A couple years ago I bought a pair of Audeze LCD-2 headphones. I’ve listened to many headphones over the years and they are the best headphones I’ve ever heard. This is what I had to say about them.
But, like all things created by mankind, they’re not perfect. Their near-perfect frequency response has a small dip between 2 kHz and 9 kHz. It’s linear and smooth, so subjectively is barely noticeable. Yet it slightly subdues the sound, as if you’re sitting a few rows back from the 1st row.
Since I recently got a digital signal processor, I figured I’d try it out on the headphones. I put a single parametric EQ, +3 dB, centered at 4,600 Hz, 2 octaves wide (slope 3 dB / octave, or Q=0.67), so it has effect between 2,300 and 9,200 Hz. To my ears, this made the LCD-2 absolutely perfect. It’s subtle yet definitely noticeable (I blind tested it on a variety of recordings), and shifts you back to the 1st row of the audience.
I tried +4 dB and it was good, though a bit more than needed. +2 was not quite enough; +3 was perfect. And I tried shifting the frequency up and down a bit, but 4,600 Hz sounded perfect.
From what I can see in specs, this makes the LCD-2 sound closer to the LCD-X, taking it from slightly warm or rounded, to neutral. The LCD-2 still sounds yummy, yet realistic – yet now it’s a touch more detailed. This EQ doesn’t change the character of the sound, it just makes that dip shallower giving a bit more upper midrange and treble detail. It’s about as close to perfect sound as human engineering can achieve in a headphone.
I’ve considered getting the LCD-X but this change nixed that entirely, making the LCD-2F near enough perfection to keep for a long time.