Your link is completely unhelpful. What is the source? Who knows where this came from and how it was made.
Not to mention the abysmal visual fidelity - the axes aren't even labeled. I can barely even tell what I am looking at.
My point being, you might hear it as being overly bright, but the vast majority of people who use it do not. It's been a professional gold standard for decades. It has thousands upon thousands of glowing reviews. And with an E17K, it doesn't even matter if the OP finds it too bright out of the box - they can change the frequency response at will.
Original source:
http://www.innerfidelity.com/images/StaxSR207EP507LeatherPadsSerNumSB22217.pdf
http://www.innerfidelity.com/images/StaxSR207SB2217.pdf
Unfortunately, Tyll at InnerFidelity did not measure the 7506, but he did measure the V6, which is similar, but warmer and not as bright. (I owned both.)
http://www.innerfidelity.com/images/SonyMDRV6.pdf
I think more people think it's bright than those who do not. I've talked to a lot of audiophiles and done tons of research. The fact that it is a popular studio headphone is meaningless, because all sorts of bright, warm, dark, etc. headphones are used in studios. That has more to do with marketing (and various uses for headphones in studios) than anything.
https://www.google.com/#safe=off&q=%22mdr-7506%22+%22bright%22
Over 161,000 results relating to its brightness, and that's just using one set of keywords.
I'm genuinely confused how you don't hear the nasty treble peaks. I mean, it's wayyy brighter than STAX. It literally sounds like someone took an equalizer and increased some of the treble frequencies to levels that cause pain. It's always possible that mine was defective or counterfeit, but it doesn't seem likely.