The Audio-Technica ATH-M40x are decent headphones with outstanding, studio-quality sound. They feel sturdy and are fairly comfortable but offer no control options for your audio. They also only provide passive isolation, which might not be enough to block the noise of some listeners' commutes.
The Audio-Technica ATH-M40x have a bland studio design that's well-built and comfortable. The plastic earcups are dense, and the headband is reinforced with a metal frame. This makes the headphones sturdy and able to handle several drops without getting damaged. Unfortunately, they're not sufficiently stable to be used while doing sports or other high-intensity activities (see our recommendations for the best sports headphones). They also don't have any control options for your audio.
The Audio-Technica M40X have a very understated studio design that might look a little bland for some. They have an all-black color scheme with silver highlights on the back of the oval ear cups. Their design is very similar to the ATH-M50x. They look good but offer nothing remarkable with their design.
The large ear cups of the ATH-M40x fully encompass the ears and do not apply too much pressure to the head. They also swivel, which makes them easy to adjust. They are more comfortable than the Beyerdynamic DT 770 but the padding used for the headband and ear cups is a little rigid and squeak when moving or adjusting the headphones on your head.
The ATH-M40X, like the ATH-M30X, are decently portable headphones. They are on the larger side of over-ear headphones but 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 or very long audio cable is also a bit cumbersome to carry around but unlike the lower-end model of the series are detachable.
The ATH-M40X feel robust and durable. They have a mostly plastic design that's dense and able to handle a fair amount of physical stress. They have a metal frame that reinforces the headband, and the ear cups feel sufficiently sturdy to withstand a few drops without damage. The joints, on the other hand, are susceptible weak points where these headphones could get damaged and may weaken over time.
The Audio-Technica M40x are decently stable on the head. They are not designed for sport, so they will easily slide off your ears while running or jumping. However, for casual listening sessions, they will stay in place even if you put them on, tilted and little further back than usual. The detachable cable is also a plus for stability, as long as you remember to unlock the cable from the ear cups.
The Audio Technica M40x are a good sounding pair of closed-back over-ear headphones (see our recommendations for the best over-ear headphones and the best over-ear headphones under $100). They have a well-balanced and extended bass, an excellent mid-range and a very good treble. However, their bass delivery is prone to inconsistencies, especially if the user is wearing glasses, their distortion performance is about average, and they lack an open and spacious soundstage.
Isolation is passive for the Audio-Technica ATH-M40x. This means that only the seal created by the over ear fit of the ear cup will prevent noise from seeping into your audio. Unfortunately, the seal is not enough to block the low-frequency noise of a plane or train. Fortunately, they do not leak too much but are audible to people around you at very high volumes.
Poor isolation. The passive isolation provided by the ear cups does a decent job of blocking treble sound. However, as the frequency lowers, so does the effectiveness of the passive isolation. Their effect below 400Hz is minimal.
No active features.
The Audio Technica ATH-M50x are very similar to the Audio Technica M40x, but they have a slight edge over them. They feel a bit sturdier and better-built than the M40x, and their audio reproduction is slightly more accurate and neutral. Also, the M40x have elevated distortion, so they might sound a bit impure at high volumes, while the M50x will sound cleaner. Both headphones will give you great sound and are also great options for critical listening, but the M50x offer one of the best values on the market due to their great price-to-performance ratio.