Argyro you are refering to the transparency of a system and not the speakers. This is like comparing apples to oranges.
A speaker can be perfectly netural even though its output differs from the source material because it could be the electronics preceding the speakers responsible for this differance.
No matter how much the electronics preceding the speaker in the system is polutes the neutrality of the source material, it is still possible that the speakers can be very neutral. So it is only the input to the speaker from the amplifier driving the speaker which is the measuring stick for the transparency of the the output from the speakers. If what comes out of the speaker is the same as what is sent into it, it is netural. That is all.
PERIOD!