It’s designed to be a linear device, which means it’s purpose is to get the signal from point A to point B with as little alteration as possible, all the while performing its duty.
The iEMatch adjusts levels while making sure the source impedance seen by the headphone is low and the load seen by the amplifier is within normal design parameters.
It does not alter (materially) impedances or affect the frequency response of the attached headphones.
It is not like some adapters sold that simply place a resistor in series with the headphone and often degrade sound quality.
In fact, the only measurable impedance swing on the iEMatch occurs when you switch it into ultra-sensitive mode. Even in this case, 3 ohms is nothing in the world of headphones.
Lastly, it has a measurably linear frequency response.
It’s not designed to ‘colour’ the sound in any specific way.
