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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
SPX style early reflections
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3phase



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PostPosted: Fri Aug 26, 2005 7:47 pm    Post subject: SPX style early reflections Reply with quote  Mark this post and the followings unread

I ve a problem to recreate the kind of early reflektion clusters you can do with the old yamaha SPX FX devices...
I am sure the G2 can handle this..but...like usual there is something more about it than just cluster a few little delay loops...
there is a significant amount of "smear" in the early reflection cluster of yamaha..
I have no idea how they are done inside Yamahas DSP...
anybody any clues?


My try to reproduce the wave form resulted in a very different sound...
It was just multiplied spikes, nothing like the goal sound.
I tried first to recreate a spx early with the lowest densety setting..
but even this simple looking pattern of a few phasereversed repeats it sounds in a spx much smoother and reverbish as my
delay cluster ...Even when the waveform looked close..there is some dispersion involved in the spx algorythm..Its not just a delay cluster...

I will experiment with robs A77 patch a bit..but if somebody has more insights in the way how these earlly reflektion algos are actually done please let me know...


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Blue Hell
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PostPosted: Sat Aug 27, 2005 5:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Whenever I say "dispersion" Rob says "Allpass".

Maybe you should make a longer allpas (multipe stages at different center frequencies in series).

My prefered solution for dispersion is convolution with a shaped brown noise burst. Not very practical on the G2 but can be nice in a wave editor.

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3phase



Joined: Jul 27, 2004
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PostPosted: Sat Aug 27, 2005 7:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Whenever I say "dispersion" Rob says "Allpass".

Maybe you should make a longer allpas (multipe stages at different center frequencies in series).

My prefered solution for dispersion is convolution with a shaped brown noise burst. Not very practical on the G2 but can be nice in a wave editor.



Yeah, the new allpass filter circuit from rob maybe helps...
I ve to try a bit with the buildingblocks in the a77 patch...too bad that i dont have a spx by hand wright now.. I ve to organize one.
As i know from my previous simulation trys it actually helps a lot when you know about the signal flow in the original algorythm.
But its pretty unlikely that a senior yamaha developer is lurking around here..or?
THese Yamaha earlies must be a very basic design...
I wonder about the pattern of phase reverses as you can see pretty well in the low density settings..
Is this indicating a modulated allpass filter in the feedback path?
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sheridan



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PostPosted: Sun Aug 28, 2005 6:53 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know much about recreating early reflections, but if I am reading this correctly, you are trying to get to the audio reflection pattern from the SPX audio clip...

To me, it looks like you need to use many more discreet echoes, each with much shorter delay times. Each should have feedback that decays quickly, but still gives about 7 or 8 audible repeats.

It also seems logical, although I can't quite see enough detail to corrorborate it, that each delay should have some slight time modulation added. I have no idea what shape the modulation should have... maybe random would suit realism, but I doubt that this early design would have had random generators doing this job... but I don't really know.

The main thing is to try and get your delay times as close as possible to this clip to get the overall sound and then tweak the 'colour' to taste. Again, I can't tell from the clip waveform if this is so, but I wouldn't be surprised if each audible repeat, or at least each delay module had different filter settings, to simulate reflections from different surfaces in the room (depending on the room you are trying to model).

Finally, not having heard this ambience 'at work', I must say that it's waveform doesn't look very accurate - With natural reflections, it is very unlikely that each reflection would have 'feedback', but I suppose that the audio world is full of things that should sound terrible or great, but actually have the opposite effect! Very Happy


Good luck!

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3phase



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PostPosted: Sun Aug 28, 2005 12:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

sheridan wrote:
I don't know much about recreating early reflections, but if I am reading this correctly, you are trying to get to the audio reflection pattern from the SPX audio clip...

To me, it looks like you need to use many more discreet echoes, each with much shorter delay times. Each should have feedback that decays quickly, but still gives about 7 or 8 audible repeats.

It also seems logical, although I can't quite see enough detail to corrorborate it, that each delay should have some slight time modulation added. I have no idea what shape the modulation should have... maybe random would suit realism, but I doubt that this early design would have had random generators doing this job... but I don't really know.

The main thing is to try and get your delay times as close as possible to this clip to get the overall sound and then tweak the 'colour' to taste. Again, I can't tell from the clip waveform if this is so, but I wouldn't be surprised if each audible repeat, or at least each delay module had different filter settings, to simulate reflections from different surfaces in the room (depending on the room you are trying to model).

Finally, not having heard this ambience 'at work', I must say that it's waveform doesn't look very accurate - With natural reflections, it is very unlikely that each reflection would have 'feedback', but I suppose that the audio world is full of things that should sound terrible or great, but actually have the opposite effect! Very Happy


Good luck!


I tried it to reproduce the delay patterns but this dont sounds even close...there is much more muschiness in the spx as just normal delays do...its rather a reverb room and even with low densitys its sounds smeared somehow.
To having acces to this kind of reverbcolours can create quite a bunch of intresting sounds on the G2 that the reverb module cant do...
All this gated and reverse snare stuff from the eightys is often based on theese dirty spx reflection clusters.
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3phase



Joined: Jul 27, 2004
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PostPosted: Wed Sep 14, 2005 8:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just started new tests..some results from the first test...
If somebody get any ideas please let me know...

I did the first test with the selfdefinable ER algorythm of the SPX 1000.
1 Tap... Diffusion and Liveness parameter seem to have no fx in a one tap setting...
I send a tone generator to the device and do frequencie sweeps with sin and saw signals
Two Oscilloscopes get compared ..one with the plain testsignal that triggers the other that shows the output of the spx.

1- sine wave passes uneffected on density 0 and 1 on the whole frequencie range. On 2 and 3 just little leveldrops that get more in the higher frequencies...seems to be only phase cancelations by the multiple sub delays.

2- density 0 looks like a plain delay but phase gets more altered during the frequencie sweep than with bypass.

3-Allpass filtering seems to be involved...phase of sine is constantly changing in relation to reference during a sweep thru the frequencie range
4- As higher the density as more phase change is going on during frequencie sweeps.

5-Density 1-3 get increasing more reverbish sound

6-A Sine wave passes the process un effected.

7- There are no indications of lfo modulations

8- A Saw wave gets altered by the process.

9- There are certain frequencies on the saw wave that pass the process with density 1 allmost unaltered.

10- These frequencies are 58, 116, 175, 233, 291, 350, 408, 466, 525, 583.. and so on... around + 58 hz. What is indicated by this?

11- On Density 2 and 3 the waveform looks also less chaotic on theese frequencies. with density 3 the "sweetspot" is some hz higher than with density 1

regards
Sven
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