Neutrality is a fiction. And it is primarily a fiction because we are dealing with so many complex distortion mechanisms within the recording and playback chain. The reason that there are so many systems and so many components is that we are all matching the distortion type and spectra to a paradigm of music that we have in our head.
If we have two identical systems and one has 3% second harmonic distortion, decreasing linearly with each harmonic out to the 7th and another system with .1% second harmonic distortion .3% third, .1% 4th, .9% 5th, .2% 6th and 1.2% 7th, which is the more "neutral" neutral reproducer. The first has a very linear distortion spectra yet the second has much lower aggregate distortion. I would posit that some of us would find each system more "neutral".
More often than not, I find the concept of neutrality in audio reproduction to be a cloak that justifies buying decisions by the insecure.
Which brings us to fidelity to the source. And if the source is live music in the studio it could be that the el cheapo op amps and miles of wire used in the recording process add odd order harmonics, bleaching the sound. And here comes Johnny Audiophile with his single ended amp that adds second harmonic distortion. Well the amp may be rebalancing the harmonic envelope in some crude way that actually makes the aggregate system of recording and playback closer to the sound in the studio than if a more "neutral" amp was used. This whole concept is a loser's game IMHO.
If we have two identical systems and one has 3% second harmonic distortion, decreasing linearly with each harmonic out to the 7th and another system with .1% second harmonic distortion .3% third, .1% 4th, .9% 5th, .2% 6th and 1.2% 7th, which is the more "neutral" neutral reproducer. The first has a very linear distortion spectra yet the second has much lower aggregate distortion. I would posit that some of us would find each system more "neutral".
More often than not, I find the concept of neutrality in audio reproduction to be a cloak that justifies buying decisions by the insecure.
Which brings us to fidelity to the source. And if the source is live music in the studio it could be that the el cheapo op amps and miles of wire used in the recording process add odd order harmonics, bleaching the sound. And here comes Johnny Audiophile with his single ended amp that adds second harmonic distortion. Well the amp may be rebalancing the harmonic envelope in some crude way that actually makes the aggregate system of recording and playback closer to the sound in the studio than if a more "neutral" amp was used. This whole concept is a loser's game IMHO.

