question about amp wattage to speaker wattage

Discussion in 'Amps and Cabs' started by joemail75, Feb 5, 2012.

  1. joemail75

    joemail75 Member

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    is running a 20 watt amp into a single 25 watt speaker bad for either? im thinking of buying a greenback but have read that you should get a speaker that can handle at least twice the load of the amp. i dont mind if the speaker will break up early i just dont want to blow anything up. thanks!
     
  2. mcdes

    mcdes Member of no importance

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    depends how you play the amps?

    do you use it for dirt, and dime it? or do you use it clean and use pedals? to dime it would really push a speaker.
     
  3. wolfman63

    wolfman63 Member

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    Depends on how loud you play and for how long. I've heard the "rules of thumb" and ignored them all. I have a couple of Celestion Blues that have been powered by everything from five watts to a hundred. And they are rated at fifteen watts. So either I'm right or just damned lucky. I won't say you can't blow a low wattage speaker but it's harder than one might think. The only speakers I've ever blown were cheap speakers. The Blues are really efficient, so I guess they don't take as much power to make them loud enough. The older they get the less efficient they become due to the alnico magnets loosing strength, and the surrounds breaking in, and the better they sound.
     
  4. joemail75

    joemail75 Member

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    i dont plan on maxing the amp out but i do want to drive it a bit.
     
  5. norumba

    norumba Member

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    not meaning to hijack this thread, but its a variation on the same question...so maybe folks can talk in general as well.

    I have a similar situation -- i have a cab with two vintage Eminences; Eminence answered an email and told me they were 1970, 8 ohm 2" voice coil and a 20oz Alnico magnet, but couldnt offer a power rating.

    I have a line on a similar pair from 1974 up on CL; owner says they were pulled from an older Peavey, 25 watts each, 8 ohms, 1.5 voice coil, but neither he nor Eminence can tell me the mag. weight.

    The 1970 set i 'm running through a SF Bassman 50 head, no problem. I plan to use the other pair for my SF Bassman 70 head, but a little bit worried about the juice factor. I run both amps in stereo , not loud but really clean; I'm running the Bassman 70 with jumpered channels, and channel volumes and master all about 5 or less (sometimes I'll vary that ratio, but total is alll in that range) .

    (Now that said, the 70 seems to have less power and oomph than the 50, so im taking it in to get another look at. Running the 50s volumes at about 3 or 4, and that balances volume -wise with the 70)

    Any thoughts on what set might hold up better for the 70?


     
  6. mcdes

    mcdes Member of no importance

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    then i reckon youll be fine
     
  7. dunara

    dunara Member

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    Another couple of things to consider:
    a) Boost - are you planning to use any kind of lead boost? That can greatly increase the speaker loading over and above the amp's wattage. Some others here may well have figures for this, but any kind of boost pedal - I use an MXR micro amp or an original Marshall Guv'ner - that makes a solo leap out of a busy arrangement in a live setting, must present a challenge for speakers.

    b) Speaker type. Some speakers seem to be able to handle more than their manufacturer-rated wattage comfortably. A dimed Vox AC30 may well be putting out 40+ watts, if you use a loud guitar (say, a Les Paul) and boost the input; yet the two Celestion blue speakers - rated at 15 watts each - don't complain. Sound fantastic, actually. JBL speakers have a similar reputation for ruggedness. However; the original speakers (Jensens?) in silverface Twin Reverbs were notorious for blowing when you dimed the amp. The 'twice' the output wattage' rule is essential for bass players, but guitarists can afford to 'sail a bit closer to the wind', provided they're using proven, quality speakers.
     
  8. FFTT

    FFTT Member

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    Well I love my old '73 CTS AlNiCo's but you do have to keep age in mind.

    Normally with many AlNiCo's, it's a good idea to match the amp output fairly close
    to the speaker ratings. Higher powered AlNiCo's may loaf a bit producing
    a loose muddy low end and the top end won't compress as it should.

    The Fane AXA12 is the one exception I've found because their low end
    stays tight even with 30 watts into a 100 watt rated driver.

    If you go to Webers, the lower the power rating, the higher the efficiency.

    So their 100 watt AlNiCos are less efficient than their 15 watt Blue.
     
  9. GCDEF

    GCDEF Supporting Member

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    It really can't. A boost pedal doesn't add wattage to an amp. Once the max power is reached, it'll just distort and compress more.

    Greenbacks are pretty robust. You should be okay. What amp is it?
     
  10. Onioner

    Onioner Member

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    It just comes down to risk. Double the wattage and there's no way you'll blow a speaker. As you creep on down, the likelyhood increases. How low can you reasonably go? That depends on the speaker and the amp. There are certainly folks out there driving 15W speakers with 15W amps, and only occasionally does a speaker blow. Just comes down to how far you're willing to push it.

    My rule is "double the wattage, then shave some off." I'm absolutely find powering a 30W cab w/ an 18W amp. I'll run a 25W amp through the same amp, but won't crank it. Sadly, I don't think there's a hard and fast rule for how much power handling you really need.

    For some reason, I thought it was the opposite for Webers. The higher the power rating, the more efficient. I thought it was 'bigger magnet = more efficient,' at least as a general rule.
     
  11. joemail75

    joemail75 Member

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    i'll be playing a dr z remedy. 40 watts but i usually half power it to 20w. Its SO loud and the speakers im playing through right now are very efficient so im trying to get something that will allow it to break up quicker at lower volumes. I still dont expect to dime it out. just running it past 9 oclock would be nice! im thinking of one greenback because they are rated about 5db less than my current speakers.
     

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