True-Fi by Sonarworks - Studio Sound on Your Headphones.
True-Fi by Sonarworks eliminates the inaccuracy of consumer headphone collaboration through an algorithm to flatten the sound, producing the "True-Fi" studio sound originally intended by the artist and producer.
Hard to believe that this exists, right? Try the free trial on the website and subscribe for Mac and/or PC for just $79.
Sonarworks True-Fi - Your Headphones, Studio Sound
True-Fi makes my crappy, five year old wireless Sony headphones sound *almost* as good as my open-backed Sennheisers. It's not cheap, and it's not perfect, but if you regularly listen through headphones, it can make a huge difference in sound quality and overall experience.