KVR Audio

mistertoast · Post by **mistertoast** » Sun Sep 13, 2009 10:09 pm

antto wrote:ok, you probably wanted to know how i can tell from an audio sample so much about what's the resonance level, what were the knob values..
i can, because i've stared at oscilloscopes for about 7 years maybe, i have an idea how sounds "look like" as a waveform

i guess my brain works in an odd way ;] (don't get me wrong, i'm no genious)

It's OK. We all have our own odd fetishes.

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 12:31 am

>>SoundForge -> Spectrum analysis

OK. I have Soundforge (came with Vegas).

What did you do? I can highlight part of the wave and get a spectrum analysis, but it's only for that part that I highlighted. So, again, it seems like you need multiple snapshots. And, indeed, it does let you take up to 4 snapshots.

But from what you said, I got the idea that you had a graph of how the cutoff moved through time.

Is there functionality I'm missing in Sound Forge? What, exactly, did you do? Help a KVRAF'er out.

Did you set a number of slices? If you did, I think I have an idea of what you did to grab the peaks.

How many slices did you use?

Music Engineer · Post by **Music Engineer** » Mon Sep 14, 2009 12:50 am

antto wrote:damn, whole day i spent in trying to get the filter envelope curve
darn, it turns out it's pretty shitty, it's not a simple exponent, not a power of something, i even tryied to do something like 1/sqrt(x*something) but it failed too

i analyzed two different filter envelope sweeps now and found that the exponential decay (as delivered by the leaky integrator or multiplicative accumulator) fits it very well. here is my exponential fit of the first sweep in the sample 'orig_slide.wav' from the audiorealism site:

the blue curve is the data, the green curve is the fitted exponential decay. so - what's the problem?

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 1:01 am

I'm been using the "multiplicative accumulator" (something makes me want to call that the "geometric accumulator") myself.

Now, though, what I really want to do is write a few forensic tools.

1) Given a wave, automatically returns the base frequency and filter cutoff through time.

2)Given a function of x, a playback frequency, and a sampling frequency, output an FFT chart.

Music Engineer · Post by **Music Engineer** » Mon Sep 14, 2009 1:02 am

mistertoast wrote:But from what you said, I got the idea that you had a graph of how the cutoff moved through time.

Is there functionality I'm missing in Sound Forge? What, exactly, did you do? Help a KVRAF'er out.

dunno about soundforge, but in wavosaur it would be the sonogram function and in audition the spectral frequency display ...i actually use the term 'spectrogram' mostly

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 1:25 am

Robin from www.rs-met.com wrote:
mistertoast wrote:But from what you said, I got the idea that you had a graph of how the cutoff moved through time.

Is there functionality I'm missing in Sound Forge? What, exactly, did you do? Help a KVRAF'er out.
dunno about soundforge, but in wavosaur it would be the sonogram function and in audition the spectral frequency display ...i actually use the term 'spectrogram' mostly

I'll try Wavosaur. Thanks.

---

Tried it. It would be great as a special effect in a submarine film. Doesn't really give me numbers I want.

antto · Post by **antto** » Mon Sep 14, 2009 3:35 am

oh, excuse me, SoundForge -> Spectrum Analysis -> Sonogram, the default display is shit ;]

Robin: "filter sweep" ???
i was talking about the filter envelope curve, this graphic you posted is probably something else, it's different

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 4:02 am

Filter sweep is how the cutoff moves through time. If we aren't talking about that, what are we talking about?

antto · Post by **antto** » Mon Sep 14, 2009 4:05 am

i always thinkered that a filter sweep would be linearly moving the Cutoff knob to see the filter response
there is no such thing in the TB-303 since you always got some envelope going on and the cutoff range changes a lot depending on the EnvMod knob ;]

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 4:09 am

So does your curve describe the movement of the cutoff or not?

antto · Post by **antto** » Mon Sep 14, 2009 4:12 am

yes, but this is only the shape of the envelope (the thing that you control with the Decay knob)
not the cutoff knob
gonna upload a 1:1 comparison with the audio file i used to distinguish the knob ranges and the curve, after i get back from work

Music Engineer · Post by **Music Engineer** » Mon Sep 14, 2009 1:31 pm

antto wrote:Robin: "filter sweep" ???
i was talking about the filter envelope curve, this graphic you posted is probably something else, it's different

whe i say 'filter sweep', i mean a filter that changes cutoff frequency through time - regardless whether this sweep is created manually by tweaking the cutoff knob or imposed by an envelope. the sample i'm talking about is here:

http://www.audiorealism.se/abl/abl2_announcement.htm

the link 'Sliding' under 'Original Hardware', and the filename is 'orig_slide.wav' - although primarily demonstrating slide, there's also a strong (envelope imposed) filter sweep going on as well, with apparently slow decay time, so the shape is observable at a rather good time-resolution

btw.: there are also theoretical reasons that would support an exponentially decaying shape - analog envelope generators are typically realized with RC-circuits, which sport exactly that type of shape

mistertoast · Post by **mistertoast** » Mon Sep 14, 2009 3:14 pm

I think we should use the correct curves for the filter sweep and slide, whatever they are, even if they have to come out of a lookup table.

I'd guess that a lot of the character of the 303 is in those curves.

So I think antto's attention is in the right place.

Music Engineer · Post by **Music Engineer** » Mon Sep 14, 2009 3:32 pm

mistertoast wrote:I think we should use the correct curves for the filter sweep and slide, whatever they are, even if they have to come out of a lookup table.

I'd guess that a lot of the character of the 303 is in those curves.

So I think antto's attention is in the right place.

of course should attention be paid to the shape of the curves. but my point is that the exponential shape is actually the correct one.

antto · Post by **antto** » Mon Sep 14, 2009 3:48 pm

i'm uploading a 88200Hz audio sample of the TB-303 that i used to get the curves i'm talking about, it's kinda huge (~50mb, 22mb compressed rar)
on the left channel there is my synth (with the new curves and knob ranges)
right channel is the audio sample which rv0 recorded for me (with my specifications) (thanks to him) (TB-303)

Open303 - open source 303 emulation project - collaborators wanted