Speaker relative efficiency/sensitivity when using a high pass filter


Is there a formula/algorithm/rule of thumb for calculating how a speaker's power requirements might change when the lower frequencies are handled by a subwoofer?  Specifically for a ported speaker with a supposed frequency response down to 35Hz and an a 89dB sensitivity with a second order crossover at 80Hz. I know it goes down but by how much? I recognize that power requirements increase as frequency decreases but is the difference enough to allow for a less powerful amp? I would think so.

 

tcutter

If you set up the subwoofer as a subwoofer, not a substitute woofer, then you'll still need the same amount of power flowing to the main loudspeakers.  With a crossover at 80Hz the main loudspeakers will still have significant output at 40Hz.

I am using a second order high pass filter at 80 Hz yielding12dB down at 40Hz.  12dB is associated with a 16-fold power difference. This is my rationale for the inquiry.

If you want your main loudspeakers to have punch and power, I would not cut your main amp back too much, preferably buy more power!