Yes, it is difficult to measure your headphones yourself. Fortunatety, most headphone frequency response curves (as well as several other useful metrics) are available online at
headphone.com.
"...if your headphones are so far out of whack that you have to compensate for them, then what you really need to do is start saving up for better cans." I should clarify that statement. My position is this:
all headphones are deficient and deceptive in some way, frequency response just being the most obvious shortcoming. It's an unavoidable consequence of sticking tiny speakers into tiny enclosures and jamming them up against your ears.
But by training your ears over time, especially by listening to well-made records on your studio headphones, your own brain can go a long way toward compensating for those limitations.
My everyday cans are ATH-M50s, and as you noted, they have a significant (~6dB) bass boost built in. If I hadn't been using the same headphones for many years, that could really screw up my perception and cause me to make bad EQ choices and mix decisions. But I subconsciously expect that hyped bass whenever I use them, and a mix won't sound right if it's not there. In the end that nonlinearity isn't so extreme as to be a problem.
Now, if I was stuck with Beats by Dre and that was my only reference, then I'd be in trouble. And I might have no choice but to resort to equalization to mitigate the problem.
In fact, I did create a Pro-Q preset at one time that compensated for that bass hype, as well as a couple other anomalies in the high end. But I stopped using it long ago because a) it was a hassle to remember to bypass it on exports and b) it didn't really make much difference anyway.
[P.S. Please
do argue with me, Paul. I do not take offense, and my favorite forum moments have been the times when somebody set me straight and I learned something in the process.]