The Audio-Technica ATH-M30x are above-average-sounding headphones with a decently sturdy and comfortable design. They don't leak much and won't distract the people around you. However, they are not stable enough for gym use and won't fare as well in loud environments because they don't block much noise.
The ATH-M30x share the same understated and slightly bland design as the ATH-M20x. They're robust enough to withstand a few drops, and they're moderately comfortable. They are also stable during casual listening sessions. However, they will slip off your ears if used at the gym and their featureless design lacks audio controls and a detachable audio cable, which is slightly disappointing.
The ATH-M30x do not change much from the ATH-M20x. They have the same design with minor changes to the back of the ear cups. They also come in an all-black color scheme and have the same understated look as the rest of the ATH-M series. However, the M30x and M20x look more cheaply made than the higher-end ATH-M40x and ATH-M50x.
The comfort level of the ATH-M30x has been slightly improved from the ATH-M20x model. They have slightly larger ear cups that better encompass most listeners ears. They are also not too heavy and don't apply too much pressure to your head. However, like the M20x they can be a little rigid and don't swivel as well as the higher-end models of the same series.
The ATH-M30x are decently portable headphones. They are on the larger side of over-ear headphones but unlike the ATH-M20x, they fold into a more compact format that will fit in a backpack or handbag but will be too large for most jacket pockets. The thick, non-detachable audio cable is also a bit cumbersome to carry around. They also do not come with case or pouch which is slightly disappointing.
The build quality of these headphones is average at best. They can withstand a couple of drops without getting damaged, and the plastic used for their design feels dense and relatively durable. However, the metal frame used to reinforce the headband is thinner than the one utilized for the ATH-M40x or ATH-M50x. They also have exposed audio cables, which connect to the ear cups that can easily get damaged by wear and tear.
These headphones are moderately stable and stay in place during casual listening sessions. However, they're not made for sports and don't exert much pressure on your head which makes them slip off your ears if used at the gym. They also do not have a detachable cable like the ATH-M40x and ATH-M50x and could get yanked off your head if something hooks the cable.
They have an excellent and extended Bass, a very good Mid Range and good Imaging. However, their Treble lacks a bit of presence, and they have a mediocre distortion and Soundstage performance.
These headphones only provide passive isolation. They can block some high-frequency noise with the quality of the seal the ear cups create around the ears. Unfortunately, it's not sufficient for loud environments. They will not fair well on a plane or a train unless you are listening to your audio at really high volumes. On the upside, they don't leak too much but will be audible to the people around you in a quiet office.
Poor isolation. The passive isolation provided by the earcups performs well in the treble range. They consistently provide more than 20dB of isolation. However, the overall amount of isolation in is only about 10dB the mid-range and 0dB in the bass range.
Average leakage. The significant portion of the leakage is between 500Hz and 3KHz, which is rather broad. However, the overall level of the leakage is quite low, which makes up for the broad leakage profile.
No compatible app.
Mediocre overall design. They would perform adequately well as everyday headphones, but lack a decent control scheme, and the passive isolation is a little weak.
The M30X have a surprising amount of audio fidelity for their price range but have a poor soundstage because of their closed back design. They perform above-average for neutral listening but may lack a little openness.
Not ideal for commuting. The weak noise isolation is not sufficient for loud environments.
Not designed for sports. They're a bit too bulky and unstable for high-intensity exercises.
Average at best for office use. The passive noise isolation too weak to block the chatter of a busy office. Mediocre comfort and no audio controls.