[sdiy] Looking for cheap lowpass filter algorithm

[Seb Francis]

Seb Francis wrote:
>
> So the only factor why it sounded nice must have been that it had a 
> very gentle amplitude roll-off compared to higher order filters.  This 
> fits with my experience with analog EQ: that I almost always prefer 
> the sound of EQ with a very gentle, wide curve (although of course 
> with analog EQ/filters there is phase distortion going on as well).
>

Just to elaborate on this .. most sounds have a whole series of 
harmonics diminishing in amplitude as they get higher.  When you put a 
sound through a very steep low pass filter you suddenly remove all the 
harmonics above the filter and leave the ones below it as they are.  
With a more gentle filter you get a gradual transition from normal 
harmonics to no harmonics.  Maybe the ear/brain prefers this?

Anyway, enough of my pseudo-scientific guess work .. :)

Seb