A good way of looking at this intuitively, is to think of R as dropping the level, and L
as shunting the LF's around the level pad, and C as shunting the HF's around the level
pad.
These components, including the resistor, will need to be of the highest caliber, in order to not adversely impact the performance of the speaker system. The resistor R will need to have a dissipation rating that is close to equal to the full rated power of the speaker system, or it could begin to limit dynamics due to heating effects, etc. Use of less dissipation capacity here is not going to help things at all. Like wise, the inductor L will need to have a low DCR, just as the normal series woofer inductor, to maintain a low DCR at LF's.


If your speaker is too loud at certain frequencies, this is regarded as irritating.
Therefore you have to use a Notchfilter removing a rise in the frequency response. In the following the frequencies and their damping in dB is indicated when the RCL crossover component is fitted. Please enter the loudspeaker impedance (4, 8, 16 or even higher Ω) and the corresponding correction values (frequency f_{max}, damping d_{max}) and adjust the width of the lowered curve with the buttons > < or <> To calculate existing Filters, enter the Filter Values (R, C and L), to calculate the Level of damping (dB) from this Filters. Attention: the calculated level reduction in the frequency response is only correct, if the entered loudspeaker impedance matches the measured value. At the resonance frequency this is surely not the case; here, the level drop is a lot less severe, since the impedance of the speaker is higher. 

It is difficult to establish hard and fast rules for these types of filters, so trial and error play an important part. Find f_{max}, the midpoint of the peak, and its magnitude in dB. Also locate the 3dB frequencies f_{1} and f_{2} Increasing the value of R will increase the depth or Q of the notch. The L/C ratio creates a fairly narroe filter shape (hight Q) which should work for the most peak situations. If a wider filter shape is desired use smaller values of C and proportionately langer values of L. As long as the product of L x C is the same number, the circuit resonance will remain the same but the Bandwidth will change! 
Components Parallel Notch Circuit (Dickason)  Amplitude Parallel Notch Circuit  Impedance Parallel Notch Circuit 