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Stereo expander not 100% accurate? UPDATED


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#1 ffx

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Posted 02 August 2017 - 13:10

If you setup these two three stereo expanders at the very last position in the master chain:

Bildschirmfoto 2017-08-02 um 15.16.33.PNG

 

You still will get some signal in the master output in the low area:

Bildschirmfoto 2017-08-02 um 14.10.12.PNG

 

Description to above expanders: First one removes side signal, second one rotates the signal by 180 90 degrees (or should at least, we want to have a perfect side-only signal), third again removes side. 

 

Expected result: 100% silence

 

Actual result: Some quiet low end, maybe resulting in rounding errors in the "Surround" parameter?

 

 

Discovered by joule.

 

 

EDIT:

Fixed image / description.


Edited by ffx, 04 August 2017 - 15:43.

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#2 OopsIFly

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Posted 02 August 2017 - 15:00

the residue bass seems to come from the surround parm, I replaced the surround effect with a gainer inverting only one channel of a mono sound, then collapsing to mono after it seems to cancel 100%.

 

I dunno, surround was never advertised as pure side side signal generation, maybe it works differently and treats the bass some special way, because, eh...? Render your setup & boost it and you will see it is the low end from whatever stuff was put through.


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#3 ffx

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Posted 02 August 2017 - 15:35

OopslFly, using gainer is a great idea! Damn :)

 

I think "surround" is just phase rotation. at 100% it should do 180 degrees.  That slider is very old, from the times before Renoise attempted to sound professional, I believe. Could the devs give me a statement, is it (a bit buggy?) phase rotation, or does it do more than that.


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#4 joule

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Posted 02 August 2017 - 16:58

It's not only bass content. There is also some attack part of the normal sound getting thru.

 

It's negligible sound wise, but maybe it reveals something fishy going on in the signal path?