All this talk about house curves and preferences sounds subjective. But when it comes to acoustic music, we can apply a reference guideline. What do most concert halls do to the sound? What is the spectrum (frequency vs. energy) of a voice or musical instrument: (A) close miced, (B) taken from the 1st row of seats, (C) taken from the 10th row?
Remember that the energy of a wave is essentially amplitude * frequency. So a sound of twice the frequency has twice the energy if its amplitude is the same. This also means that if a musical instrument emits equal energy at all frequencies (it doesn't, but it's still a useful example), the amplitude of its harmonics will taper by about 6 dB / octave. Most naturally occurring sounds (whether music or other noises) roughly follows this: whatever their fundamental is, amplitude drops as frequency increases above it.
I don't have the numbers but experience taught me the further away you get from the musicians, the FR tilts more downward. A flat (no downward tilt) in-room response sounds bright and edgy, like sitting next to the musicians on stage. Some recordings are bright, some are dull. Some are close-miced, some not. So I experiment and go with a "house curve" that strikes a balance making a variety of different well-made recordings all sound as natural as possible, meaning as close as possible to the real thing. I find that something like 1 dB / octave from 30 Hz to 20 kHz (a little more or less, depending on the room and your taste) sounds well balanced like good house seats with most recordings.