Harley
March 19th, 2007, 01:49 PM
Main forum or amp forum? Wasn't sure, but this main forum currently has over 10X more traffic. Mods can move it if they wish.
I read one of those posts today where the author used the, "It's really loud for and X watt amp". I decided to put a little info out there for the newer guys/gals that might be considering an amp purchase. Some is info grabbed from the web. Some is personal experience. Please feel free to argue against any or all of it. I only have about the same level of knowledge as anyone else here that's been playing for a while. A couple years ago I started building my own tube amps and began researching what influences their sounds at the same time.
I've always leaned towards the lighter side when it comes to live performance amps. Currently I'm using a 15W Vox. Previously it was a 22W Deluxe Reverb boutique build. I've even used a 6W vintage Gibson some. These are in venues like honky tonks, biker bars, etc. Just recall the club in the movie Roadhouse and you've got a good picture of an average-sized, rural bar.
I'll list a few things that relate to what I'm trying to get across-
1 Amp Wattages
2 Speaker Efficiency
3 Tube vs Solid-State volumes
Wattage
The way that watts translate into decibels is in powers of 10. You need to go 10x higher in wattage to get twice the volume. The difference in volume between 100W and 50W is actually only 12% less. Here's a list I got from the amptone site that's surprising to some. You may have seen it a few times on other discussion forums.
40 watts is 94% as loud as 50 watts.
30 watts is 86% as loud as 50 watts.
25 watts is 81% as loud as 50 watts.
22 watts is 78% as loud as 50 watts.
20 watts is 76% as loud as 50 watts.
18 watts is 74% as loud as 50 watts.
15 watts is 70% as loud as 50 watts.
12 watts is 65% as loud as 50 watts.
10 watts is 62% as loud as 50 watts.
9 watts is 60% as loud as 50 watts.
8 watts is 56% as loud as 50 watts.
7 watts is 55% as loud as 50 watts.
6 watts is 53% as loud as 50 watts.
5 watts is 50% as loud as 50 watts.
4 watts is 47% as loud as 50 watts.
3 watts is 43% as loud as 50 watts.
2 watts is 38% as loud as 50 watts.
1 watt is 31% as loud as 50 watts.
1/2 watt is 25% as loud as 50 watts.
Formula--> X% louder = 2^log10(P2/P1) * 100%
Speaker efficiency
I swear to you, my 15W Vox sounds louder than my best friend's 40W Hot Rod Deluxe. It took a while to figure out why, but the answer was really simple once we found the below science. The speaker in mine is the Celestion Alnico Blue which has a very high efficiency rating. His speaker is the factory Fender that came stock with the amp. If we were to A/B with each others speakers I'm sure the outcome would be different. He's just one of those guys that won't make any changes to ANYTHING.
Speaker efficiency is a key to volume. That curve is also not linear. If you take 2 otherwise identical speakers, one with a sensitivity rating of 103dB, and one with a rating of 100dB, that -3dB drop is the equivalent of sending half the power into the speakers... like moving from a 100W amp to a 50W amp, or about a 12% drop in volume.
Now, if you move from the 103dB speaker to a 97dB speaker that is otherwise identical, that -6dB drop is like moving from a 100W amp to a 25W amp. That being the case, a 25W amp played through 103dB speakers is exactly as loud as a 100W amp being played through 97dB speakers.
Similarly, when one plugs a small amp into a 4X12 cab, or similar, it'll sound BIG. Even a 2-watt amp can sound huge. I've done this with a Roland Micro Cube before, installing a speaker-out feature that cuts off the amp's internal speaker when a cab is pugged in. It is LOUD. These strange experiments just ease curiosities. The Cubes are really designed for use with full-range speakers and don't sound that good with guitar speakers.
Tube vs Solid State
Peak output of tube amplifiers is heard as being up to three times louder than similar rated solid state guitar amps. For example, a 30 watt tube amplifier can be perceived by the listener to be as loud as a 100 watt solid state amplifier, particularly when both are driven into maximum distortion.
