using convolution for sounds OTHER than reverb

Logic Pro X (and older versions) questions and troubleshooting

using convolution for sounds OTHER than reverb

Postby Morerecords » Tue Aug 21, 2007 7:49 pm

anyone got ideas or techniques?
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Re: using convolution for sounds OTHER than reverb

Postby breeze » Wed Aug 22, 2007 6:22 am

Morerecords wrote:anyone got ideas or techniques?

I use Space Designer as a sound design tool for SX all the time. You can load in any soundfile as the impulse, so convolving an input signal with something other than a reverb impulse response will give you all kinds of differnt things. Anything with the same basic shape as a reverb IR, such as a metallic crunch or a glass impact, will still feel reverb-like, but more of a SFX bed than actual reverb. Put in something like a glassy impact, and you can make a crystalline SFX bed, perhaps. Anything that's long, without a lot of transients, weill yield SFX-bed type results, while something with transients and spaces in between will yield layered (delay-like) results. It's a matter of experimenting, and sending the same input signal through Space Deaigner while you keep loading in new IRs (use any kind of samples) will tell you a lot.

Then you can start manipulating the amplitude envelope of the IR, and this can yield all kinds of wooshes and similar gestures. Reversing the IR will give all kinds of variations on that approach - right there is a ton of new sounds to create.

Then, add the filter to this, as well as the filter envelope, and you can make all kinds of strange and unusual sounds, depending on the input signal and the IR you choose. Between the amplitude and filter envelope, you can make a whole lot of cool sounds.

If you work with the synthesized IR rather than a sampled IR, you can also manipulate the density. A high density feels like reverb, but setting a low density yelds all kinds of wonderful stutters and so forth. Watch the IR display change when you set a low density and you'll get a sense of what's happening there. Along with the amplitude and filter envelopes, there's a whole world of cool sounds you can make with low density settings, and enveloping those settings.

If you change the IR start time so that you're into the IR a bit, and set a short duration, now you're convolving with a very short section of the IR (1-100 ms) and it's more like a filter (resonator). There's all kinds of timbral changes you can impart on a signal this way, great for anything from drum loop variations to SFX on dialog, to delay returns in a pop tune, etc. You can use almost anything for the IR in this case, although different IR's (vocal note, guitar note, car by, metallic crunch, etc) will yield all kinds of variations to the basic idea of a resonantor.

With any of these ideas, you can also set up a feedback loop (you have to use auxes for this), and send the output of Space Deisgner back into its own input again. Plus, you can process your input signal either pre- or post- Space Designer (flange it, Spectral Gate it, etc) and get even more interesting sounds.

It's all trial and error, but once you get the hang of it, Space Designer is a really fun sound design tool. When you hit on something you like, bounce it, and add it to your SFX library or whatever.
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Postby scrofani » Wed Aug 22, 2007 7:11 am

it's great for that. Grab some free IR's from Be sure to get the 16 bit ones. I don't think SD does 24bit IR's although you could batch convert with other programs if you had to. Anyway, they have lots of mic pre's and classic compressors and eq's. These won't give your audio the dynamic characteristics of the devices but they will capture the general tonal flavor of the. On of my absolute favorite impulse sets that I came across by reference on this very forum is a collection called "beamsonic." you can find it on google. The Ampeg tape machine IR's in there are stellar and can even be used on your master bus. One of these with Space designer sounds as good as dedicated expensive tape sim AU plugs you can buy - in my opinion. If you throw one across the master bus and use some of Logic's distortion plugs sparingly with a compressor you can get some convincing classic sounds.
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Postby fader8 » Wed Aug 22, 2007 9:54 am

Using odd bits of various strange audio as IR's can be a lot of fun. However, it's not the best tool if you're trying to accomplish something very specific from a sound design standpoint. That's not to say that this kind of "roll the dice" approach doesn't sometimes yield some awesome results. It certainly can. It's just that the results might not be entirely what you expect, or your ability to tweak the results may not be what you'd want.

But don't let that stop you! It can be a cool way to create new and unexpected drum sounds!
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