To the degree that I can parse what you are asking, I think what you want is a “tuning fork”, a neutral audio playback system that serves as the reference sound and what you can compare other systems against. There are numerous choices that are probably good enough, just by going down e.g. Crinacle’s list of headphones.

Something like Truthear Hexa costs about 50 bucks, and should have pleasing tonality for most listeners without requiring use of hearing-damaging levels to compensate for loudness (that’s what the rising bass is all about). Pair it with something basic like the 10 buck USB-C 3.5mm apple headset adapter that supplies known-good amplification for these low impedance headsets, and you should have this “tuning fork”.