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envelope filter vs wah

Discussion in 'Effects [BG]' started by mpayne86, Dec 6, 2012.

  1. mpayne86


    Aug 14, 2012
    I am have a very hard time finding out what the big difference between an envelope filter and a wah pedal is. I understand what a wah pedal does, (synth wah, auto wah, etc) but ive never got a clear understanding of a envelope filter, from the demos ive seen it seems the same to me, i must not be hearing the differences.
  2. Wah is a form of envelope filtration. That's as simple an explanation that I can give.
  3. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    They are hugely different in HOW they operate, but similar in that they are both "filter" fx. The wah is maually swept with the treadle, while the EF is triggered by the input signal.
  4. Roscoe East

    Roscoe East

    Aug 22, 2011
    An Envelope Filter (or, more properly, an Envelope-Controlled Filter) correlates the intensity of your playing (specifically, the strength of your attack) to the center frequency or cutoff frequency of a filter. It's a Voltage-Controlled Filter being automatically modulated by the output of an Envelope Follower. Play softly, and the filter barely opens up; its fc remains fairly low. Play very aggressively, and the filter opens up fairly wide; its fc goes high.

    In contrast, a wah-wah pedal correlates the physical position of the pedal to the center frequency or cutoff frequency of a filter. It's a Manually-Controlled Filter whose fc is determined by a potentiometer mechanically connected to that pedal. Push the pedal down and fc goes high, push the pedal back and fc goes low (or vice-versa). It doesn't care about the intensity of your playing, the filter just opens or closes as a result of moving the pedal.
  5. scottfeldstein

    scottfeldstein Supporting Member

    Jun 20, 2011
    West Bend, Wisconsin
    They are the exact same thing..with one exception.

    On the wah pedal, the filter sweep is controlled by the foot pedal.

    On the envelope filter, the filter sweep is controlled by how hard you play.
  6. mpayne86


    Aug 14, 2012
    thanks guys :)
  7. alec


    Feb 13, 2000
    Perth, Australia
    Synth wah and auto wah are envelope filters.
  8. kevteop


    Feb 12, 2008
    York, UK
    This is totally wrong. The 'envelope' in the name 'envelope filter' (which itself is a shortening of 'envelope-following filter') refers to the amplitude envelope of the input signal. The filter responds to that envelope - if you play louder, the filter opens further. As the note decays, the filter closes. On good envelope filters there are controls to tweak this behaviour to get a filter that responds exactly the way you want. For me, the Meatball circuit is the best I've ever come across in terms of tweaking the response.

    A wah doesn't deal with envelopes at all. The filter cutoff setting is governed by the movement of your foot on the treadle rotating a potentiometer inside the pedal.

    To the OP: Yes they are both types of modulated filter, although most wahs are band-pass filters whereas more envelope filter pedals tend to use low-pass filters, but this is purely because guitarists like wahs and bassists like envelope filters. Band-pass filters on bass can be cool but they don't give you the extreme effects that you can get from a low-pass filter. At least not a standard-tuned bass with a well-balanced sound.
  9. Any difference to a Dunlop or other "Bass Wah"?
  10. Yes. Every manufacture makes them different. Its like asking "Any difference to a Chevy or other "Pickup trucks?"
  11. rsmith601

    rsmith601 Gold Supporting Member

    Apr 14, 2009
    Boston, MA
    President, Source Audio
    An envelope filter is a technical term and describes something specific that we can all agree on. Many have explained it above.

    A wah wah is an Onomatopoeia, a word that sounds like its meaning. I am told that the word came about to describe the sound made when a bell was used with a trumpet.

    In our effects industry the word wah wah comes up 2 ways most commonly: The "Wah Wah pedal" which is described above (a filter controlled by a foot pedal). The "auto wah" which is the same as an envelope filter.

    The confusion in all of this relates to the fact that one word is a technical description of something, while the other word is not.
  12. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    No. Neither "synth" nor "auto" necessarily describes envelope following. Very often they mean a filter controlled by an LFO.
  13. rsmith601

    rsmith601 Gold Supporting Member

    Apr 14, 2009
    Boston, MA
    President, Source Audio
    Ah, that is a good point. "auto" while generally considered to be most associated with an envelope follower, would also need to include other forms of autonomous control such as an LFO.
  14. alec


    Feb 13, 2000
    Perth, Australia
    Fair point. I was thinking of the Digitech Bass Synth Wah and Boss Auto Wah pedals. But looking closer at the Boss one, it works just as you described!
  15. My bad. I meant "is a crybaby bass wah pedal conceptually different from a crybaby guitar wah pedal". I wondered if some bass versions might be based on an envelope filter like "auto wah" pedals.

    Years ago I tried a regular Crybaby on my bass but it wasn't doing it for me. I've never seen a bass wah pedal.
  16. dylanjosef


    Feb 1, 2010
    I believe that the dunlop 105q bass wah only applies the wah to the upper and midrange frequencies. I believe this is so you can still keep the basic note in there.
  17. I think, but am not sure, that the guitar wah is actually a peak or bandpass filter (which cuts off the highs and lows around a center frequency, but still changes the center frequency with the pedal), and the bass wah is a low pass filter with the pedal controlling the cut-off frequency. 90% sure, but not absolute. A quick internet search didn't show up anything, but I'm sure the info's out there somewhere.

    Edit: Yup, all the guitar versions of the Cry Baby have bandpass filters. I didn't see anything too specific for the bass version. Their website's FAQ about all the Cry Baby products indicates that it might be bandpass, but the description of the individual effect describes it as only affecting mid- and high frequencies, suggesting a lowpass. I think it is lowpassy, but they just didn't mention the specifics of the bass wah for simplicity's sake.