Response curve for Live Send Pot?

Mar 5, 2012 at 9:39am

Response curve for Live Send Pot?

Hi all,

does anyone have information regarding the send pots in Ableton Live?

I’m trying to build an equal-power panning system for an 8-channel application and have found that the send pot is not truly logarithmic. In fact, it looks like it’s modelled on a “real life” log pot.

Does anyone know what function Ableton use to produce this response?

best wishes

richard

#62158
May 16, 2012 at 10:18am

OK. In case this is of use to others, I’m going to answer my own question:

The Live Send pot is neither linear nor truly logarithmic.

This is of particular importance if you are using it for an equal-power application like panning. Multichannel spatialisation devices like [Max Api SendsXnodes] and [Max Api SendsPan] that control Live Sends via the API and do not address this issue produce a marked drop off in level when sounds are panned in-between speakers in multichannel environment.

I talked to Ableton who say the design is procedural and not given to a mathematical solution, so I did some measurements and produced a lookup table (antipot.aif) to make the necessary corrections.

Here is the .aif file and a small example patch.

I have also applied this technique to a couple of audio-rate M4L devices which I will put up online soon.

best wishes

Richard

Attachments:
  1. antipot.aif
#224499
May 16, 2012 at 3:43pm

Hi Richard,

I ran into this exact same issue earlier this week trying to implement equal power quad panning in Live. It drove me nuts for a while because all the sources and tutorials I found online claiming to do this seemed to get it wrong.

I ended up using the curve~ subpatcher from the Max Api SendsPan device. If I remember correctly a value of about 0.83 gave me – 3db between speakers.

Thijs

#224500
Jan 5, 2013 at 7:12am

So happy to see someone has looked into this. Thanks fellas.

#224501

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