Im still new to reading data sheets like these. Could you enlighten us a bit with what is going on here? also, i was also confused about the crossover. I had the bass boost on with crossover at 80hz, which is default. I just want to know what is this crossover?
Use EQ to get a Flat Frequency Reponse:
http://en.wikipedia.org/wiki/Graphic_equalizer
http://www.soundonsound.com/sos/1995_articles/mar95/eq.html
http://www.audio-production-tips.com/graphic-equalizer.html
http://www.presonus.com/community/Learn/Equalizer-Terms-and-Tips
The Reference point/calibration of reproduction/recording/processing of audiosignals is a flat frequency response at 0 dB from bandwidth 20Hz to 20kHz, means the audiofreq. is as close to the original LIVE signal without alternation.
Since that is not possible with reallife audio gears, they use the EQ to equalize/correction to reproduce the flat freq. response.
With the graphic Freq.Response data sheet of your headphone you can try to equalize to the closed corresponding EQ frequencies to apply the correction.
It's a logaritmic scale each line represent next decimals up: 10Hz 20Hz...90Hz 100Hz 200Hz...900Hz 1000Hz 2000Hz...etc.
In theory supposed the presented graphic FR is from your actual headphone (in reallife they use feedback microphones/dummy head http://en.wikipedia.org/wiki/Dummy_head_recording to get the graphic FR scale when playing the some bandwidth Freq. sweep tones through) and with the EQ you apply the correcting x dB to the tops and bottoms close to the ideal 0dB FR line.
Correction to the X1 FR would be: 31Hz +5dB, 62Hz +2dB, 125Hz +4dB, 250Hz +7dB, 500Hz +8dB, 1kHz +10dB, 2kHz +12dB, 4kHz +15dB, 8kHz +11dB, 16kHz +24dB.
Thats the theory, in practise year ears decides if you like it or not.
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In theory the bass (subwoofer) booster LPF (Low Pass Filter) is for the subwoofer output but here you can use it as 1 band parametric booster with the cutoff Crossover Frequency adjustable from 10Hz to 1kHz.
For (your) headphones going lower than 62Hz-ish is useless because of high THD% Total Harmonic Distortion and eventually will blowup/damage the small headphone's drivers if volume is set too high!
But if you insist the Crossover freq. would be set to 15Hz with 10% to 50% but doesn't make sense and waste of energy and damage since you almost cant hear it and headphone drivers gets distorted!
Bass Subwoofer Crossover Frequency:
http://www.audioholics.com/subwoofer-setup/setting-the-subwoofer-lfe-crossover-for-best-performance
http://www.ramsdellproaudio.com/support/sub_crossover_pt.htm
http://www.soundandvision.com/content/where-should-i-set-my-subwoofer-crossover
http://www.wikihow.com/Use-a-Parametric-Equalizer
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As for THX surround setting, its just simulate virtually the global 5.1/7.1 speakers setup from a hometheater with adjustable surround 0-100% distance/volume between the speakers to your headphones/ears.
Suppose surround at 0% the speakers(or only FL/FR is active) are at maybe virtual 6 metres distance and at 100% would mean they are maybe 0.2 m closer.
Depends on variable contents and its effects, I'd set for Stereo source from 10% to 40%, for 5.1/7.1 movies from 40% to 60% and for 5.1/7.1 games from 40% up to 80%.
THX surround is much better than DH with its exaggerated reverberation.
