The Sennheiser IE 40 PRO are well-designed in-ear headphones that have an acceptable sound signature. They don’t have the same comfortable fit as some other similarly designed headphones, but they still block a good amount of ambient noise, especially work environment noise. They're also well-built, though their detachable cable is fairly loose and comes off easily. The IE 40 PRO are decent wired headphones but won’t be the best option if you can’t find a good fit.
The Sennheiser IE 40 PRO are well-designed in-ear monitor headphones. They are pretty straightforward as they don’t offer in-line controls and have a typical in-ear fit. They are well-built and their cable is detachable, although it feels a bit too easy to disconnect from the buds. They are very similarly designed to the Shure SE215, but fit fairly differently in the ears and might feel uncomfortable for some.
The IE 40 PRO have a similar design to the Shure SE215, but they sit differently inside the ear. They enter your ear canal fairly deeply and they feel more like typical in-ears. If you dislike the fit of these kinds of headphones, you'll likely experience similar discomfort with the IE 40 PRO. On the upside, they come with 3 tip sizes and one foam tip option as well, which some people may find more comfortable. If you can achieve a good fit, they are very lightweight and you can barely feel the headphones sitting inside your ears.
Like most in-ears, these headphones don’t trap heat inside your ears and they stay fairly cool during long listening sessions. This makes them a decent option for sports as they won’t make you sweat more than usual. You shouldn’t notice a big difference in temperature when wearing them.
The Sennheiser IE 40 PRO are well-built in-ears, but aren’t quite on par with the Shure SE215. The buds are dense, but the material used doesn’t feel as durable. Also, even if their cable is detachable, it is fairly easy to accidentally disconnect it from the earbuds when not around your ears. This gives it a cheap feeling since the connection doesn’t feel secure and you might easily lose the earbuds. They still feel durable and sturdy, but they aren't the best-built option.
The ear-hook design of the IE 40 PRO helps with their stability. They shouldn’t fall to the ground when using them for running. However, head movement might make the buds move inside your ear a bit. They should be fine for the occasional jog, but this wasn’t their intended use. Although the cable could easily disconnect from the earbuds, they are more secure (and won't detach as easily) when wrapped around your ears.
The Sennheiser IE 40 PRO are passable-sounding in-ear headphones. They have good bass, a well-balanced and even mid-range, and a fairly flat treble. However, they might feel light on thump and rumble and their bass is slightly boomy. Also, sibilants (S and T sounds) may feel overly sharp and piercing on certain bright tracks. Overall, they won’t be the ideal choice for bass-heavy music with lots of sub-bass like dubstep and EDM, but can be a good option for vocal-centric music.
The bass performance of these headphones is good. LFE (low-frequency extension) is at 45Hz, which is decent. This and the 5dB dip in low-bass indicates that they might be lacking in sub-bass and thump and rumble common to bass-heavy genres like dubstep and EDM. There’s a tilt favoring higher bass frequencies, making the overall bass light on thump but slightly boomy.
The mid-range of the IE 40 PRO is very good. The 3dB bump in low-mid is actually the continuation of the high-bass overemphasis. This tends to thicken the vocals and lead instruments and make the overall mix sound slightly cluttered. However, mid-mid and high-mid are much better balanced, meaning the upper harmonics of vocals/leads will be reproduced properly.
The IE 40 PRO have a decent treble range. The response throughout the range is fairly flat and even until 10kHz. There’s a small dip in low-treble that will negatively affect the detail and brightness of vocals and leads. The high peak starting at 9kHz will also make sibilants (S and T sounds) overly sharp and piercing, especially on already bright tracks. However, not everyone will hear this as intensely.
The frequency response consistency is excellent. If the user is able to achieve a proper fit and an air-tight seal using the assortment of tips that come with the headphones, then they should be able to get consistent bass and treble delivery every time they use the headphones.
The stereo imaging performance is great. The weighted group delay is at 0.17, which is very low. The GD graph also shows that the entire group delay response is below the audibility threshold. This ensures a tight bass and a transparent treble reproduction. Additionally, the L/R drivers of our test unit were very well-matched, which is important for the accurate placement and localization of objects (instruments, voice, footsteps) in the stereo image. However, these results are only valid for our unit and yours might perform differently.
