Sennheiser HD 400 Pro

With the HD 400 Pro, Sennheiser presents open headphones for recording studios as well as mix and mastering engineers. Their sound is supposed to be precise and natural at the same time. As a professional workhorse, they are compatible with the software plug-in dearVR MIX from Sennheiser subsidiary Dear Reality, which recreates different listening environments. In this way, mixes created with the headphones should sound equally good in as many different listening environments as possible. Which brings us to the question: How does the Sennheiser HD 400 Pro actually sound?

Sennheiser HD 400 Pro Package

But first, let’s take a look at the package. In addition to the headphones themselves, the box contains a 3m coiled cable and a straight cable of just 1.5m in length, both with 3.5mm jack plugs. In order to be able to use the headphones flexibly, a 6.3 mm screw adapter is also included. All contact surfaces are gold-plated for corrosion protection. The package is straightforward but enables flexible use of the headphones.

Material and construction

The exterior of these headphones is made entirely of matt black plastic. The size-adjustable headband is no exception. This makes the Sennheiser HD 400 Pro significantly lighter than other headphones in this price range, which seek to indicate by their weight alone that they want to be taken seriously as reference tools. Replaceable velour ear pads should ensure long-lasting wearing comfort. The sparse design of the headband padding is already familiar from other models in the HD series. Overall, these headphones have a modern and appealing look and, despite their plastic appearance, make a solid impression throughout.

Technology and values of the Sennheiser HD 400 Pro

The HD 400 Pro’s ear cups feature sound transducers developed by Sennheiser, which have not been installed parallel to the head but at a slight angle. This is supposed to lead to an improved stereo image and makes us eager to try a listening test. The HD 400 Pro also has more to offer in the frequency range than many competing models. In the bass, its reproduction reaches down to an ultra-low 6 Hz. And in the treble, too, the performance is exceptional. It reaches up to 31 kHz. This means that the headphones reproduce audio in a spectrum that is significantly larger than the typical human hearing range. The highest possible sound pressure level that they can output without distortion is 110dBSPL. Therefore, mixdowns and masterings can be checked even at very high volumes. In order to achieve these volumes, however, the voltage output from the headphone amplifier or output should be significantly higher than that of smartphones, laptops, etc. Otherwise, the 120-ohm impedance of the HD 400 Pro prevents them from being used to listen to audio at a correspondingly loud level.

Handling

In order to be successfully used as a day to day work tool, a pair of headphones not only has to put on a solid performance but also be consistently comfortable. The Sennheiser HD 400 Pro offer this with their interchangeable cables that plug into the left earcup. This means that the cable does not interfere with mixing or other activities by hanging in front of the body. In addition, these headphones are nice and light, weighing only 240g without the cable. This is important when using headphones for several hours. To allow you to adjust the headphones to the shape of the head, the headband of the HD 400 Pro has a slightly gridded size adjustment. Conveniently, it remembers the last size set. Its ear cups can only be rotated and swivelled slightly. But this is perfectly sufficient for easy adjustment of the headphones to different head shapes. Even though the contact pressure is not particularly strong, the headphones still fit very securely.

The cable attachment is done by a plug-and-swivel mechanism and ensures both a quick change and security when pulling the cable. At 1.5m long, the straight cable is well suited to working at a media or mix station without excess cable length. Those who need more freedom of movement will find it in the 3m spiral cable which is also included. The earpads can also be changed. To do this, their support plates are clipped firmly to the ear cups of the headphones. This, too, is quick to do and ensures an ultra-secure fit for the pads.

Sennheiser HD 400 Pro sound

Doing a sound check with these headphones is exciting because Sennheiser advertises the HD 400 Pro as having an uncluttered, almost flat frequency response and an analytical and neutral sound. These are high claims. The isolation from external noise is indeed very low and therefore absolutely successful for these open headphones. Conversely, the isolation from the outside is of course not as good. For this reason, the HD 400 Pro are not suitable as monitoring headphones for recording purposes with miked sound sources. But there are several closed models available in the HD series for this purpose in different price ranges.

It becomes clear right from the first notes that the Sennheiser HD 400 Pro are detailed in the highs, but not annoyingly brilliant. The tonal harshness sometimes heard with other headphones is absent here. As is typical for open headphones, the Sennheiser have no annoying compression in the bass range. Nevertheless, they are by no means thin in the lower frequencies. Even the deepest sub-basses are easily perceptible. This is where the ultra-wide frequency range of their reproduction comes into its own.

Mids are differentiated and are by no means as prominent as with other headphones. If you listen to vocals in high-class pop productions with the HD 400 Pro, they seem homogeneously embedded in the sound. The same applies to guitar music. If you mix rock and metal songs, you can listen through the wall of sound of distorted guitars with these headphones without losing focus on other frequency ranges. The super high-frequency range that the HD 400 Pro emits also adds sufficient sparkle to the overall sound, but without drawing attention to itself. In the area of dynamics, these headphones impress with good impulse behaviour. Drum sounds are reproduced concisely, sudden tuttis of classical music are punchy. The stereo image is good but didn’t quite blow me away as I promised by Sennheiser’s advertising. The unusual alignment of the diaphragm simply had no perceptible effect on my listening experience. Sennheiser talks about the sound of the HD 400 Pro being “natural”. And indeed, it offers a strong tonal balance and reproduces audio in an unagitated manner. Its sound characteristics seem dynamically soft and frequency-warm. And it is precisely this sound signature that the test device’s profile in the dearVR MIX software plug-in, which is optionally available from Sennheiser’s subsidiary Dear Reality, is designed for. If you want to realise different virtual listening environments with the HD 400 Pro, then you will find what you are looking for in this plug-in.