Without Realphones correction:
Out of the box, the headphones sound comfortable, there are no sharp rises in the all frequency range. The range up to 800 Hz is perceived quite linearly, and the upper middle and top are slightly weakened. The middle in the range of 500-1500 Hz feels slightly elevated. The tonal balance is somewhat similar to the Sennheiser HD 650, but in the MM-500 the edges of the ranges are straightened out more, that is, more sub-bottom and top.
The detail across the entire spectrum is higher than that of the Audeze LCD-X/XC, but the clarity of the sound, in my opinion, is slightly inferior. Attacks and releases of medium and medium-low frequencies are worked out quickly, thanks to which the headphones feel very articulated and the reverberation tails are heard better than in other headphones. The low frequencies are quite punchy and also well articulated. But the medium-high and high frequencies against the background of the low-frequency range seem more smoothed than we would like.
The combination of the decline of high frequencies in the frequency response and the “de-esser” effect gives a feeling of a small “cloudiness”, but at the same time the integrity of the sound. Virtual sound sources feel like they are alive. There is something similar, for example, in Audeze LCD-X/XC and Sennheiser HD 800 S. Spatial qualities are also similar to Audeze LCD-X - it seems as if virtual sound sources are “outside the head”, but the effect is not as pronounced as in the Sennheiser HD 800 S.
With Realphones correction:
Thanks to the good detail, the headphones demonstrate nonlinear distortion in music very well. The reverberation fades are also clearly audible.
After correction, the tonal balance becomes correct, but due to the unusual behavior of high frequencies, the effect of “ultra-high contrast” of the mid-HF range appears. This property is typical for mastering-level monitor systems.
Speaking about the nature of headphones, we can say that commercial pop music in them sounds catchy, a little harsh, perhaps a little “pretentious". At high volume levels, there is a “veil” effect.
However, in academic music (and in general any audiophile-level music), the sound is impressive! Low-level details, sounds and performance noises are clearly captured. However, not as clearly as in Audeze LCD-X/XC.
The coloration of the MM-500 is quite strong and it is most pronounced at high frequencies. There is an effect of “friability” on sibilants and high-frequency transients. They are detailed and bring some kind of amazing “sparkle”.
Despite some color, the headphones demonstrate the technical quality of the music being played without compromise! If the track is mixed well, it's easy to hear in Audeze MM-500. If the track is sharp, or muddy, or reduced to a lack of dynamics, the headphones will show it exactly.
Audeze MM500x makes it easy to feel the real sound quality of the recording.
The timbres of the instruments sound freely, openly. Attacks in the entire frequency range are good, transients do not “shoot” and at the same time do not “chew”. Releases are felt at the highest level - all sounds fade out exactly as the sound engineers and composers intended. I was especially pleased with the confident punch at low frequencies, the pulse of the barrel is clearly audible.
Overall impression (with correction and emulation):
Headphones are quite capricious and very sensitive to musical material and to the position on the ears. It is also worth noting that the headphones have a specific and unstable directional pattern: high frequencies are directed by a narrow beam, which is why at the slightest shift from the axis, their number significantly changes. But if you close your eyes to these nuances, we can say that this model is very worthy!
These headphones are not suitable for everyone, but if you like their unusual sound character, then you will be satisfied with the purchase.
MM-500 is quite accurate in terms of timbres and dynamics, and can be perfectly used in mixing.
But their sensitivity to the nature and quality of the musical material makes them especially interesting for mastering as well!