Servo drive midrange?

[thadman]

I've seen several implementations of servo-drive technology (theres an article outlining it in this months Audio XPress) in subwoofers, but not midranges where we are most sensitive to distortion.

After reading up on these forums, I've come to the conclusion that most distortion from a driver is due to non-linearities in excursion (BL isnt flat).

From my understanding, the servo-drive units (measuring acceleration) apply different amounts of power throughout the stroke making its excursion more linear. Why hasnt this been done for midranges?

Is the active technology inept at responding fast enough in the midrange?

Would it be possible to create a *passive circuit* after measuring a driver (doesnt dayton offer a speaker measurement setup?) and its specific BL curve and applying power at the inverse of the curve (more power at the extremes) to make the BL more flat?

TC Sounds has introduced a *passive* answer to this solution by designing the voice coil around the BL curve (varied amount of windings)...why hasnt this been done on midranges?

[DanWiggins]

We redesigned the magnetics 5 years ago to create a flat BL curve, and have several midranges available with a flat BL curve.

To use a servo would require a VERY wide bandwidth on the servo circuit, and most likely would not be practical in terms of stability and gain-bandwidth product.

Dan Wiggins
Adire Audio

[nunayafb]

Probably due to the low excursion of mids, the cone moves less so the suspension is design for linearity over excursion, The motor geometry is simpler due to less excursion requirements-so a flat BL curve is easier to obtain than on a long throw woofer.