Watts Louder? Light bulb or Amp?

[Fusioninspace]

So we talk about 100 watt amps and how loud they are. Does a 100 watt light bulb output the same amout of energy???? Sound/heat vs. light/heat?

 

[Light]

It's a bit more complicated than that, but essentially yeah. Voltage x Current(amps) = power(watts). Most amp ratings are, first of all, an average when you are really cranking it, and second of all mythical (i.e., a manufacturers marketing bullshit).


Light

"Cowards can never be moral."
M.K. Gandhi

 

[surfmaster]

speaker and power section efficiency also have a lot to do with how much physical sound pressure is produced.

 

[boingoman]

Here's some more to think about- in both amps and light bulbs, most of the energy is heat.

5% is considered pretty efficient for a speaker. So if you feed a speaker 100W, 95W is thrown away as heat, 5W is used to move the cone. So your 4X10 Marshall cab fed by your 100W Plexi head blasting away at full volume is really only getting 5W out it's front.

Of those 5W, only a minuscule fraction reaches your ears, because of the poor coupling between the speaker and the air.

0dbSPL= .00000000001W
100dbSPL= .00001W

The rest is lost as heat.

 

[boingoman]

speaker and power section efficiency also have a lot to do with how much physical sound pressure is produced.

Speaker efficiency will tell you how much SPL per watt you will get.

As far as the power section, a more efficient amp will get more power to the speaker per watt drawn out of the wall. But amps are rated for their output power across the outputs, so a 100W amp can output 100W. Power section efficiency will determine how many watts it needs to pull from the wall to deliver that 100W.

 

[dementedchord]

also remember that when you see 100wts on an amp that's to the speaker output and has nothing to do with the total consumption of the amp... most amps being terribly inefficient...

 

[Henry Mars]

A watt is nothing more than a measure of the amount of energy expended in the process of doing some sort of work.

In a 100W light bulb all of this energy is used to heat a filament and produce light. Heat is a by product of the resistance to the current. Here you need the heat to make the bulb glow.

In the case of an electrical current driving a speaker at 100W you want 100% of this 100W to be converted to sound energy. This is impossible because a good deal of this energy is going to be lost due to heat loss (e.g. the electrical resistance of the voice coil), loss due inefficiency electromagnetic field coupling in the transformer and speaker coil, the size and type of permanant magnet used in the speaker, and the type of material used in the speaker cone, and the way the cone is attached to the speaker frame.
In an efficient speaker these effects are minimized and optimized so that a higher percentage of the 100W is use to produce the mechanical energy to move the speaker. With a more efficient speaker more of this 100W is used to produce sound, less is wasted and the speaker is louder because more of this electrical energy is converted to mechanical energy and not lost.
I have neglected cabinet design here but it also is a big factor. If the speaker enclosure is unable to allow the proper volume of air to be exchanged efficiency will suffer.

 

[surfmaster]

A watt is nothing more than a measure of the amount of energy expended in the process of doing some sort of work.

In a 100W light bulb all of this energy is used to heat a filament and produce light. Heat is a by product of the resistance to the current. Here you need the heat to make the bulb glow.

In the case of an electrical current driving a speaker at 100W you want 100% of this 100W to be converted to sound energy. This is impossible because a good deal of this energy is going to be lost due to heat loss (e.g. the electrical resistance of the voice coil), loss due inefficiency electromagnetic field coupling in the transformer and speaker coil, the size and type of permanant magnet used in the speaker, and the type of material used in the speaker cone, and the way the cone is attached to the speaker frame.
In an efficient speaker these effects are minimized and optimized so that a higher percentage of the 100W is use to produce the mechanical energy to move the speaker. With a more efficient speaker more of this 100W is used to produce sound, less is wasted and the speaker is louder because more of this electrical energy is converted to mechanical energy and not lost.
I have neglected cabinet design here but it also is a big factor. If the speaker enclosure is unable to allow the proper volume of air to be exchanged efficiency will suffer.

so i was right!

 

[Henry Mars]

Yea... I tend to get carried away.