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Exciter

Exciter

Postby gilli » Sat Mar 16, 2013 8:27 pm

So, for round 72 a discussion about exciters came up in the one-liners.

Especially for this round exciters are an interesting tool, because the provided samples of the Fairlight CMI lack higher frequencies. While this might not be a big issue on tonal or dull sounds, it does become a challenge, if you're trying to bring bright instruments into a natural sounding mix. As you most probably know, a crash cymbal or a high hat recorded at only 11khz won't sound good anymore, if you decide to play it at its original speed (to preserve its length). And if you'd try to emphasize its highs with an EQ, you wouldn't be able to boost frequency ranges that are not present. Or you'd boost its highest available ranges, which would lead to an unpleasant and piercing sound.

Four years ago I would not know what an exciter does but after having heard some devices and DSPs that would not only apply this effect to the higher ranges, I finally knew it's not a stupid treble boost and understood how to build it. The first time I did this was in round 54. And like plusminus said, I only used it for vocals.

Luckily Renoise offers a native exciter now and some while ago I even built an exciter for Sunvox (just clicking, not a big deal). This round would be just perfect for me to demonstrate what you can get out of such a DSP but I'm not happy with my entry idea, so I'm just going to give you some background of what I have learned and a couple of audio examples, so you can judge yourself if the use of an exciter would suit your needs or not.

Background
An exciter only distorts a selected frequency range and lowers the output volume there. By doing this it adds harmonics to that range. So the 'excited' frequency band appears to be richer without being amplified.
Think of a sine wave with a normalized loudness. If you do some spectrum analysis, you'll see the very frequency of the sine wave at which it's being played. Now you would amplify this sine wave to a point where it becomes a pulse wave. Next you lower the volume of that result until it sounds as loud as the sine wave did. And finally you do another spectrum analysis and you'll see that a bunch of harmonics have been added to the base frequency of that earlier sine wave. That's pretty much all the magic of the exciter.
Originally exciters were only applied to high frequency ranges but plugIns like MaxxBass or the SPL Vitalizer apply the same trick to other bands, too. And so does Renoise with its 3-band exiter.

Demos
The following demos have been made by using only the provided Fairlight CMI samples of the current sample pack.

Demo with exciters
Dedicated exciters for percussions and tonal instruments. The exciter has also been used for low frequencies, e.g. to add some subs to the kickdrum.

Demo without any exciter
Same as above just bypassing all the exciters to show the difference.

Source file (Sunvox)

The provided sample pack is good enough though. Another attempt to make a demo in Renoise showed me that I could probably get the same color with basic eqing. That's where plusminus would be right: We don't have to use exciters everywhere.

Demo with exciters Demo without exciters Source file (Renoise)
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Re: Exciter

Postby plusminus » Sun Mar 17, 2013 8:45 am

Great example files Gilli. The excited version sounds better, but apart from the hihats the effect is very subtle. Which is how it should be usually! Unless you're going for DSP abuse of course in which case you can push the exciter effect as hard as you want...

The reason I brought up exciters originally is because a lot of the samples, especially the drums, are pretty muddy sounding. An exciter isn't the only way to fix that, but it's one way, and learning more tools is always beneficial. And it can definitely help separate a lead instrument from the background, which again might be a problem with these samples.

I made the comment that exciters "only make sense in the context of the final mix, and so probably easier to get right by putting it on the master." This is not a very good comment! :P

What I meant was similar to what Gilli said about an exciter not being a treble boost. By adding an exciter to one instrument, you make it stand out more, which is fine. But the frequencies which need to stand out kind of depend on what else you have going on in your mix. Adding it to the master channel will give your whole mix a little bit more "sparkle", as long as things were already fairly balanced beforehand. But adding an exciter to every track individually is generally a bad idea.. if you are going to do this you need to excite different frequency ranges or else there isn't much point, and EQ would probably serve you better.

As always there are no rules that can't sometimes be broken.
Singing is a trick to get people to listen to music for longer than they would ordinarily. -- David Byrne

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Re: Exciter

Postby chunter » Sun Mar 17, 2013 6:04 pm

Reiterating a little, most "period" use of the Fairlight had effects and enhancement, and other instruments played to complement it (like Linndrums and bright guitars.)
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