Here is a video, a drawing and a description to help you understand the MAM operation better:
Video: http://youtu.be/LqsFELUW-mc
Operation:
1. All the way out CLOSES the ambient port, thereby defeating the ADEL membrane as it can't move because it can't compress the air trapped behind it.
2. All the way IN opens the ambient port completely, but ALSO tensions the membrane - which increases the bass response under open ambient conditions.
3. Halfway between these extremes, the membrane is most compliant (floppy) because the ambient port is fully open and the tensioning apparatus is not engaged at all. This position mitigates pneumatic pressures most effectively, but the bass may seem lacking at first until your ears have a chance to relax (up to 10 minutes). The bass should then become much fuller and faster, because the unnatural resonances of your sealed ear canal and in-ear pneumatic pressures have been mitigated.
If the bass is still lacking after full relaxation, try adjusting the MAMs slowly in or out to suit your taste, but without fully closing them (moving them all the way out), as this can trigger your acoustic reflex, thereby possibly making it necessary for you to allow your ears to relax again.
The extreme positions, 1. all the way OUT (closed) and 2. all the way IN (open, but tensioned) may sound similar because these both impinge more pneumatic pressure on the ear drum due to the fact that the ADEL membrane is immobilized by 1. Static air pressure (all the way OUT or CLOSED) or 2. Mechanical tensioning (all the way IN, or OPEN BUT TENSIONED).
The "right" ADEL adjustment will be somewhere between these two extremes, depending on how much pressure is retained in your middle ear, your listening preferences, the altitude you are listening at, whether your are exercising or running while listening, the kind of music you are listening to and the conditions under which it was recorded. Both extremes of fully out (closed) and fully in (open with tensioned membrane) are often useful under demanding exercise or listening conditions or varying ear anatomies.
Hope this helps; please don't hesitate to contact myself or support@64audio.com if you need help.
Stephen Ambrose
Founder, Chief Scientist, Asius Technologies
Inventor of the In Ear Monitors and ADEL Technologies
Email: Stephen.Ambrose@AsiusTechnologies.com