It ain't that difficult.
Whatever6750 said:
Is there some kind of chart to use to figure out how many db you would get with xdb sencitive speakers at x amount of watts?
For each doubling of power you get another 3 db of "sound".
So, if your speakers ar rated at 90 db, you get 90 db for 1 watt of power applied. I'm sure pretty sure can plug in the numbers from whatever speaker you're considering
for 93 db, you need 2 watts
96 db, you need 4 watts
99db, 8 watts
102 db, 16 watts
105 db, 32 watts
108 db, 64 watts
111 db, 128 watts and it just keeps on going.
It's generally accepted that for an apparant "doubling" of the loudness level you need about 10 times our current power (pun intended). So, if you are starting with a 100 watt amp, you would need to have on tap about 1,000 watts for that.
Add to this that the speaker db measurements ar etaken at 1 meter from the speaker andthat foreach doubling of that distance, you lose 6 db. So, that 111 db you see above, from a little over 6 feet away, drops to about 105 db. At 12 feet you're back down to 99db or so.
Consider also that your room and it's furnishings absorb some of the sound as well. Granted, some of it is reflected back from hard surfaces but that's no treally a good thing on the whole.
Also keep in mind that efficiency doesn't necessarialy corrolate with better sound. ...just louder. Just like a car that gets grreat mileage may not be what you want when cruising the interstates for long journeys, unless gas mileage is your only concern.