Quote:

Originally Posted by

**gidi**
First of all thank you for your willingness to help.

Basically I'm trying to understand the way a digital EQ is performing its' boosts or cuts.

I thought that generally this is achieved by a designed IR which is convolved with the i/p signal to produce the o/p signal.

I guess in this algorithm this is not the case.

So how does it work then?

What are the stages in this algorithm?

With an infinite impulse response you can't use convolution, because it would require an infinite amount of time. With FIR filters you can do that.

Maybe it clarifies to follow what happens to an impulse.

the input is: x(0) is 1 and all other x(n) are zero.

y(n) is the output.

y(0) = alpha*x(0) - alpha*x(-2) + chi*y(-1) - beta*y(-2) = alpha*1 because other parts of the sum are zero

y(1) = alpha*x(1) - alpha*x(-1) + chi*y(0) - beta*y(-1) = chi*alpha*1

y(2)= alpha*x(2) - alpha*x(0) + chi*y(1) - beta*y(0) = -alpha*1 + chi*chi*alpha*1 - beta*alpha*1

From this on it gets only more messy but the principle is the same. If you want to know why it works, you may be out of luck, that requires knowledge on complex analysis and z-transform. But you may think of it as an algorithmical way to replace convolution and a stored impulse response.