I checked the actual response of my x'over w/ REW and it goes -3db from 30 to 20 hz and -10db from 20 to 10hz ..
They are not budget drivers. Low prices today are only the result of it not being a currently manufactured product for several years; either you are buying used or marked down clearance items. And when they were a current product, the 12.1 sold in car audio shops for about $220-$240 each. Even at that price, they are constructed/ built superior to most drivers costing more. In case you did not notice, the motors on the Kappa Perfects are entirely machined, not just cheap low tolerance cast parts. They are still an extremely high SQ woofer today; the only issue is the one I specified earlier in regards to mechanical failure without warning, since they don't give much in the way of warning with reduced SQ or distortion when driven hard, which is not usual, as most drivers start to make all sorts of obvious distortion, etc. when driven even moderately hard, giving the user a clear tip to reduce the level a bit.
First, xmax is an expression of where the motor is at a certain percentage of motor and suspension non-linearity. Mechanical excursion is farther away, and in the case of these drivers, much farther (around 10 mm one way more excursion before hitting mechanical limit). Of course, on some questionable quality drivers, the manufacturer may actually use mechanical limit as the stated x-max. And x-max is not consistently reported between all manufacturers. Infinity is very conservative with the rating on the Kappa Perfect drivers, however. The VQ appears to have a more robust suspension to keep the motor from failure excursion rates based on reported failure history. Keep in mind, the Kappa Perfect drivers were intended and are for absolute sound quality applications. They were never intended to win SPL contests.
