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confused by power ratings!!!

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Paul G. OBrien:

--- Quote from: Bryan Booth on January 26, 2011, 11:55:07 AM ---  Knowing what little I do...Subs consume more power than full range speakers, so I am guessing that I would need a sub that should handle more power than my mains.  Mains are 1000w peak, we run them at 700w, so we need a sub that can handle more than 1000w. Is my train of thought on the right track?
--- End quote ---

Yeah you're on the right track though you made another common statement that probably doesn't reflect reality. "Mains are 1000w peak, we run them at 700w". The running them at 700w part is only true if the amp is pushed to maximum output all the time, at anything below this the actual power level the speakers are dissipating could be as little as 1/2 to 1/4 of that level.

And while it is true in general that low frequencies take more power to reproduce this only holds true if the subs have the same sensitivity as your mains, if they are more sensitive then it is entirely possible they will require equal or less amp power than the mains to achieve the desired sound balance. For example your Yamaha mains have a 98db sensitivity, if you want 3db more sub output than your mains you need 98db subs that can handle 3db more input power than your mains, or subs with 102db sensitivity and the same power handling, or subs with 105db sensitivity and 1/2 the power handling.

Patrick Tracy:
What TJ said. To simplify, watts is the number you consider last, after you've chosen your sub or at least narrowed the choices to the ones with the required output, size, weight, cost etc.

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