Understanding filter Bandwidth

[oxygen8]

Hi There,

I am studying a Multiple Feedback band pass filter, I have made changes to the Fc of the circuit to give an octave above 1122, to 2244 and an octave below 1122 to 561 with the same Q.

I have done this successfully but I am confused why if the Q has stayed the same Q=1.87 why does the bandwidth double with frequency, :

BW = Fc/Q

so  561/1.87 = 300
     1122/1.87 = 600
     2244/1.87 = 1200

Could someone explain why there is this doubling of BW with frequency while maintaining Q.

Thanks All!!!!

Jim