As noted, this is actually the perceived loudness you're hearing. Watts are watts, and decibels are decibels. The below statement on Musicians Friend's buyers guide, and others like it, seem to confuse many into thinking the info is fact.
Tube watts are generally louder than solid state watts, particularly in the case of Class A amps, in which five watts can generate as much sound as some 40-watt solid-state amps produce.
Below is the most common explanation why. If I typed out my own explanation I'd only confuse myself in the end:) -
There have been many speculations about the reasons for these differences between measured and perceived performance. The oldest is probably the one that points out that tube amps tend to clip rather softly, whereas most transistor amps clip hard. So when you drive your tube amp into clipping, the occasional peaks will be compressed and rounded off—not chopped off, as would happen in a transistor amp, which is subjectively far more objectionable. Of more recent date are hypotheses that it is the different harmonic-distortion spectral contents of the two technologies that account for the perceived difference in loudness.
Arguably, most amps sound best when ran close to their peak output, sometimes described as a sweet spot. This is easier to do when the amp wattage is lower. But an argument exists that higher wattage amps allow more headroom. This mostly relates to clean players. "Headroom" is the range an amp has before it starts to break up. Through wattage, one can use compromise and obtain a desired volume/breakup level.
Also remember that in most live situations you'll have a PA system, either the house's or your own. When you throw a mic in front of an amp it can be as loud as you need it. This also gives you the ability to mix it in perfectly with the rest of the band.
"Can you turn it down a little?"-
I'll get this out of the way right here. Doesn't matter what the event is...within a few minutes of the first set there'll be a waitress that asks you to turn it down some. You can see this coming in advance. You'll see a middle-aged guy, sitting alone at the bar, flag down a waitress and point at the band. It happens EVERY TIME. You could be playing through headphones and it would still happen.:) As people start hitting the dance floor you start returning to previous or even higher volumes. I hate loud music myself, but you should be able to start out at normal jukebox levels. Wouldn't you think?
I read one of those posts today where the author used the, "It's really loud for and X watt amp". I decided to put a little info out there for the newer guys/gals that might be considering an amp purchase. Some is info grabbed from the web. Some is personal experience. Please feel free to argue against any or all of it. I only have about the same level of knowledge as anyone else here that's been playing for a while. A couple years ago I started building my own tube amps and began researching what influences their sounds at the same time.
I've always leaned towards the lighter side when it comes to live performance amps. Currently I'm using a 15W Vox. Previously it was a 22W Deluxe Reverb boutique build. I've even used a 6W vintage Gibson some. These are in venues like honky tonks, biker bars, etc. Just recall the club in the movie Roadhouse and you've got a good picture of an average-sized, rural bar.
I'll list a few things that relate to what I'm trying to get across-
1 Amp Wattages
2 Speaker Efficiency
3 Tube vs Solid-State volumes
Wattage
The way that watts translate into decibels is in powers of 10. You need to go 10x higher in wattage to get twice the volume. The difference in volume between 100W and 50W is actually only 12% less. Here's a list I got from the amptone site that's surprising to some. You may have seen it a few times on other discussion forums.
40 watts is 94% as loud as 50 watts.
30 watts is 86% as loud as 50 watts.
25 watts is 81% as loud as 50 watts.
22 watts is 78% as loud as 50 watts.
20 watts is 76% as loud as 50 watts.
18 watts is 74% as loud as 50 watts.
15 watts is 70% as loud as 50 watts.
12 watts is 65% as loud as 50 watts.
10 watts is 62% as loud as 50 watts.
9 watts is 60% as loud as 50 watts.
8 watts is 56% as loud as 50 watts.
7 watts is 55% as loud as 50 watts.
6 watts is 53% as loud as 50 watts.
5 watts is 50% as loud as 50 watts.
4 watts is 47% as loud as 50 watts.
