How to get constant amplitude and constant velocity volume curve straight

Hi everyone, 

I am trying to understand my turntable’s frequency response and to this end I have a sweep from the CBS STR 100 record.

The sweep (for each channel) is constant amplitude below 500 Hz and constant velocity above that. I am trying to find a way to spot the gaps in the frequency response but on the volume curve there is a line rising up to 500 Hz and descending after that (as it should!). How could I tell Adobe Audition to show me the exact frequency response curve please? Is it even possible?

Thank you!