The "feedback" is the true heart of a cutting system:
It avoids all undesirable resonances across the audible spectrum, stabilizes the head and works as an electronic damper, improving stereo separation, reducing the natural distortions and making the frequency response flat.  It works so: a little part of the main signal is out-of-phase mixed with the monitor signal taken by 2 additional tiny fragile coils positioned in the axis of the main driver power coils; doing so, the effect of a subtraction of all undesired resonanced was obtained. This is extremely important in a cutterhead to obtain a wide flat frequency spectrum, low distortion and a self-transient control of the overall system.  There are examples of cutters that works well with oil or gum damper systems, but the best remains however the feedback electronic control, which was adopted by practically all cutterheads of all producers.
 

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