I never used an equalizer because i never needed one...
I bought my Hidizs dac to serve the K340 and i needed his internal equalizer like the tone control for the K340...I did not want to buy a sophisticated EXTERNAL equalizer, because the task was simple and easy to do around 1000 hertz...
I dont used any equalizer with my other headphone and i never need the equalization nor the tone controls really for them...All those years my tone controls were almost unused save by curiosity trials...
In my room i did not need an electronical equalization either and anyway i did not want to invest big money in a good one ....
I needed a mechanical equalization which i created with a grid of mechanically tuned 100 Helmholtz resonators distributed in some location in bundles to improve the relation between my ears listening position each speaker of the Mission Cyrus 781 in relation with each ears and the room pressure zones distribution...
The K340 is one of the most complex headphone ever designed, with his two cells and his inner dual chambers with the 5 Helmholtz tuned resonators and a transformer for the crossover point ...
It reacted to the source and too any change negatively or positively very strongly, any modification , mechanical , electrical or acoustical impact the soundfield impression...
Single membrane headphone with no internal resonators, as most headphones are, are more previsible in their output... The K340 has aged and need care to reach his optimum... It is not a simple headphone, it is a pair of speakers for the ears, it is why i needed tone controls too +equalisation to optimize them for my own ears... Even the choice of pads thickness and density is critical, i tried five pairs... 😊
I never remember you saying anything about using EQ in the past with your previous system but then, I’d never noticed the tone controls on the Sansui before. My poor observation skills! ;o)