Yeah, that works. I put on my peepers and I can read it! I'm going to assume that your miking reflects audibly flat and requires no compensation curve.
The blue line is probably close enough to flat as it is. Just a little bass boost and that would be fine... maybe a tiny little tweak in the sensitive octave of 3kHz to 6kHz. Above that, it doesn't matter as much. Those headphones probably sound pretty darn good with no EQ.
The green line would definitely benefit from equalization. You could pull back the whole range from upper mids to treble and it would be a lot more comfortable to listen to. You probably wouldn't be able to help the sub bass enough though. That is a big drop at 80Hz. You could certainly help above 40Hz, which is all that really matters for headphones though.
The magenta line is a bit more problematic. With all those spikes across the whole bass to midrange, and that huge rise right up to the most sensitive part of human hearing, I don't think those cans could be tamed. They could be helped, but they would never really sound very good. I doubt you could pull the bass all the way up. You would have to push the top end down to meet it. That would reduce the volume considerably, because that is a 45dB imbalance. What a mess that is!
I mainly wanted to show that different headphones have very different frequency responses, and that the responses are far from ideal.
Sorry I didn't clarify the data a bit more. I will refer to post #53 that you replied to, since I changed the colors from my previous post.
Also, I did take RMAA measurements of the Onkyo SE-90PCI that drove the the headphones for these measurements. It measures very flat, I can post the RMAA charts if you like. The mic itself is the Dayton EMM-6 from Cross Spectrum labs and includes a calibration curve for 5 Hz to 25 kHz that is indeed used for these measurements.
Blue line:
Beyerdynamic DT990 Pro open back headphones. The bass response will be the best on these with my measurement scenario because it is a larger driver that is pretty close to the mic. I was able to match 1kHz @ 75db for the DT990 Pro, but the other responses were so weird in comparison, that I wasn't sure where to set the input sensitivity. I thought that 1kHz might be a good place to start, but it looks like there is "room" gain effects at 1kHz when looking at the chart for the other headphones in the chart. I set the input sensitivity to keep the peak level below 90db. This is just a bit below the peak level the
T990 Pro.
Green line:
Yuin PK3 earbuds. The bass response has a roll off since they are just earbuds and the bass driver is very small. The bass when wearing these is actually pretty great until you get to maybe 40 Hz, subjectively. I would say these earbuds sound very good overall, and only really lack in the low bass region.
Magenta line:
Some cheapo JVC earbuds. They only have a respectable bass response when there is a seal with the ear. The mic is 1cm away, so the squiggles in the bass region is actually the noise floor of the room I measured in at the mic location. The noise floor was only only about 35db - 40db above the recording reference level (75db @ 1kHz) The bass rolls off into the noise floor around 500 Hz and below. The JVC earbuds are actually rather bassy if jammed into the ear properly. These earbuds sound good with major EQ. The bass sounds satisfying, but without EQing the mids and the highs, they sound very harsh and cause fatigue.
I have thought about trying to construct an ear canal shaped measuring apparatus to get a more realistic bass response (since I'll be getting some custom IEMs, I'll have some molds to play with), although I expect that to be quite the undertaking.
The charts do show with good accuracy the response with the mic 1cm away in free air. I know that it will get very complex when accounting for human hearing, ear shape, seal, etc.