This is about pure and simple electronics, but it has a fact in it, that I never thought about.
Untill recently, that is. Hence the reason for this page.
When dealing with audio amplifiers, we offen turn to the subject of how many watts should it be rated.
The more the better seams like a fair idea.
But have you (yes you, the geek who wants to know this), messured the signal on your speakers when playing??
If you did, stop reading here, this will sound dull and repeating old knowlege...
Right, lets get on with it shall we..
If you set your sterieo to a normal level, the level you would hear the news at, or soft music, somthing that
you could still have a conversation in over the dinner table. or the level of witch you normaly tune in your tv to.
Now, replace the music with a pure sin-tone, say 1Khz.
Ring any bells? (sorry..)
messure the voltage on your speaker terminals, a scope is best, but a DMM should be able to give somewhat a okay reading
mind you, and standard DMM is not built for any AC voltage except for 50-60hz, but you might be lucky and have a TrueRMS DMM
that goes up to as high as 20Khz, like the Fluke 89 V series.
how many volts did you messure??
how many watts is that, when you use the rated resistance of your speaker? (4-8ohm)?
what? only about 0.9-1.2mWatts?? thats 0.001W?? are you insane??
you got a large speaker, a 100Wrms mofo of a amp, and you only output 0.001W in the speaker? somthing wrong with you??
Need not to worry, your mental problems are not caused by this.
Speakers has a rating called "Sensitivity", a figure made to ilustrate the relationship between watts going in and soundpresure comming out
a normal home-use speaker has about 85-90dB soundpresure at 1meters distance, WHEN THE INPUT POWER IS 1 WATT.
Notice the last part there? 1W input gives you the soundpresure allmost of a jack-hammer, at a distance of 1 meter.
when you watch tv, the the soundpresure is about 60dB.
Your messurements, was 0.001W, and we now know that 1W = about 90dB. so your output was 1/0.001 = 1000 times smaller.
1000 times = 10 x log(1000) = 30dB.
Would you look at that.. 90dB - 30dB = 60dB, the soundpresure level of a tv...
Think about it, makes sense.
If not, take a look that the source that made me realize all this: wikipage about loudspeakers
So, this Foo just claimed a 1W amp is all you need? wrong... (doh!)
a amplifier must not only output a power into the speaker, it must also control it.
Ordnung must sein, as we all know.
When it comes to speakers, they are like wo... they need to be forced up and down, back and forth (depending on the oriantation of your SPEAKER), in order to do this, you will need power/current
to force the coil in the speaker the way you want it. a pure sine is the most easy, and the lower the freq the better, within the range of the speaker, going too low and the speaker wont find it funny and you need to force it even more
take a large voltage change, somthing close to a square puls, that is a sudden change in current, as a reactive compoent (a cap or coil), the speaker dont like that. it needs to be forced even more.
thats why you "need" a high power rating on your amplifier.
Just for the record, I do not have problems with women...