There is such a thing as a "flat response" for headphones, it's called a room-curve compensated diffuse field target curve. More on that here

The problem :

1. It's super hard for headphones to achieve this target, too much auricle reflections happening between the drivers and your ears.
2. Those reflections depend on your own ear. Measurements rigs used by Sonarworks will never be able to pick that up.
3. Some headphones have huge unit-to-unit variations (*kof* Audeze *kof*), so even for imbalances not caused by auricle reflections, the average curve from Sonarworks will not always correct them (sometimes, it can even make it worse).
4. The only solution to get a 100% "flat" sounding headphones is to measure them on your head with probe mics placed in your ear. Good luck with that.

Sonarworks can improve your headphones a bit, but it's never gonna be perfect. However, it's not that big of deal, because if you learn how music sounds on your headphones, you will learn how to mix on them. Still, I think that it's always a good thing to have a neutral sounding reference device. Think of it like screen monitors for color graders. You can watch a hundred movies on a "bad" screen, with wrong colors, and you could learn to properly color grade on it. However, why would you not want a calibrated screen in the first place ?

If you're looking for true and perfect neutrality, you have to use speakers in a good room, or IEMs, as they don't suffer from auricle reflections, just pressure issues inside the ear canal (and pressure issues can be EQd, unlike reflections).

 

Last edited: Sep 15, 2023

Which is why to achieve the best possible outcome one needs headphones calibrated by Sonarworks. I find the default (averaged) profiles to be slight improvements (more so with certain models) but the difference is night and day with actual calibrated headphones.

 

My 650HDs lacks a lot of punch on the lows so the Sonarworks curve help me a LOT not to overshoot them while mixing. I'm using the average profile that R2R gave us some time ago and it's a huge difference over not doing it. I whish I had a truly legit personlized profile but hey, too lazy and afraid of sending my canes over there to get one. I'm a hobbiest so the average works great too XD.