The distortion curves shown are accurate, although pay attention that they are raised 20dB. If your speaker doesn't measure pretty much the same (within a few decibels), then something is wrong.
The JBL 2226 is an excellent driver, one of my all-time favorites. So don't leave 'em in that state, and don't settle for a shoddy recone job. Get the recones done right - by a genuine factory technician - and you will have speakers that are 100% as good as new.