Maximum Impact?!

Yeah, it's a really effective and convenient piece of kit. The only hardware solution I've come across that you can see and control the EQ on the unit itself. I find the controls faster and more precise to use than software solutions. The other hardware equalizers seem to need a PC with propriety software to control, and cost 3-5x the price.

For those that way inclined you can use the stereo widening function as a rudimentary crossfeed, minus the proper timing delays.

Equalisation is also a great investigative tool, educational even. My experience trying to EQ the HD800 and TH900 did not go as well as I expected at the beginning of my attempts. Simply matching to the Harman Target as based on @Tyll Hertsens measurement head does not produce good results at all, but it's a useful place to start. The HD800 can't be helped much in the bass area, it's quantity goes up but it still hits with a whimper. Where it comes to the TH900 what has worked well is reducing the bass-mids bleed plus the 6khz peak with a fairly wide Q, and taking down the overall brightness. At times vocals can sound a bit distant and trying to EQ up the measured dips within the mids hasn't worked out well, so I've had to let them be and accept them as they are.

In line with what @Marvey said EQ worked the best with the HD650, it was by far the easiest. Because you're not putting out any fires, just gently molding an already consistant frequency response. A bump at 3.5khz and increase in the treble frequencies to get it closer to the HD600, with some sub-bass enhancement and it's the best in tone I've ever heard from a headphone.

 

@Marvey that like is for the DEQ2496, not java. Have you used the behringer with analog in? I am curious whether you would recommend it for applications where AES isn't available and toslink is the pits.

 

On the topic of EQ:

Spoiler: EQ/Measurement rant

I think a lot of this experience comes from trusting headphone measurements as a baseline for EQ. Trusting flat plate coupler measurements is generally a bad idea, especially with headphones designed around the shape of our ears, such as the HD800. If anything the measurements on CS really showed that the metal mesh doesn't cause the 6kHz peak on most flat plate couplers.
Dummy head data is entirely useless as long as we don't have a proper compensation curve. Now everyone could go out and make their own curve for common dummy heads (like Tyll's), but it's not easy. The curves we currently have I feel are weird and I think it would be hard to come up with a real compensation curve, because what do you use as a reference? Speakers aren't that good of an idea because there is no reference for perfect neutrality in speakers. Even if you had a speaker that measured super awesome, once you put the dummy head into the equation it all goes to shit. Position the speakers differently and it'll measure (and sound) very differently. Put them in a different room and you'll get very different results. And then I don't even think headphone and speaker FR measurements are comparable in any way because it's just such a different sound field. A FR measured with a dummy head for speakers is not the same as that measurement for headphones.
Measurements with mics in your ears, but not at the eardrum level can give you some insights into areas where other measurements fail, but they fail catastrophically in other areas. Listening to sweeps and pink noise can also give you some indication, but everyone has their own reference here. How do you know how it's supposed to sound?

Now, what I'm really saying here is that the 6kHz peak and 4kHz dip as measured on almost all flat plate coupler measurements on a stock HD800 is largely a measurement artifact. It's been a long time since I ever listened to a stock HD800, but with the HD800S I don't hear a 4kHz dip and I also don't hear a 6kHz peak. I actually never heard a 6kHz peak in the first place and the HD800S has a huge dip there that causes it to sound really odd in the treble. I heard two huge 5 and 7kHz peaks, but 6kHz was flat to my ears (very likely not the same for others). The upper midrange is dipped, but not at 4kHz. EQing based on flat plate coupler measurements just makes it sound even more screwy.
That's not to say that I think you can EQ a stock HD800 to neutrality. Precise mods can get you much closer than any surgical EQ.

Hmm. I didn't like the adapter. My main issue was a 2kHz peak and the adapter just made it worse. For reference, here are my measurements:
http://www.superbestaudiofriends.or...easurements-by-serious.2518/page-2#post-72682


As others have said, to me EQ can't fix the things that make me really want to listen to music. EQ can never get rid of an unnatural Beryllium-tweeter-extended-as-widebander coloration. EQ won't make my HD800 (already a very lively sounding headphone) sound as lively as my OB speakers with the Voxativ drivers.