[guitargatler]

Originally Posted by Col. Ghillie

So why do they even use watts to describe amps? (Maybe you could tone down the technical jargon and bring it down to my level.)

haha so you'll go WOW That thing has a lot of watts it must be SUPER LOUD! A lot of it is marketing, like putting out a 120 watt amp instead of 100 watts and claiming it's louder. Basically if you have a setup that is a 50watt 1x12 combo and you want it to sound twice as loud you would have to upgrade to a 100watt 4x12 setup. There's a lot of factors involved though because a lot of it is conditional. but to break it down doubling the power to 100 watts will give you 3db's and then adding an additional 12 will add 3db's then doubling that to 4 12's will give you another 3db's which will be 9 which will pretty much sound twice as loud.

[Ryan Freeland]

Originally Posted by Col. Ghillie

So why do they even use watts to describe amps? (Maybe you could tone down the technical jargon and bring it down to my level.)

The reason? Breakup. Lower wattage amps will obtain power tube saturation at lower volume levels.

[Major Tom]

There is I'm sure some equation of the relationship of additional drivers vs SPL output, but adding 3db every time you double the amount of drivers doesn't compute. If that were the case, you could take that Epi Valve Jr. at 5 watts and hook like 32 speakers up to it and blow yer house apart. That wouldn't happen.

Here's a couple things:

When you "stack" speakers, there is a coupling thing that happens, and the dispersion is narrowed on that axis. A 2x12 combo like a Twin will have a narrower dispersion horizontally. Standing right in front of it, that narrower dispersion is going to be louder 'cause its more focused. There I think is also a coupling thing that applies to low freqs - or maybe that's due to the narrow dispersion. I can tell you from my experience in messing with 2x12's, listening to 1 speaker and then both together, that with both there is a lot more bottom end, and louder in general.

Speakers are going to compress and saturate at some point. Maybe like 10 watts of power or so, and after that the amplifier power is not getting used as efficiently. In other words,that speaker already getting about 10 watts of power - increase that to 20 watts, or 3db, the speaker may only deliver an extra 2 db increase in SPL. Increase it again by 3 db, or 40 watts, and it may only put out an additional 1 db in SPL. Try 80, and it just might flatulate and distort and not really put out any additional SPL's. The louder it gets the more saturated. Adding another speaker or 3 will divide the amp's output up so each spkr is getting less power, so it is less saturated, and putting out more SPL with each watt...

Watts as a measurement - its tradition; its just a rough gauge. the actual SPL is more related to the configuration and efficiency of the speaker(s). For combos, SPL would maybe be more meaningful, but they are going to have to rate that at some level of acceptability, speaker distortion-wise. Suffice it to say that most guitar amps are way louder than necessary.