3 watts is 43% as loud as 50 watts.
2 watts is 38% as loud as 50 watts.
1 watt is 31% as loud as 50 watts.
1/2 watt is 25% as loud as 50 watts.
Formula--> X% louder = 2^log10(P2/P1) * 100%
Speaker efficiency
I swear to you, my 15W Vox sounds louder than my best friend's 40W Hot Rod Deluxe. It took a while to figure out why, but the answer was really simple once we found the below science. The speaker in mine is the Celestion Alnico Blue which has a very high efficiency rating. His speaker is the factory Fender that came stock with the amp. If we were to A/B with each others speakers I'm sure the outcome would be different. He's just one of those guys that won't make any changes to ANYTHING.
Speaker efficiency is a key to volume. That curve is also not linear. If you take 2 otherwise identical speakers, one with a sensitivity rating of 103dB, and one with a rating of 100dB, that -3dB drop is the equivalent of sending half the power into the speakers... like moving from a 100W amp to a 50W amp, or about a 12% drop in volume.
Now, if you move from the 103dB speaker to a 97dB speaker that is otherwise identical, that -6dB drop is like moving from a 100W amp to a 25W amp. That being the case, a 25W amp played through 103dB speakers is exactly as loud as a 100W amp being played through 97dB speakers.
Similarly, when one plugs a small amp into a 4X12 cab, or similar, it'll sound BIG. Even a 2-watt amp can sound huge. I've done this with a Roland Micro Cube before, installing a speaker-out feature that cuts off the amp's internal speaker when a cab is pugged in. It is LOUD. These strange experiments just ease curiosities. The Cubes are really designed for use with full-range speakers and don't sound that good with guitar speakers.
Tube vs Solid State
Peak output of tube amplifiers is heard as being up to three times louder than similar rated solid state guitar amps. For example, a 30 watt tube amplifier can be perceived by the listener to be as loud as a 100 watt solid state amplifier, particularly when both are driven into maximum distortion.
As noted, this is actually the perceived loudness you're hearing. Watts are watts, and decibels are decibels. The below statement on Musicians Friend's buyers guide, and others like it, seem to confuse many into thinking the info is fact.
Tube watts are generally louder than solid state watts, particularly in the case of Class A amps, in which five watts can generate as much sound as some 40-watt solid-state amps produce.
Below is the most common explanation why. If I typed out my own explanation I'd only confuse myself in the end:) -
There have been many speculations about the reasons for these differences between measured and perceived performance. The oldest is probably the one that points out that tube amps tend to clip rather softly, whereas most transistor amps clip hard. So when you drive your tube amp into clipping, the occasional peaks will be compressed and rounded off—not chopped off, as would happen in a transistor amp, which is subjectively far more objectionable. Of more recent date are hypotheses that it is the different harmonic-distortion spectral contents of the two technologies that account for the perceived difference in loudness.
Arguably, most amps sound best when ran close to their peak output, sometimes described as a sweet spot. This is easier to do when the amp wattage is lower. But an argument exists that higher wattage amps allow more headroom. This mostly relates to clean players. "Headroom" is the range an amp has before it starts to break up. Through wattage, one can use compromise and obtain a desired volume/breakup level.
Also remember that in most live situations you'll have a PA system, either the house's or your own. When you throw a mic in front of an amp it can be as loud as you need it. This also gives you the ability to mix it in perfectly with the rest of the band.
"Can you turn it down a little?"-
I'll get this out of the way right here. Doesn't matter what the event is...within a few minutes of the first set there'll be a waitress that asks you to turn it down some. You can see this coming in advance. You'll see a middle-aged guy, sitting alone at the bar, flag down a waitress and point at the band. It happens EVERY TIME. You could be playing through headphones and it would still happen.:) As people start hitting the dance floor you start returning to previous or even higher volumes. I hate loud music myself, but you should be able to start out at normal jukebox levels. Wouldn't you think?