anybody got thoughts on these questions:

    d. Potential damage to speaker(s)
    e. Potential damage to the amp
    f. Effect on the ultimate sound

    Until I started looking more deeply into this issue, I thought the idea was to match, as closely as possible, the power of the amp with its speaker's power handling cabilities. Now I'm learning that's not necessarily true. Help me out!


    wolf kristiansen

  • #2
    1, A, B and C
    2, F

    Mission Amps
    Denver, CO. 80022


    • #3
      its of to run a 30 what amp through a 100 watt speaker/s other way around is a bit risky. A lot of older speakers could actually handle more than they were said to so running a 30 watt amp through an older 20-25 watt speaker can sometimes be ok, but not always. For instance i sometimes run a crate stealth (50 watts) into a 10" that can handle 30 or 40 watts (i cant exactly remember) with a crossover to a 4 watt tweeter and it hasent crapped out yet.

      But it can then have the risk of rooting the speaker and if there is no load on the amp it can go on to fry the amp.

      When it comes to sound everything is going to affect the sound. whether that is in a good way or a bad way is different.

      And the impedance doesnt always have to be correct you can sometimes safetly run a 8 ohm amp into a 16ohm speaker, its less risky than heading in the other direction.


      • #4
        It's not that older speakers could handle more, they really can't. It's more that many modern amps aren't measured in true RMS...I've seen PMPO (peak music power out), peak power, and AES, whatever that might stand for (maybe Another Esoteric Statistic). I was recently given a 200 "watt" power amp that maybe makes 100 watts bridged into the right load for less than say 50 microseconds.

        I swap out my harp speakers pretty frequently for different gigs, so there is something to different speakers. Underrated speakers will rip themselves apart (nothing like a 25w speaker and a ~50-60w sylvania 6ca7 push-pull amp in near class B...literally ripped the cone out haha). Or they go open, and the OPT blows...nasty.

        When I am jamming in a small space with a quiet drummer, I'll use a 50w ceramic CTS's not very efficient, so I get good overdrive at a lower volume. It has good bass at low volumes too. When it's a really loud gig, but I'm still using my 12w EL84 amp, I use a real 1961 Jensen P12Q (fancy gold basket too, thank you moto ). It doesn't pump as much bass, but it is LOUD and can cut through anything. I had a higher efficiency Utah ceramic (I guess those are rare, they mostly made alnicos) 4-ohm speaker that really sounds nasty good sometimes too.

        I think speakers are a really fun part of working with tube amps, since they literally interact with the power tubes so much (as compared to solid state). I think I have used something like 8 or 9 different speakers in my amp. Yardsales & freepiles make it cheap too