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Re: Filtering Techniques

Subject: Re: Filtering Techniques
From: Walter Knapp <>
Date: Wed, 23 Jun 2004 02:59:25 -0400
From: Marty Michener <>

> Rob makes terrific points, here, [which must be as arcane-sounding to Mac 
> users, even as many of their points have seemed to me for three 
> years].  The delay he points out in having a shift in a node make a 
> difference to sound, is about 1 - 2 seconds on my Home Ed. XP, build 5.1, 
> with 216,600 kbytes of physical memory available.

Yep, strange and arcane. But understandable. As much as you can, test 
your sound on multiple playback systems. And know the equipment you use.

> As Rob suggests, after you get all done, you often realize: "Oh! At step 2 
> (of eight) I did "X" wrong.  To remedy this, IF you have saved every step 
> in the process, you can go back to Step 2, and many of the filters, etc. 
> will still remember their last settings, and you can re-do steps 3 through 
> 8 again.

If you have the ability to set up the filters in a stack and audition 
the entire effect while tweaking them all, that's even better. Filters 
interact with each other, and applying one at a time you are trying to 
predict those interactions without hearing them until the end. This 
ability is being added to quite a few programs now.

I've found all too often if you tweak step 2 your ideal settings will 
shift. and not just for the filters afterward. Every filter step has to 
be rechecked. It's all that back and forth that eats a lot of the time.

> Make the filter do as little, as gently, as possible, to make the b.g. 
> noise bands fall within the same loudness ballpark.
> Do it all with a single complex curve, not with repeated passes.
> Save the filter as a named filter file if you have any doubts, and save any 
> re-dos for application to similar sound problems.

I've already commented that I don't necessarily go along with single 
filtering vs multiple passes. Try both, sometimes one way works best, 
sometimes the other.

Your filtering should be as transparent as possible, given it's purpose. 
Always be aware of the final product. A ID clip is very different from a 
full ambient recording of many species.

I tend to think of various dimensions of filtering. Most people filter 
primarily along frequency lines. The people who equate filtering with 
EQ. But you can also filter along time lines, working on just a short 
segment. And, with some filters you can filter along loudness lines. 
Each has advantages and disadvantages. And a mix of the three is easier 
to hide than just one.

Walt




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