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Old 12th August 2004, 02:51 PM   #1
edsmith is offline edsmith  Australia
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Default Wattages & Loudness: ?I'm Lost?

I kind of gathered from reading post/articles that tube amplifiers rated at 10w will be not much different in max volume to say a 20watt amp.

Could someone please explain this in more detail. Are the average joe's out there being in a way misled when told a 100 watt amp will be twice the volume of a 50watt. I'm talking guitar amps if that has anything to do with it.


Just curious,
Ed
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Old 12th August 2004, 03:21 PM   #2
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Default Re: Wattages & Loudness: ?I'm Lost?

Quote:
Originally posted by edsmith
I kind of gathered from reading post/articles that tube amplifiers rated at 10w will be not much different in max volume to say a 20watt amp.

Could someone please explain this in more detail. Are the average joe's out there being in a way misled when told a 100 watt amp will be twice the volume of a 50watt. I'm talking guitar amps if that has anything to do with it.


Just curious,
Ed
For the volume to sound twice as loud, you need 10 times the power.
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Old 12th August 2004, 03:58 PM   #3
Sheldon is offline Sheldon  United States
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Default Re: Re: Wattages & Loudness: ?I'm Lost?

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Originally posted by AudioFreak


For the volume to sound twice as loud, you need 10 times the power.
True mathematically, but is that always true if we are talking about perception?

Sheldon
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Old 12th August 2004, 04:23 PM   #4
rkc7 is offline rkc7  United States
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Want the physics?

http://www.physicsclassroom.com/Class/sound/U11L2b.html

Generally speaking, 10dB increase is double the "loudness", and it's understood that it takes 10x the power output of a speaker to have a 10dB increase in intensity or twice as loud. So going from a 10w amp to a 20w amp would probably only give about a 2db increase. The decibel is the standard unit for the smallest perceivable change in intensity, so 2db will probably not be very noticeable. Of course if you go from 10w to 100w, it should give a 10db increase. And if you go from 10w to 1000w, it should be a 20db increase or 4 times as loud. Now to be twice as loud from 1000w, it would take 10000w.... so you can see how it quickly become infeasible to really increase the sound intensity output above a certain point. Now it comes down to speaker sensitivity on how much dB ouput you get. But then you have another problem.... the longer you listen to listen to loud volumes, the louder you'll have to turn it up to get the same effect as time goes on.
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Old 12th August 2004, 05:17 PM   #5
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by rkc7
Want the physics?

http://www.physicsclassroom.com/Class/sound/U11L2b.html

Generally speaking, 10dB increase is double the "loudness", and it's understood that it takes 10x the power output of a speaker to have a 10dB increase in intensity or twice as loud. So going from a 10w amp to a 20w amp would probably only give about a 2db increase. The decibel is the standard unit for the smallest perceivable change in intensity, so 2db will probably not be very noticeable. Of course if you go from 10w to 100w, it should give a 10db increase. And if you go from 10w to 1000w, it should be a 20db increase or 4 times as loud. Now to be twice as loud from 1000w, it would take 10000w.... so you can see how it quickly become infeasible to really increase the sound intensity output above a certain point. Now it comes down to speaker sensitivity on how much dB ouput you get. But then you have another problem.... the longer you listen to listen to loud volumes, the louder you'll have to turn it up to get the same effect as time goes on.

I understand the physics. Sorry, I should have worded the question better. I was interested in perception. If you ask a test subject to turn up the volume until it appears to them that it twice as loud (however they personally judge it), how well does that correlate to a measured 10db? Or, how much does that vary from person to person. I'm sure this data would be easy for me to find, just thought it likely someone here would know.

Sheldon
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Old 12th August 2004, 05:30 PM   #6
SY is offline SY  United States
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10 dB was the accepted average for a perceived doubling in loudness, but IIRC that number is considered to be a bit too high now.

What complicates things is that this is an instrument amp- the loudness stuff is all done with non-distorting components in a chain, a sound reproduction rule of thumb. Once you add distortion, changes in spectral content with volume, acoustic feedback and the like, it gets much tougher to correlate perceived loudness with watts of amp power.
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Old 12th August 2004, 07:00 PM   #7
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As you can see, most of the subtlety comes in the 1W range. But my 10W 6V6 PP amp is still better than your 6S4 PSE. (I have more "subtlety", aka dynamic range.)

Tim
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Old 12th August 2004, 07:24 PM   #8
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Quote:
I kind of gathered from reading post/articles that tube amplifiers rated at 10w will be not much different in max volume to say a 20watt amp.
The difference will be 3dB; the human ear responds to volume changes logarithmically, so it does take on average a 10dB increase to sound 'twice as loud'. This is also affected by the frequency bandwidth and individual frequencies for that matter, but 10dB will do to keep things simple.

But this is less than half the picture, as the output of an amp in watts is almost meaningless when compared to the sensitivity of the loudspeakers being used. A loudspeaker sensitivity increase of 3dB gets you the same result as doubling wattage with no power increase. Loudspeaker sensitivities can run anywhere from 85dB/watt to 110dB/watt on average. To get a definitive idea of how loud two different systems will be you must compare both the amplifier wattage and the speaker sensitivity to arrive at the potential dB output capabilities of the two.

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