I contacted Tonebooster and he deconstructs the argument that a headphone should have a flat response.
Now I was very intrigued.

Here is the conversation:
 
"Unfortunately it's not really possible to compare graphs between different measurement protocols. Firstly, the measurements you point to are 'blocked ear canal' measurements, while Morphit takes the effect of the ear canal into account (e.g. we are using open-ear canal measurements). As a result, measurements will look very different.

 
But more importantly: headphones should never be tuned flat, which seems the underlying assumption of the measurements you linked to. Have a look at the published work done by ourselves and for example Sean Olive from Harman:
 
https://asa.scitation.org/doi/10.1121/1.4984044
 
The ideal headphone response is not flat, but instead equal to that of a flat loudspeaker in a well-treated room. If you have a look at the paper linked above, you'll see that headphones are virtually never flat - intentionally so! The response of a flat loudspeaker in a room (at the level of the ear drum) will have quite some bass boost.  By using that as target curve, we ensure to have maximum consistency between headphones and loudspeaker playback, which is the primary goal of Morphit."
 
Then my new question:
 
"I'm not an expert, but at this link (http://reference-audio-analyzer.pro/stands.php) you can check all the measurement methods they used.Regardless of the considerations, there is a fact: my reference monitors (Tapco S5) always sounded with less bass than my headphone.
When I created an EQ manually, as you can see in this topic (http://forum.cakewalk.com/How-to-adjust-EQ-to-create-a-flat-response-for-headphones-m3686014.aspx), based on the graph I reported, the headphone basses decreased significantly, getting much closer to the reference monitor, unlike Morphit, which, as I had said, instead of softening the basses, made them even louder, thus getting even more different from my reference monitors.
I usually mix and master with headphones and then I'm amazed at your claim that headphones can not be flat. If so, what is the purpose of Morphit?"
 
And his new response:
 
"Like I said; have a look at the paper I've linked in my previous email, and have a read of Sean Olive's work (he has a lot of papers in the Audio Engineering Journal about headphone target curves). None of the preferred target curves is flat, in fact they are anything but flat!!
 
Morphit is all about consistency between headphones and loudspeakers. That means that the target curve of Morphit should be that of a flat loudspeaker in an acoustically well-treated room. As you can see in Sean's work, that response has quite some bass boost due to interaction of the flat loudspeaker and the reflections in the room. Hence at the level of the eardrum, there will be a considerable bass boost.
 
If we would tune a headphone flat, it would have insufficient bass compared to loudspeakers, hence inconsistent reproduction of timbre. This is one of the big shortcomings of all measurements reported on the site you linked to (and a greatly misunderstood issue in the audio engineering world).
 
That said: Morphit has all the tools to modify your target curve if you'd like to. It can even simulate a flat target at the ear drum (choose flat response as target curve for your headphones). If you do that experiment you'll quickly find out that a flat target curve is the wrong answer. Additionally you can customize the EQ as well by using the marametric EQ; feel free to reduce the bass levels in a personalized profile.
 
Last but not least: it could well be that the Philips headphone we used for measurement is different from yours. There could be relatively much bass in yours, or a leaky coupling between the headphones and our professional dummy head (worth 60.000!) causing a weak bass in the measurement. Unfortunately we've seen that headphones can vary quite a bit from one sample to the next for some brands.
 
Cheers,
Jeroen"
 
 

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Where is the truth?
 

+1 for SonarWorks here.  It definitely lessens the headphone effect for me.  I have the cheapes pair of headphones for mixing:
https://www.amazon.com/Superlux-681-Dynamic-Semi-Open-Headphones/dp/B002GHIPYI/ref=sr_1_1_sspa?ie=UTF8&qid=1511182645&sr=8-1-spons&keywords=Headphones+681&psc=1
 
SonarWorks has a curve for them!  They sound great using the curve.  VERY BOOMY without it.
 

My initial reaction to the first curve you posted was that those headphones should be fine without EQ. There are far more expensive headphones out there that don't look as good.
 
Yeh, we all hate seeing all those little hills and valleys, but in truth they are more trivial than they appear, and yours are easily within the window of what can be ear-trained away.
 
Looking at graphs, it's hard to make a distinction between significant anomalies versus inaudible variations. Valleys are less significant than peaks, and narrow valleys are often completely inaudible. But even setting aside the question of which of the bumps are important, flattening the response may still be a wild goose chase.
 
First, the assumption that "flat" is the ultimate ideal is predicated on a significant presumption: that your own hearing is flat. It isn't. 
 
Second, headphones should have a slight emphasis in the bass to compensate for the fact that they are so close to the ears. Unlike speakers that are 3-10 feet away, they don't get the acoustical assistance from the room that tends to boost bass. 
 
All that said, if I was applying EQ compensation for those cans, I'd be more concerned with the midrange dip between 1-2 KHz. Those are the most critical frequencies for mixing. I'd experiment with a modest (2-3 dB) boost there and leave the rest alone.