For an open dynamic, the bass is up to par with anything else. A +2 boost in eq around 60 hz does the job for me. They handle EQ very well.
As for the treble... I have seen two completely different measurement curves for it, one which shows elevated treble and one which does not. It's important to take various measurement sites with a grain of salt, because many of them don't post their setup, and any site that sets out to make a hitpiece (Verum Sonus) can use whatever combination of sources they please to get the terrible looking measurements they want, to confirm their bias. Suffice to say, these headphones have a slight treble raise, but the emphasis is on 'slight'. It is high quality treble which I do not perceive as remotely grainy, so I do not mind. The SHP9500s will sound on-point from warmer setups. I've managed to replicate both of these frequency curves below on different dac/amps.
https://diyaudioheaven.wordpress.com/headphones/measurements/brands-philips/shp9500/ - murdertreble. this tends to occur on poorly synergized dac/amp combos
https://www.rtings.com/headphones/reviews/philips/shp9500-hifi-precision-stereo - dead neutral. this is how they sound on my phone, as well as most integrated dac/amps.
I agree that the bass is pretty decent, and does compare favourably to some other open backs. But there are others that have more bass.
When I ordered them I was expecting them to have less bass than, it turns out, they actually had.I also agree the bass can be boosted nicely with eq, if one so desires.
I have seen both the graphs that you linked to, and I agree entirely with you, that It's not possible to compare graphs from different sources. Sometimes though, I will compare different graphs to see if they have anything in common in a general way. The diy graph and the ratings graph don't have anything in common,from what I can see.This isn't too surprising. Rtings uses the hats dummy head , diy doesn't. Also, diy doesn't use a compensation curve. Ratings plots the frequency response of the headphone relative to their target curve, which is the flat dotted blue line.
Interesting, to me,was the graph at golden ears headphone reviews. Below 1khz. there was not much in common with the rtings curve , but from 1khz. to 10 khz., ignoring the graph, and just looking at the general shape of the curve, it was quite similar to the ratings curve.
I still don't think the treble is exactly neutral. It is not as extremely elevated as the diy curve makes it look, but from about 3khz. to 6khz., on rtings graph there is some elevation. And, of course, as with most headphone responses I've seen, there's a 10khz. spike.
I also own the Senn. hd598. When I first got the shp9500s, it was the only headphone I listened to for 5 days. After that I pulled out my 598's . I heard the 598's as warmer with less brightness and not as detailed in the treble. I looked at rtings comparison page, where you can overlay the frequency response of two headphones.This is an apples to apples comparison, since the same equipment, procedure,compensation etc.are used to measure different headphones.
The graph shows the 598's to have a little more energy from 100 Hz. to 500hz. From 100hz. down to 20 Hz.,the response for both headphones is identical.From 500hz. to about 4.5 khz. the response is fairly similar. Not identical, but similar. From 4.5 khz. to 8khz. the response deviates, the most..The 9500s has more treble energy here.A maximum of 5db at 5.5 khz.
This could relate to why I heard the 598's as warmer, and less bright , with less detail.
This isn't meant to imply that the 598's are better, or worse than the 9500's. Just that the 9500s are brighter. Of course one could say, the 598's are recessed in the treble,and the shp 9500s are neutral.
As I've said before on this thread; for what I paid for the 9500s; they were, and still are, a bargain.