How to equalize your headphones: advanced tutorial (in progress)

Then why do you target equal loudness curve in your equalization?

You use two EQs--an equal loudness curve (which can either be derived from loudspeakers or a generic curve) for equalizing your ears and a headphone tuning EQ for equalizaing your phones.  Your ears roll off in the bass (hears bass sounds to be quieter) so the equal loudness equalizes up the bass to compensate.  Then you can tune the headphone tuning EQ just by ear, by making all the sine tones sound equal in loudness.  If you omit the equal loudness EQ your resulting EQ will have way too much bass.
 
When you are done tuning the headphone tuning EQ, you remove the equal loudness EQ from the audio chain and have just the headphone tuning EQ in the chain for playback.

Got everything setup! Waiting for the tutorial for using the basic model for human hearing. I don't have a very good headphone for trusting it as reference! I hope I can make it as flat as possible using your tutorial
 

3. You don't have any setup you are currently satisfied with: download a generic equal loudness contour, EQ your phones according to the contour, then tweak the sound to taste, then when you are satisfied with the sound, create your equal loudness contour from your EQed headphones
 
Instructions:
 
http://www.mediafire.com/?rzzryhe139ivef1
 
Download this equal loudness curve and load it in a first Electri-Q EQ in VSTHost
Click M->Skin->Gain Range select 30dB to view the whole curve.
(You probably need to load the EQ file twice for it to load properly)
 
Then open a 2nd Electri-Q EQ after it like this

(The curve from the equal loudness EQ file should look like the curve in the middle, except the frequencies below 50Hz have been tuned down below the 0dB line to prevent clipping.  The other EQ should be flat to start with.
 
Then follow the following steps
1. Open Sinegen and set it to output to Line 1 (Virtual Audio Cable), the frequency to 1kHz and the level to -10dB.  Turn the windows master volume control and the volume knob on any amp you have way down for safety.
2. In VSTHost, click the "M" button to the lower right (on the blank EQ), set the Mode to Digital and Quality to Normal.
3. Hit the Power button on Sinegen and change the volume by changing the windows master volume and any amp volume controls you have until you hear the 1000Hz tone at a loudness comparable to the loudness you usually listen to music at.  Make a mental note of this loudness and a written note of all the computer settings associated with this loudness (ie Sinegen Level setting (-10dB), Electri-Q curve at 1kHz (currently -20dB), whatever the system volume is, wherever the volume knob on your amp (to your speakers) is set)
4. Move the frequency slider up and down (careful to avoid over-loud high frequencies, lower the Level if it's too loud) and check that the sine tones you hear are "pure" and that you don't hear "aliasing" between 10kHz and 20kHz (ie you should hear the pitch going higher and higher and then fading out; aliasing is where you hear a treble tone (still high but much lower than 10kHz) sweeping back and forth as you push the slider up from 10 to 20kHz).  If you have problems with this step report back to me and we need to troubleshoot sound settings.
5. If step 4 is ok, you can now start going up and down the frequency scale in Sinegen and make note of the loudness changes.  Go back to 1kHz at the reference volume you noted in step 3.  You can start fiddling with Electri-Q (on the blank EQ setting) immediately and hear the effect on the sine tones, but I prefer to leave Electri-Q alone first and adjust the Level and use the "+" (add record) and "-" (delete record) buttons to record the levels at different frequencies that correspond to the same loudness as -10dB at 1000Hz.  When I'm done I can "plot" the levels in Electri-Q and quickly make a rough equal loudness curve for the whole frequency range, like this:
http://www.head-fi.org/t/413900/how-to-equalize-your-headphones-a-tutorial/750#post_8208522
 
You should only EQ down to 50Hz, as the equal loudness curve has been shaved off below 50Hz.  If you want, you can equalize below 50Hz using this equal loudness curve
http://www.mediafire.com/?7b9olaa40qk4lfh
but it is hard to avoid clipping with this curve, not to mention that your headphones may be physically unable to produce a loud enough tone at those frequencies.
 
Safety notice: DO NOT try to equalize the high frequencies beyond the point where your hearing drops off.  A head-fier almost damaged his hearing with big blasts of supersonic frequencies he couldn't hear.
 
