[Audiophiliac]

I have used this on the HD800s and it has worked wonders

https://www.amazon.com/gp/product/B0BJVJ77SJ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

You will be messing around in the dark, until you are pleased with your sound. Sonarworks will do the same, only much more accurately with it's like 1000 or so EQ point adjustments made from measuring with a mic. But, you will have to use a pc. A hardware solution like that will work for any transport/source. But then, is that the best hw eq device? 5 knobs to turn, and one balanced one SE inputs? You can get more sliders, and then people say parametric eq is better than slider points.