This may be a rather bold statement.
After more than 50 years of global experimental listening evidence there must be some areas of audio or electronic engineering which must be redefined.
For example:
Steering away from the subjective objective measurement doctrine towards objective subjective measurements. For example instead of subjectively believing that any harmonic distortion will sound the same and then going on to objectively measuring total distortion, objective finding out by subjective listening tests which order of distortion sounds best and not trying to eliminate it. Of course almost all global community has done that already and it is now widely accepted that single ended amplifiers in class A (electrons flowing all the time) can sound much more realistic and one reason being not eliminating second harmonic distortion in favor of eliminating 3rd harmonic distortion etc and at the same time using its growth for simulating or bringing back dynamic realism. [Hamm]
Other example may be questioning the doctrine of terminating at about 2-3 times load impedance than the anode impedance on triode electron tube amplifiers. May it be that the sound is better when impedance is matched? But whether or not will have to be found by objective subjective listening tests. Other example is whether matched electron tubes in push pull stages sound better by listening tests. Most likely they will not. Matching will eliminate the best part of the 2nd harmonic (octave) creation. It has to be found by objective subjective listening experiments.
Other example may be the doctrine that an octave is a doubling of frequency. This has to do much less with how the human brain perceives pitch (the subjective perception of height of tone measured in mels). x2f is an engineering octave which sounds flat to the human brain whose perception of pitch also depends on intensity [ ], [Stevens]
Other example is the doctrine that frequency response must be flat from microphone to loudspeaker. This may or not be be true at half the side ie at the reproduction end. But certainly not on production end from mic due to many objective subjective effects such as Fletcher Munson curves, Voice effort curves etc [Lowe, Morgan]. A more correct objective subjective goal can be flat frequency response from producer's brain to listener's brain. Since this may sound too exotic at the moment perhaps enough is flat frequency response from singers-actors vocal chords to listener's brain [Lowe, Morgan]. But we are more than 50 years from the discovery of this knowledge, flat frequency response from producer's brain to listener's brain must have been happening on great influential record producer's works of art and engineering. For example ABBA have used Varispeed on vocals [Tretow]. Producers were inside the studio so quite clearly they must have had that sound in mind.
Other example is the doctrine that the ideal amplifier is the one with 0 output impedance ie constant voltage driving of a loudspeaker. This is getting to a point of being rather far from truth [Nelson Pass]
And of course the doctrine that digital sounds better must be questioned too.
Other doctrine to be questioned is that the loudspeaker walls must be thick and energy trapping. [Pleiades linoleum speakers]
Other doctrine that the heater voltage should not be less than specified. [Neumann U47, Pleiades V6]
Other doctrine that electron tubes should not be operated at less than say 6V anode potential with bias approaching somewhat 0V from the negative side. [Pleiades V6, Pleiades bias, Armstrong]
Other doctrine that audio trasformers introduce distortion. This has to be confirmed by objective listening tests and not subjective objective measuring tests. but perhaps this has already been done after more than 50 years of top quality recordings made with so many transformers in the signal path from composer's brain to listener's brain.
Food industry engineering may be based on how the brain perceives taste, why should it be different on audio engineering?
A situation may be similar to music engineering or composing. Elementary doctrines suggest avoidance of musical intervals of 7hs , 9ths etc above bass, yet the subjective objective masters on composing such as J.S. Bach knew how such intervals can be prepared for euphonic brain perception and this had become the basis of high quality popular music of our modern times. [Bach, Niedt].
References:
Tubes vs Transistors (vs op amps), Is there an Audible Difference? - Russel O. Hamm - JAES
Octave Stretch - Terhardt
http://www.mmk.ei.tum.de/fileadmin/w00bqn/www/Personen/Terhardt/ter/top/octstretch.html
Sound and Hearing - Stevens, Warshofsky - Time Life science series
Sound Picture Recording and Reproducing Characteristics - D. P. Lowe, K. F. Morgan - Journal of the Society of Motiion Picture Engineers
ABBA sound - Michael Tretow interview
Current Source amplifiers and sensitive full range drivers - Nelson Pass
http://www.firstwatt.com/pdf/art_cs_amps.pdf
Neumann U47 schematic
Pleiades V6 schematic
Pleiades Bias - euroelectron
Operating Features of the Audion - E. H. Armstrong
https://normanschmidt.net/scores/bachjs-general_bass_rules.pdf
