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-- New to Convolution

New to Convolution

I just recently sold my mpc and started using battery and a trigger finger for drums, but I feel as if my drums sounded different when I was just recording from the mpc into my emu1820. I know about convolution reverbs, and how people make impulses of compressors and preamps. So, are there any impulses floating around of samplers and drum machines, like the mpc, sp-1200, or S2000s, since they all have there own unique sound?

Convolutions can only apply linear transforms to a sound. I'm not sure where you heard about people making impulses of compressors, but I'm fairly certain that those can't exist, since compression is not a linear effect.

I'm not sure how you've got Battery set up, but most likely the reason it doesn't sound quite like the MPC is that drum machines actually produce different sounds at low velocity vs. high velocity. Whereas most sampled drumsets people make (except for the very high-end professional ones) use a single sample for each key or maybe a couple of crossfaded ones. Very high-quality sampled drum kits will usually have sounds recorded at several different volumes as well as very carefully tuned crossfades. Even then, it might not sound *exactly* like a drum machine.

Reverb and delay are pretty much the only impulses you'll find. Sometimes you'll find other ones, like speaker simulators. But I've never heard of an impulse for a sampler or drum machine. Samplers especially - those devices are made for the specific purpose of accurately replaying a recorded a sound! Someone could theoretically make impulses of a sampler's internal *effects*, but again, I've never seen it done. With drum machines, people will usually just record each note at many different volumes.

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Originally posted by DigiNut [FONT=Tahoma][COLOR=#99CCEE]Convolutions can only apply linear transforms to a sound. I'm not sure where you heard about people making impulses of compressors, but I'm fairly certain that those can't exist, since compression is not a linear effect.

They do exist, focusrite has a compressor which emulates old classic compressors up to top notch level. The only way to emulate the effects is to study the sounds they make. Based on that I think you could call it a convolution compressor? just like reverbs based on actual environments are convolution reverbs. (I looked it up, it's called the Focusrite Liquid Channel and it is a convolution compressor)

to answer the question, I don't think there are plugs which emulate the sound of an mpc...

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Originally posted by Storyteller They do exist, focusrite has a compressor which emulates old classic compressors up to top notch level. The only way to emulate the effects is to study the sounds they make. Based on that I think you could call it a convolution compressor? just like reverbs based on actual environments are convolution reverbs.

That is not what convolution means. Convolution is a specific mathematical process which takes an input function and a system function (impulse response) and converts it to output with a specific formula.

I can't really write the formula too well in this little box, but just google "impulse response" and you should find many pages which explain the process.

The impulses responses can be created as wave files by deconvolving the output with its input, but that's only possible for a linear system.

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Originally posted by DigiNut That is not what convolution means. Convolution is a specific mathematical process which takes an input function and a system function (impulse response) and converts it to output with a specific formula.

thank you, this is exactly what compressors do too. changing a signal according to some algorithm. The effect I mentioned is a convolutional compressor as these algorithms are emulated/copied to get the same result out of this digital compressor as you would have using a classic compressor. 1 to 1 comparisons have shown this compressor to be able to copy some top of favourite old-school compressors.

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I can't really write the formula too well in this little box, but just google "impulse response" and you should find many pages which explain the process. The impulses responses can be created as wave files by deconvolving the output with its input, but that's only possible for a linear system.

I think you're underestimating the knowledge of these days top technicians in sound.

an actual quote from the focusrite website:

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The Liquid Channel The Liquid Channel is a revolutionary professional channel strip that can precisely emulate any classic mic-pre and compressor. Combining radical new analogue preamp technology with Dynamic Convolution� techniques, it's the ultimate fluid vintage collection.

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Originally posted by Storyteller thank you, this is exactly what compressors do too. changing a signal according to some algorithm.

Ok, I am not going to say this again. Convolution DOES NOT MEAN simply "changing a signal" or "reproducing" an existing sound somehow. It is a specific mathematical function (NOT "some algorithm").

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I think you're underestimating the knowledge of these days top technicians in sound. an actual quote from the focusrite website:

If you actually read their whole FAQ other than just the marketing tagline, you will see this:

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Q: How can convolution emulate the interaction of mic-pre and microphone? A: On its own it can�t. You need a separate analogue circuit to be present and to work with the convolution engine.

So you see, this thing is not just a convolution processor. It actually has a compressor and other analogue circuitry inside it. Convolutions (FIR or IIR) can always be implemented on a DSP chip - whenever something requires analog circuitry, it is no longer a digital system, and that means it can't be done on a computer.

Look, I'm an electrical engineer. I took two years studying signal processing, which means I spent two years studying convolutional transforms (as well as other transforms) and impulse response. I *think* I know what those things are. I'll repeat this once again: Convolution is a linear transform, and compression is not a linear effect. It's impossible to measure an impulse from a compressor and load it into SIR - what the folks at Focusrite did was probably take hundreds of thousands of impulses over a huge dynamic range and implement some switching and summing circuitry.

Guess you're right. And I thought I knew at least something
no hard feelings

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Originally posted by Storyteller no hard feelings

'course not... it's the internet!

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