I actualy try to code a digital equalizer with the 56k DSP. I would like to know if my way to make it is good because the final response isn't look like I want.
1) take sample x(n) from ADC
2) calculate x(n) for each filter and store each results
3) Pop out x(n), x(n)', x(n)'', ... and add each one to form y(n)
4) send y(n) to DAC
Before building a complete equalizer, I only use 3 IIR filters for testing the method.
1st filter : Lowpass Fcutoff = 1kHz
2nd filter : Band pass Fcentral 2kHz, Bandwidth 2kHz
3rd filter : Band pass Fcentral 4kHz, Bandwidth 4kHz
So the ideal bode graph should be a straigth line from 0 to 4,2kHz and then go down. But in practice it isn't look like this.
Does my method is good ? Do i miss something ?