I'm not sure why but the monitor/tracking headphone has always been my interest. There shouldn't be any need to go beyond what the creators, musicians, engineers etc use is the way I think. If even a pro engineer will not use higher end models, then maybe they are not exactly necessary.
So for a person who values hearing details ('hires') and less bass, on a budget, in a shared environment, speakers is out of the question. But as for headphones, audio-technica’s 2014 M30x has had me pondering for some time. At the time I bought it, I was really expecting an affordable good performer labelled ‘studio monitor’. A-T’s M30x would ordinarily give way to M40x, and this is clear from rankings where M30x ranks very low. Hearing M30x, I was very satisfied. I didn’t have to go to a store to test it. I had had enough of ZX110 which I didn’t know enough to EQ at the time. Since we’re not expecting speaker-like quality with headphones, M30x seems to be the right balance of various factors. For me personally, M30x trumps all the rest of the M series, since resolution isn’t a big deal for me. I’m also not really into the wireless world, nor the 1AM2, Z7M2 or Z1R with reputations of being able to ‘make you want to listen forever’.
Some audio buffs are into IEMs, others, headphones and portable audio. Still others use speakers and claim it is the proper pure audio. But nowadays headphones are really gaining ground as the loudspeaker of choice. Headphones come in types including open/closed back, with higher impedances for open backs (better sound almost like speakers and less affected by DAC impedance). They can be on ear or over ear. They can have different transducer types. IEMs can come in earbuds or earplug types. Knowing that headphone distortion is far worse than DAC distortion really changes the way a layperson views measurements of DACs.
I didn’t recognise headphones until 2019 when I bought my first pair. Until then all I had was a Qantas headphone. ZX110 opened my eyes to headphones. But until today I didn’t really think about A-T’s headphone lineup. The M series goes from 20 to 70, and shops like to rank them in order, preferring the resolution of 70x. In fact, many contradictions exist in terms of claims regarding treble and bass. Some will relegate M20-40 to a listening category and only consider 50 onwards to be studio grade. I think I got M30x after reading positive reviews of it, and due to its price, with delivery. I was looking for a 40 mm driver CD900ST replacement or equivalent. Actually there are plenty of CD900ST copies, at a much lower cost. In reality M30x is very different. They advertised it to be focused on mids, while M40x supposedly does all three well. Some considered M30x to have less emphasised mids. It is also for smaller ears since they must fit within the small pads. Some talk about an A-T house sound. Electrical engineers tend to find A-T to have quite a neutral and exact sound. One can also infer from the way M30x has a fixed 3 m cable for musicians e.g. playing a guitar and monitoring its recording, that it is for musicians’ monitoring needs. The designer’s intention was already to place M40x as the first model for engineers to use. RTings states that M30x has differences in the high frequencies compared to M40x.
A-T also had a 2009 SX1a model for Japan only. It didn’t catch on and is mostly unknown, despite its good build quality and cheaper price than 900ST. Also, a good comparison of M30x and M40x can’t be achieved easily given the differences in impedance and drivers. I prefer around 50 ohms. 63 ohms of 900ST is somewhat high. Many talk about how different M1ST is, but actually it’s simply a modern driver with a clearer bass you can focus and pinpoint on, in line with current music tastes. Highs are not so different from 900ST and the hires exaggeration isn’t quite correct.
From random FR graphs I eliminated many headphones and chose M30x. It now appears I badly misinterpreted the FR graphs.
So my EQ settings after much tweaking became +12 dB at 5 kHz Q 0.8 and +5 dB at 250 Hz Q 0.5. It lifts the veil on vocals that some users complained about, although it does make the headphone overly bright compared to stock. Then it adds a bit of overall low end though it isn’t obvious for most sources. For example piano sound remains unchanged. This is based on the FR graphs showing a 20 dB dip at 5 kHz which correlates with very high THD at 5 kHz. There is also a 5 dB dip at 250-80 Hz?
AUTEC's M series is actually very confusing and could be why the simpler CD900ST prevails even after more reviewers dispelled the myths surrounding CD900ST in recent years.