What Exactly does the Stereo Widener do?

Typically a "Stereo Widener" simply inverts the phase of one channel (Left or Right)

It's the "Awesome" switch for your Kemper.

Well, 01000100 told us "it's a different kind of stereo widener, that doesn't mess with the phase and remains competely mono-compatible"

Quote from fretboardminer

Well, 01000100 told us "it's a different kind of stereo widener, that doesn't mess with the phase and remains competely mono-compatible"

Strange....I can't hear a difference with one FRFR powered monitor

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Strange....I can't hear a difference with one FRFR powered monitor

Well - that confirms the KPA "Stereo Widener" is NOT simply inverting the phase of one channel (Left or Right)

From the manual:

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Not an equalizer in the traditional sense, but it does use equalisation to work its magic. By emphasizing certain frequencies on one stereo side, while attenuating them on the other, it creates a subtle stereo ef- fect. This is done symmetrically, so that when the signal is summed to mono, the effect is completely can- celed out with no coloration to the sound.

It sounds like a pair of matched EQ stages which sum to 1. Imagine separate graphic EQs for left and right where the boosts in on channel are perfectly matched with a cut in the other so the sum is unity gain.

It makes sound 3D.

I've just gotta get mine running in stereo ...

Once you add just a touch of reverb, it's difficult to notice a big difference with the widener on/off.