I'll try, though english isn't my first language

If genixia and I remember correctly it's like this:

Q=f_center/(f_high-f_low) <==> f_high-f_low=f_center/Q

With a Q of 1 and a center frequency of 1000Hz, the width of the affected band (>= -3db effect) will also be 1000Hz ( f_center/(f_high-f_low) = 1) -> f_high-f_low = 1000

With a Q of 5 you'd have an affected band that is 200Hz wide.
With a Q of 10 you'd have an affected band that is 100Hz wide.
With a Q of 0.5 you'd have an affected band that is 2000Hz wide (not sure how getting down towards DC affects things though).


Unfortunately I don't recall how the f_high and f_low (the frequencys where the effect is down 3db compared to the center frequency) are placed, but I don't think it's f_center ± (f_high-f_low)/2. IIRC, it's that f_center is the geometric average of the f_high and f_low (ie f_center=sqrt(f_high*f_low)), but I'm definately not certain on that point. If so, f_high can be written as f_low+f_center/Q so you get a 2nd power(?) equation to solve to find f_high and f_low.

Did that help any?

/Michael