The soundstage is poor. This is because creating an out-of-head and speaker-like soundstage is largely dependent on activating the resonances of the pinna (outer ear). The design of in-ears and earbuds fully bypasses the pinna and doesn't interact with it. Also, because these headphones have a closed-back enclosure, their soundstage won't be perceived to be as open as that of open-back earbuds like the Apple AirPods 2 2019, Google Pixel Buds, or the Bose SoundSport Free.
The Sennheiser IE 40 PRO have an in-ear fit that blocks a decent amount of noise passively. They create a fairly decent seal that prevents noise from seeping into your audio, but they won't be the ideal option for commuting and when in loud environments. They don’t isolate well enough for most commutes via public transit since they don’t block engine rumbles that well. On the upside, they are good at blocking work environment noises. You should be able to block even more noise if you're playing your music at high volumes. Also, since they barely leak, you won’t distract those around you.
The isolation performance of the IE 40 PRO is decent. In the bass range, where the rumble of airplane and bus engines sits, they isolate by about 2dB, which is negligible. In the mid-range, important for blocking out speech, they reduce outside noise by 18dB, which is good. In the treble range, occupied by sharp sounds like S and Ts, and fan noises like A/C systems, they achieve more than 32dB of isolation, which is also good.
The leakage performance is excellent. Like most other closed-back in-ears, these headphones don't leak in the bass and mid-ranges. The significant portion of their leakage is in treble in a very narrow range. The overall level of the leakage is very quiet too. With the music at 100dB SPL, the leakage at 1 foot away averages at 26dB SPL and peaks at around 44dB SPL, which is lower than the noise floor of most offices.
These headphones don't have a microphone.
The IE 40 PRO are wired passive headphones that don't have a battery and don’t support an app.
The Sennheiser IE 40 PRO are straightforward wired in-ears. They offer no delay when used for watching videos or playing games, but you’ll be limited by their cable’s range. They can’t be used wirelessly unless you get a Bluetooth adapter and replace their detachable cable.
The Sennheiser IE 40 PRO are decent in-ear headphones with decent sound quality, but they won’t necessarily be a better option than other similar in-ear monitor headphones. They offer good value overall, but they aren’t as comfortable as other options on top of not having a great noise isolation performance. See our recommendations for the best wired headphones, the best earbuds and in-ears, and the best cheap earbuds.
The Shure SE215 and Sennheiser IE 40 PRO are pretty similar in-ear headphones, but each are slightly better in different categories. The Shure are better-built as their detachable cable isn’t as loose as the IE 40 PRO’s, and the buds feel a bit better-made. Also, they fit better inside the ears, making them more comfortable and creating a better seal for excellent isolation. On the other hand, the IE 40 PRO have a better treble range reproduction as the SE215 have a broad dip that affects the detail and brightness of those frequencies. However, the IE 40 PRO have a significant lack of low-bass.
The Sennheiser IE 40 PRO are slightly better critical listening in-ears than the Sennheiser Momentum In-Ear. They are better-built than the Momentum and have slightly better audio reproduction. On the other hand, the Momentum might be more versatile for casual listening thanks to the in-line remote, and their fit blocks more ambient noise, which will be better for commuting and traveling. They also have an in-line microphone for calls that the IE 40 PRO doesn’t have.
The 1More Triple Driver are better critical listening headphones than the Sennheiser IE 40 PRO. They are slightly more comfortable thanks to their angled design, but they don’t have the detachable cable of the IE 40 PRO. Sound-wise, they are noticeably more neutral, especially since they don’t have a bass roll-off in low-bass. Their fit isolates about the same amount of noise as the IE 40 PRO too. They have a microphone and in-line controls, which is more versatile for everyday casual use.
If you like bass-heavy music, the TIN Audio T3 will be a better choice than the Sennheiser IE 40 PRO. Their sound profiles are fairly similar, but the low-bass of the T3 is more accurate and doesn’t lack thump like the IE 40 PROs. The TIN Audio T3 are also better-built and feel more durable. Their bud design creates a better air-tight seal and will isolate against ambient noise very well.