On Axis : 340hz - 92db, 16khz - 78 db
Off Axis : 340 hz - 86db, 16 khz - 75 db
Your ears, more or less would tell you the same thing. Numbers measured outside the car mean nothing, cause I'm hearing the speakers in the car. Try the test tones exercise. 800-8khz is the loudest in a car. Again thas for your and my older ears. For the young 'uns here maybe the roll off would start at 10. even for the 16khz would not be the loudest.
If you tried to balance out all the frequencies, so that they all sounded the same level, you would end up with the boom box sound. Or worse dull lifeless sound. When I had my sr's and things were dialed in well, the spl rose gradually from 50hz to 500hz. 50hz and 80hz though were way lower than 500hz.
The rise continues from 800-3khz. The sr's have a peak around the 800khz mark which needs a major cut. But the brightest frequencies in this range is 1.25-3khz.
With the tweeter gains set at -8db for left and right, the roll off starts around the 6khz mark. just for a lark if I set the tweet gains to 0/0, the roll off starts around 8khz, 12 is lower, 16khz is way lower. :)