Catching 12 khz

[SuB-ZeRo]

Hi everybody.In the picture u can see a cirsuit.This circuit was found to lock from about 139 kHz to 159 KHz.But now i am trying to find 11 to 13 KHz.
I have the formula to find how to calculate for Hz.
'''''''''''''''''''''''''''''''''''''''''''''''''' '''''THE FORMULA''''''''''''''''''''''''''''''''''''''''''' ''''''''''''''''''''''
BW = 1070 sqrt(Vi/foClf) in % of fo. Clf is in μF, Vi in V, and fo in Hz.
'''''''''''''''''''''''''''''''''''''''''''''''''' '''''''''''''''''''''''''''''''''''''''''''''''''' ''''''''''''''''''''''''''''''''''''''''''''''''''
but the problem is i don't know how to do this.I am not an engineer
i am only a novice user
if any body can send me the right cirsuit i will be really glad.
Thanks for reading my problem.