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Comb filtering is the basis of alot of effects. As mentioned before, choruses, digital delays, phasers and flangers are all based on comb filtering.
Someone mentioned in another thread how BT gets these lush pluck sounds - hes basically adding a long reverb tail to the synth and gating the output so it colours the sound with the verb but cuts off the reverb tail which would otherwise muddy subsequent notes and cause all kinds of phasing problems to occur somewhere further down the line, in the mix.
Alot of these neat sounding tricks and effects all come back to the same principles. Phase modulating processors (based on comb filters), frequency attenuation (based on filters) and dynamics processors (compressors and gates).
You can add various other modules like these to the signal chain to create more complex effects.
A phaser for instance is typically a comb filter with a phase splitter to generate a +LFO and -LFO. Changing the Phase init changes at what point along the horizontal axis of the waveform, it starts its oscillation from. Then you can put a high pass filter in series after the +LFO to limit the destructive phasing to certain frequency ranges.
And yea, you can build a crude phaser just by generating a stereo sound, delaying one of the channels in the stereo pair by less than 1 millisecond to get a comb filter then sticking a phase splitter straight after it. If your synth building or coding is good you can even build a basic FIR filter (i.e. write the entire process on DSP) and stick it in series after the the +LFO or -LFO and you have a rudimentary phaser without using any plugins or buying any expensive stompboxes.
The biggest problem with VST effects and outboard, all in one processors is that people grow up making music on these things and they have no idea of the signal chain inside these things. I would say it can be damaging because you get alot of people that dont realise that all these complicated phaser plugins are simply comb filters, LFOs and FIRs. There is a tendancy to think of all these things as separate processors - a phase, a comb filter, a filter, an oscillator. But really you can boil everything down to modules which alter the 3 properties of sound - amplitude, frequency and phase.
The most basic of these modules is the gate, the filter and the comb filter, respectively.
Ever use a multimode filter before? IF you have, you will know that you can build pretty much any frequency/phase modulating effect on one. Wah Wah pedal effects, phaser effects, chorus effects, stereo delays, wobbling sounds etc etc.
The genius of it is that it is all incredibly simple when you work out how its done - like most of the great inventions when shown how they work - 'if only I had thought of doing it like that!'. The important thing that separates them from us is that they thought of doing it on initiative and we didnt.
I recommend reading as much as you can on the subject and peripheral subjects. Its a cliched expression but knowledge really is power. If you do the homework, you will find using all of those tools makes much more sense later on and you start to learn every tiny detail in the sound and what you are affecting by changing a variable.
I recommend reading this mini article on the subject of phasers:
http://www.harmony-central.com/Effe...Phase_Shifting/
| quote: | | Ahm.. Thats not a comb filter hmm, or it is kindof but when you do it on left and right channels its just "delay on the other channel". And it sounds wacky when played in mono... and thats not good. |
Yes, phase modulation to a greater or lesser extent destroys mono compatibility. But if you listen to alot of modern records there is alot of dynamic stereowidth and phase modulation going on. Theres a soundclip of the end of flaming june somewhere around here (very recent) and if you take a listen to that pretty much every sound (bar 1 or 2) in that clip is panned off centre. Quite a few of those sounds have phase modulation effects on them and even more of them are progressively widened in stereo. I think I can even hear some sounds getting wider and narrower in stereo too.
Its so difficult to create the illusion of 'real space' without working with stereo width and phase. you cant really do it with just amplitude and frequency alone. And whether you like BT or not, he is very good at making his records sound as if they are playing from a real live space. Sounds are swooping around all over the place and coming at you from all different directions. Thats part of the great art of mixing - having all of these instruments moving around each other and coming at you from all angles without sounding weird or causing so much destructive phasing you completely lose mono compatibility.
Nine Inch Nails did that alot with 'Broken' and it comes with a 'not mono compatible warning.' Sure enough, sum both channels for the song 'happiness in slavery' to mono and take a listen. Whole parts of the track disappear mid mix! Thats some serious destructive phasing. However in stereo it doesnt really sound weird and you dont really get that 'brains being sucked out of your ears' sensation when you listen to a record thats phasing all over the place. Thing is, theres never an instance in that tune where the destructive phasing is so complete you are left with a 'hole' in the centre channel. Its very well mixed and theres alot of dynamic elements moving around so you never get that brainsucking sensation for very long.
In the end, it still comes down to how you plan your mix and how you keep a balance of all the instruments from left to right and quiet to loud, front to back.
Last edited by Derivative on Jun-12-2006 at 18:53
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hmm, or it is kindof but when you do it on left and right channels its just "delay on the other channel". And it sounds wacky when played in mono... and thats not good.
