A speaker has an efficiency and this is defined as how much sound, or how loud, a speaker will go given an input of 1 watt at a distance of 1 meter.
A figure of 98db means that with 1 watt input that speaker will have an efficiency of 98db. An increase of 3db is a doubling of output so a 101db speaker will be twice as loud as a 98db speaker. As the 101db efficiency speaker is twice as efficient as the 98db speaker it will only require half the amplifier power to get the same volume hence, [i][color=#282828][font=helvetica, arial, sans-serif][b]120db with a 98db/w speaker at 1 meter you suggest 200w, but if that goes through a 95db/w speaker then it needs a 400w head, or only 100w with a 102db/w speaker[/b]. [/font][/color][/i][color=#282828][font=helvetica, arial, sans-serif]There is a lot more to it than that of course, but that is the basic principle.[/font][/color][i][color=#282828][font=helvetica, arial, sans-serif] [/font][/color][/i][color=#282828][font=helvetica, arial, sans-serif]I hope that explains it for you[/font][/color][i][color=#282828][font=helvetica, arial, sans-serif].[/font][/color][/i]