Wattage = Volume??

Discussion in 'Amps and Cabs' started by 3m3r5, Jan 8, 2008.


  1. 3m3r5

    3m3r5 Member

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    Could somone please explain in lay terms how watts actually relate to volume or is it just a common misconception? I was jammin' with my bass player the other weekend, testing out my recently acquired Princeton Reverb and he was going through a 200 watt SS Torque amp, we both cranked the volume up full and my little PR was still slightly louder!! And how come Hifi amps that claim to be 100 watts or whatever are never as loud as guitar amps?? Is it simply to do with solid state wattage being less dB than tube wattage? If so why?Thanks.
     
  2. SuperStrat

    SuperStrat Member

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    Perceived volume is frequency dependent. It takes more power to make the low frequency bass notes loud...
     
  3. John Phillips

    John Phillips Member

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    Volume = clean power x peak power x distortion x speaker efficiency x number of speakers / frequency response.

    (Non-mathematically, anyway :).)

    It's nothing inherently to do with the difference between tube and solid-state - the actual measured clean power output is exactly the same for both.

    But the final volume is affected by so many other factors that the plain 'wattage' is almost meaningless unless you're comparing very similar amps.

    Since hi-fi amps are never designed to be driven into distortion, they don't come anywhere near to producing the same peak power, and they have to do it evenly over the whole audio frequency range - guitar amps operate over a much narrower bandwidth, aren't concerned with 'controlled' evenness, and are intended to distort, so the actual power available can be several times as much in the midrange, where both the speakers and your ears are most sensitive. Guitar speakers are far more efficient than hi-fi - more than 10dB in many cases, which is the same as using ten times the amp power.

    Even bass amps require much more clean headroom at lower frequencies, so you need much power to compete even if the guitar amp isn't distorting - and if it is, that can produce up to double the power.

    Many solid-state amps are purposely designed not to distort in the power stage too (even if the preamp does) because it's potentially damaging to both the amp and the speakers - unlike tube amp distortion, because tube amps have an output transformer which prevents the worst frequencies getting through.

    A solid-state bass amp through a small cabinet typically needs to be about five to ten times the power of a fully-cranked tube guitar amp to compete in volume if you don't want the bass to distort, and even then it might not sound as loud just because the guitar amp will be so much more midrangy and 'present' (loud in the frequencies the ear is most sensitive to). And a Torque is not exactly the most dynamic 200W amp you're likely to find - largely a function of the quality of the power supply.
     
  4. clothwiring

    clothwiring Supporting Member

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    Maybe we should measure amps at what SPLs they can achieve? When I got the /13 SJT 10/20...it was WICKED loud. Louder than my Marshall Jubilee 100 watt head.
     
  5. Roobubba

    Roobubba Member

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    but then you need to also take into account the speakers being used, the cab, etc etc etc. Comparing things is best done in the shop, in person, with as much of your own equipment as possible.

    Roo
     
  6. mlynn02

    mlynn02 Member

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    how about this circumstance?...

    will a 100 watt marshall super lead be appreciably louder than a 50 watt super lead if they are going through the same cab, say with greenbacks?
     
  7. sixtonoize

    sixtonoize Member

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    It won't be much louder. It will have a different tonal response, though, because the 100 watt amp will have an easier time reproducing the lower frequencies. 100 watt amps tend to sound "deeper".
     
  8. studiodunn

    studiodunn Member

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  9. B_of_H

    B_of_H Member

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    the low end seems to certainly make a difference but also speaker effeciency. I have a Emi Wizard and that thing makes even a 15 watt amp loud as hell with just 1x12. While other speakers seem to tame a lot of volume off the same 15 watt amp.
     
  10. Franktone

    Franktone Member

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    A 100W Marshall is definitely a lot louder than a 50W Marshall, especially 2-4x12 cabinets. It shakes your body twice as hard, shakes your hair twice as hard, and puts at least twice the power per square inch onto your ear drums. I am betting that the 100W Marshall is doing twice the damage to your ears than the 50W. A Marshall 100W into 8x12 really shines in terms of power in an outdoor situation when a Marshall 50W is barely coping, especially if the PA is not good to mike everybody in the band. The ear responds logarithymically to sound. In other words your ears need an exponential increase in power in order to realize a linear increase in perceived volume. To double the volume of a 1W amp you need to go to 10W. To double the volume of a 10W amp, you need to go to a 100W amp and so forth. You need 1000W to go 3 times as loud as a 10 W amp. It is easy to see this by using base 10 with exponents.
     
  11. Ricker

    Ricker Member

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    Great post and pretty much summed it up.
    Unfortunately some people didn't read it.

    R
     
  12. drbob1

    drbob1 Silver Supporting Member

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    Actually I've owned really similar versions of 100w and 50w amps (2 jcm800s and two early 70s Marshalls). There really isn't a perceived difference in maximum volume between them. The 100w has a lot more attack and a LOT more bass (due to the larger transformers-even if you take out two tubes so it's 50w it still has more bass and attack than the 50w). The reason a 100w amp works so much better outdoors has more to do with this higher overhead for attack than increased perceived volume...
     
  13. B_of_H

    B_of_H Member

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    technically (or so i've read) a 100w amp is only 10%-12% louder than a 50w amp.

    just sayin. (I really don't remember where this came from but I think it was an article on tinnitus and decibels)
     

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