# Understand how a low pass filter

1. May 6, 2004

### Xiox

Hi, I'm new into this subject.

I'm trying to understand how a low pass filter (where the frequency f is from 0 Hz to $$f_u$$ ) for a speacker is working. The fuction for the low pass filter is $$\mid H \mid = U_out / U_in$$, that is

$$\mid H \mid = R / \sqrt{R^2 + ( \omega L )^2}$$

where

$$\omega = 2 \pi f$$

That I don't really understand is how $$f \rightarrow 0 \Rightarrow \mid H \mid \rightarrow 1 = \mid H \mid_max$$ (f is the frequency) and $$f \rightarrow \infty \Rightarrow \mid H \mid \rightarrow 0$$. I believe that I would need a graph.

Last edited: May 6, 2004
2. May 6, 2004

### Xiox

Gm, I've reckoned it out, I quess it was too persceptible to percieve, sorry.