DSP Robotics Support

I do phaser using this scheme (found on the wiki)
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Phaser_feedback.svg/600px-Phaser_feedback.svg.png
but I want to reduce the distance between resonances, can not figure out how to do it.
Now able to increase the distance but can not reduce.
I think I need another filter, but do not know why

found the solution, need to use a filter with resonance

Yes, you need second order (biquad) allpass filters for that. Get RBJ filters.