How to use the all-pass filter?

[_al_]

Allpass filters are used to manipulate the phase of the signal.
http://www.uaudio.com/blog/allpass-filters/

Interesting read.

But I don't here a difference

What's the secret? I want to have pro ears, I want to hear the difference. Can you give me a hint on what to listen for?

Listen on headphones. Should be more obvious there.
My bass busses are VERY sensitive to phase shifting, but maybe going through multiple multiband devices amplifies it somewhat. Not sure.