Sennheiser IE 40 PRO

The manufacturer claims to have taken great care to provide a warm, detailed and natural sound all at once. Combine this with the declaration that these headphones deliver performance levels usually found with in-ears used on stage, and the IE 40 PRO has some serious points to score in this test review.

What’s included?

Inside the packaging of the Sennheiser IE 40 PRO you’ll find the device itself, plus three pairs of silicone ear moulds in various sizes, along with a further pair of memory foam ear moulds. A cleaning tool is also included, as is a carry case. With the case however, comes a shortcoming – after inserting just the earpieces and the cleaning tool, the case is already full. That’s without the headphones themselves being added.

Form, colour and function

Sennheiser in-ears are relatively flat, yet the design here is one dominated by curves. In addition to the black version tested for the purposes of this review, the IE 40 PRO is also available in transparent housing. Sufficiently strong bend protectors are provided at all the important stress points, while the cable is removable for easy transportation and maintenance. It is immediately noticeable that the plugs are a little tight, but they’re nowhere near as tricky to remove from the housing as plugs of the MMCX connector system – definitely a thumbs up, as far as I’m concerned.

The possibility to adjust the in-ears for better bass reproduction is certainly innovative. The length of the earpieces is variable and can be adjusted to the depth of the ear canal with ease. Two grid positions are on hand for this purpose, allowing the ear mould to be snapped into place with ease.

Inside the IE 40 PRO, a newly developed 10 mm broadband convertor is utilised. I was curious to see whether the sound of the in-ears would be any more powerful and precise because of this. The IE 40 PRO has a lightly-vibrating diaphragm, designed to amplify this effect even further.

Technical specs in stats

The dynamic converters reproduce audio in the frequency range from 20 Hz to 18 kHz. On paper, this transmission range is slightly limited in the high frequencies, since the human ear can usually hear up to 20 kHz. The impedance of 19.4 Ohm ensures these are well suited for use with pocket transmitters and low-power headphone amplifiers. This allows musicians and DJs to use the IE 40 PRO in almost any live setup imaginable. The IE 40 PRO drivers, equipped with neodymium magnets, deliver a maximum sound pressure level of 110.4 dB SPL when measured for this test. These headphones can therefore prove to be quite powerful. According to the manufacturer, the IE 40 PRO succeeds in blocking out external noise measuring up to 26 dB.

Sound

First things first, the sub-bass of these in-ears is phenomenal. This is particularly true if the position of the ear moulds is selected so that they can extend a little further into the ear than usual. In the mids, the sound is defined by a rich level of detail. This ensures, among other things, a higher level of speech intelligibility. However, the sound is clearly too sharp at high frequencies. Depending on the monitor setup, ‘s’ and ‘sch’ sounds, as well as cymbal drums, occasionally cause hissing.

However, at the same time, the upper treble range is so well represented that the sound of the headphones appears open, even airy. This was not to be expected due to the limited frequency range, but the fact that the headphones are loud (and I seriously mean loud), proves in practice that they suffer from no distortion, even at higher volumes. The manufacturer hasn’t made any big promises in this department, but the reproduced signal has a very dynamic effect and reproduces transients in detail. The stereo impression is good, not least because of the general openness at work here. For the same reason, the signal resolution is also convincing, with the depth graduation gaining real dimension.

Good for monitoring?

The ergonomic shape of the IE 40 PRO ensures that these monitoring in-ears offer a good fit, right from the off. For use on stage, however, it’s vital that such headphones are comfortable as they will be consistently attached to the wearer. With their bendable wire-enforced cable ends that adapt to the shape of the ear, the IE 40 PRO delivers a genuinely secure fit. This is no coincidence, as the cable is carried over the ear, ensuring the ear itself acts as a strain relief. The in-ear cable is flexible and its 125 cm length allows it to be easily stowed underneath clothing without anything visibly protruding. The soft cable sheathing reduces the rustle that can occur when clothing and cables meet and rub, minimising sound distortions as a result.

Weighing 18 g, these headphones are light enough to be worn comfortably, without pressure building on the ear over long periods. The IE 40 PRO also delivers when it comes to blocking out external noise. This is especially true when the earpieces are adjusted to extend deeper into the ear canal. It’s genuinely amazing what a difference the extra 1-2 mm makes in terms of sound enjoyment.

Expectations

The Sennheiser IE 40 PRO meets almost all professional expectations that I could think of during testing. The fit is comfortable and secure. The handling is easy and again, very comfortable, with a user-friendly plug connection to the ear moulds. The option to adjust the depth of the fit shows that simple solutions can often deliver huge differences and, in terms of sound technology, the IE 40 PRO offers a detailed sound profile that ranges from impressive sub-basses to a detailed mid-range and a surprisingly open high-frequency range.

Sennheiser says that the sound of the headphones should be precise when listening at both low and higher volumes. While this is indeed accurate, I don’t agree with the presumption of balanced sound. For several hours of fatigue-free listening, I would like to see the frequency components above 8-9 kHz in my monitor mix for the IE 40 PRO reduced by a few dB with a filter. However, with this, dampening effects are occasionally noticeable.