6. Some basic controls in Electri-Q: click on curve to add point, right click on point to change band type (most useful are Basic->Peak, Low Shelf, High Shelf, and Specials->Butterworth->LS/HS 24/48dB (allows a sharper low / high shelf than possible with the basic low/high shelf), double-left-click on point to change parameters: Frequency and Gain are self-explanatory, BW affects how sharply a Peak filter boosts or cuts a frequency and how sharply a low / high shelf filter transitions from the unboosted to the boosted frequencies.  As mentioned in the link above, right click on a point also gives you an option to bypass the point.  This is useful to compare the effect with and without a filter, or to do the plotting technique I write about in that link.
7. As you're adjusting the curve make sure to keep the curve centred on -20dB at 1kHz, otherwise your reference volume will change.  You can do this by moving the "Gain only" point up and down or adding a peak control point with wide bandwidth near 1kHz.
8. Click M->Presets->Export Preset to save your equal loudness curve.  (Remember to delete all the plot points first if you're using my plot method.  You can do this by switching to another preset then switching back (the up-down buttons at the bottom of Electri-Q next to the word "Presets".  Electri-Q doesn't remember bypassed points when you switch back to a preset.  A bug you can put to use in this case) Make a mental note of the rough shape of the curve, then switch to another preset and click M->Presets->Import Preset to load the preset you saved to a file.  Compare with the preset number currently holding the curve you just made to see if the curve saved and loaded properly.  There's a bug in the free edition where a preset may load with incorrect bandwidth for a point, causing the curve to change shape.  If this happens, find the point that has been loaded improperly, click it and press Delete on the keyboard to delete the point, and do M->->Presets->Import Preset again.  This should make the preset load properly.  If not, you may have to go back to the original Preset and export it again.  This is your new headphone EQ preset.
9. To test out your new EQ with actual music, remove the equal loudness EQ (the first EQ) from the signal chain.  Or, play music through a player that can host VST plugins itself and have it bypass VAC and VSTHost while loaded with Electri-Q and your new headphone EQ preset.  This can be useful if your VAC->VSTHost output is a bit glitchy, as mine was.
10. Tweak the EQ to taste with music.

Thank you, I just tried doing that, much better than just listening to Pink Noise.
 
Now I have another Challenge. Match the EQ curve of my Plot Points, it's almost impossible, wow! I guess I won't do them every 500Hz anymore!

... what phones are you doing this with?  It's better to start off with IEMs because those tend to have a smoother FR curve.

I have a Bose IE2, is that good enough?

Sure they are. As long as you're at it why not finish EQing the phones you've started on though (which are...?)

I have a Sony MDR-XD400 and I just bought a Corsair Vengeance 1300 Headset, not for music listening, but for using with my friends on Skype, and it has a good quality audio, so I was trying to EQ it the best way possible to use it for music too.
 
The second method of using VAC and VSTHost is amazing, you can change the EQ on the fly, I just have to learn how to shape Electri-Q curve to match the needs of the headphone, it's like 8000 0db then 8500 -5db 9000 -2.5db 9500 -2.7db 10000 -1db 10500 -7db
 
Like you said, if you change one point to match the EQ, all the curve gets changes and all your modifications are messed up

You have double clicked on a point and changed the BW to make the width of the peaks and dips fit the plot better haven't you?
 

I corrected a minor mistake in the guide for you, which resulted in removing step 3 from the previous version for a total of 10 steps.
 
BTW, it's more important to find the centre frequency of a peak or dip than to have lots and lots of plot points.  If you're experienced, after locating the frequency of the peak or dip by sweeping through frequencies in Sinegen you can shape the EQ to remove the peak / dip quickly by a single point with the appropriate bandwidth and maybe one or two points beside it to shape the frequencies around it somewhat, like the demo graph here at the end of the graph plotting tutorial post

I.e. the points at 5.4kHz, 8.1kHz and 12kHz (approx.) were set with appropriate bandwidth to give the right sharpness to the dips, then the points at 6.7kHz and 10kHz (approx) were added to adjust the height of the curve between those dips.  Those points had a wider bandwidth.

That's much smarter than what I was trying to do! I'm gonna try this today again with this new technique and I will let you know Gonna try for my IEM and also my other 2 headsets, although the Pink Noise can make your ears get tired really fast
 

You don't need to use pink noise anymore right?

I'm struggling to get stutter/pop free audio with VAC+VSThost when my PC is really busy (it's a very fast PC so it's not actually a performance issue). Other than that it works great and I'm glad I bought it. I've been messing around with buffer sizes and process priorities and got some success but I still can't say it's flawless

Have you tried elevating the priorities of the Windows audio services as described here?
 
http://www.head-fi.org/t/615417/how-to-equalize-your-headphones-advanced-tutorial-in-progress#post_8478930
 
I don't know what you're using it for but I'm just glad I can use it for watching movies. (I can use Electri-Q directly in foobar2000 so I don't need VAC for listening to music.)  If I were playing games or stuff like that I'd probably disable VAC or have the game output directly to the output sound device.