[LAU] Impulse Response Files for Guitareros

[fons at kokkinizita.net]

On Fri, Sep 10, 2010 at 06:29:18PM +0200, Renato wrote:

> > If you record the impulse response of a hall, the resulting audio
> > file, when applied programmatically to a signal, will process that
> > signal against the "properties" it had recorded.
> > 
> 
> ok... is it the same for impulse responses of amps/cabinets?
> 
> then, if I understand correctly, these files are convoluted with the
> signal... this means that the overall effect will be equivalent to a
> specific equalization, or to some type of reverb...or both? 

It's exactly the same thing in boht cases, the only difference being
that reverb IRs tend to be quite long (seconds), while 'EQ' IRs are
usually short (a few tens of milliseconds).

A reverb is just a filter with a very bad phase response :-)

What happens in convolution is:

* each single sample of the signal is replaced by the complete IR,
  starting at the same place at the sample, and multiplied by the
  sample value,
* all these scaled and shifted IRs are added together to form the
  output.

It's a gigantic computation for long IRs, but there are tricks to
accelerate it.

Ciao,

-- 
FA

There are three of them, and Alleline.