Attenuating and Shelving Filters

  • Thread starter Thread starter Robert Manor
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Robert Manor

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Whenever I read articles on mixing there are phrases like "attentuate everything above 3 kHz with a shelving filter." Can anyone tell me what the hell "attentuate" means? And what exactly is a "shelving filter"?
 
High-pass and low-pass filters are a specific type of equalizer called a shelving equalizer. A shelving EQ leaves all frequencies flat to a certain point, then turns all frequencies above or below that point down or up at a rate specified in dB per octave. Most high- and low-pass filters roll off the highs or lows at a rate between 6 and 12dB per octave.....

More info like this at www.artistpro.com ...u can sign up for free and they have some good basic information....
 
Thanks for the info! I checked out the website and registered. I appreciate your quick response.
 
I'd like to clarify what Gidge said a bit. High-pass and low-pass filters doesn't not have to be shelving. Thet can be cut-off filters too. A cut-off filter cuts everything over or under a frequency, like this:
Code: 
      v- cut off frequency
_____
     \
      \
       \
        \  <- this line will continue to go down at an angle for eternity, basically.
As you see in this example of a low-pass filter, the higher the frequencies, the more it will be cut. It is typically dampened with 6-24db per octave. You will mostly find these in synthesizers.

The more common type of filters are the shelving ones. A shelving EQ does something like this:
Code: 
     v- cut-off frequency
____
    \
     \_____
Here you see that over the cut-off frequency all frequencies are affected an equal amount. It can also not just cut, as the cut-off does, it can also boost. The bass and treble filters of stereos work like this. So when you pump up the bass, it takes all the frequencies below a certain point and boost them.

There are also "band-pass" filters, "notch-filters" and load of other types. There must be some good web page on this around...
 
Nice graphs Regebro- very helpful. And thanks for the website references. Now can you tell me what the verb "attenuate" means? Does that simply mean "adjust" or does it have some other meaning? Maybe I should just check the dictionary, eh?
 
Thanks Vox- and all of you

Thanks to all for answering my questions. I'll put the information to good use. I just ordered a pair of Alesis M1s. Can't wait!
 
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