Not sure how and why such debates are on going.
The debates have been going on for decades and will continue to do so for decades and the reason is simple.
Human perception which is NOT a measurement device but people believe it to be just that and even claim they can hear more than what can be shown by measurements.
This is true for virtually all things in life and not just audio.
As from personal or objective point, there is no gear that DOESN'T influnce nor color the sound.
From a personal and objective point there is no transducer and acoustics as well as hearing/brain that does NOT influence the sound.
It appears that you also like to include re-production electronics.
Yes, some electronics can do that, some are purpose made, some 'change' waveforms deliberately (sound processors, tone controls) some by design.
Also all electronics alter (or reproduce) signals with some errors or additions but need to pass audibility thresholds of the listener in question.
The latter seems to be a matter of debate. Fact is that most aspects have been researched and that research shows there are tolerance bands around the 'known' threshold levels. These are smaller than some people believe it is.
One would impose certain harmonics in and the other would remove even what is existing in a source etc..
Sure you can add harmonic distortion to a single tone. When you do that with multiple tones you also get intermodulation distortion and there is nothing 'nice' about that.
For music you thus can add harmonics but NOT without also adding IM distortion so adding harmonics
only does not exist.
Since I'm personally part of this game I'm really sick and tired in neverending debates between who is RIGHT or who is WRONG.
I reckon you are being sick and tired being told you are wrong while thinking you are right which might or might not be the case depending on perception.
Everyone can measure and bounce to the results but NONE will give you the REALITY and HOW IT SHOULD SOUND LIKE as there is NO REFERENCE you can bound to.
You CAN have a reference and objectively show results because there can be a reference (in most cases) but it usually is difficult to do and time consuming as well as exhausting.
The measurements are only relative tho what EXACTLY?
To measured waveform fidelity IF measured correctly. Here the word 'correctly' is the difficult part. The second hurdle is the interpretation of measurements and understanding what results of various measurements mean AND you need to know about perception.
IF someone knows this pelase share but don't commnet for no reason trying to be smart in front of the audience.
Many people know this, even more people think they know it but do not known enough. There are also people who (think) they know more.
The problem here is perception and bias of the one that is being told/explained who does not really know what to believe and/or has a different viewpoint/conviction.
Finally if one want to prove MEASUREMENTS on PROFFESIONAL level please show case the following: Bring live musician(s) to play, put them in parallel on a playback system and COMPARE the difference.
As long as we don't have exact output (where also the audience can't distinguish between two) from the playback system we can dance in a loop, masure whatever and however we want but we CAN'T proove anything there.
Total nonsense. Absolutely impossible too as instruments all have their own dispersion pattern, change of timbre depending on how 'loud' they are played and cannot reproduce exactly. Any recording is merely a registration and has to be manipulated and mixed to come to an end result which is to be reproduced on 2 transducers in another room.
And in reverse engineering approch we need try to figure out where the problems are in a playback system, correct them, measure them and do this as long as we need to match the output. CAN we do that? do we KNOW how to DO THAT?
On the electronics side sure... within boundaries. In acoustics it becomes another matter. One can only address some of the issues that occur there.
Once we do that then we can state WE HAVE A PROPER SOUNDING EQUIPMENT AND A PROPER MEASUREMENTS IN PLACE as a REFERENCE POINT FOR ALL THE OTHERS.
For DACs and amplification this is really easy to do up to certain levels.
The difficulties arise in:
The used recording
The used transducers
The used acoustic conditions
The used playback level (SPL)
The used listening position
The experience listeners have and knowledge they poses to describe heard things in a way that is understandable
The perception capabilities.
The rigor of the 'test'/'comparison' if that is the goal.
Until them we all can DERAM ON on stories and feritails about the measurements and sounding gear..
We all can dream on anyway. Regardless who it is and what their dreams/goals are.
This is a reality, everything else is a nice hobby. And yes, I'm in this hobby too so don't feel accused
Sound reproduction other than for 'reviewers' and professionals in the recording/sound reinforcement is a hobby.
Salespersons for AV gear also are professionals but in selling gear to people.
Some think they offer good advice, some do offer good advice but in the end they have to sell in order to make a living and either sell lots of things or make large profits on less items.
Everyone enjoying reproduced music does this for a hobby. Some are more passionate than others and some have more 'real' knowledge than others. There just aren't any extremely knowledgeable judges but many people think they are.
Such is the state of this hobby.... for ALL of them no matter where on the objective-subjective scale they may be.