semi-open headphones

An interview with product management: Semi-open headphones

We spoke to Product Manager Robert Schwarz about Teufel’s new Real Z semi-open headphones. Schwarz explained the benefits of semi-open headphones and why Teufel product management decided to offer this new product.

In audio circles, it’s often said that so-called “open” over-ear headphones offer the best sound quality. What are open headphones and do they really sound better than closed headphones?

First of all, no. It’s really a matter of personal taste, but there are differences. Maybe it’s best if I first explain how closed headphones are constructed and how design effects sound. That will give us a basis for comparison with  other types, namely open and semi-open headphones.

With closed over-hear headphones, the area behind the drivers in the ear cups is completely sealed off from the outside. That means there is no mesh, vent or other opening that allows air to circulate. This prevents your music from leaking out and outside noise from being heard by the wearer. It also creates a sealed chamber within the ear cup which leads to the following effect: Whenever the driver moves, it creates areas of overpressure and low pressure. When the driver moves towards the ear, the low pressure in the chamber will tend to pull it back and when the driver moves away from the ear, the overpressure will push it slightly forward. In short, the movement of the driver will be slightly effected by the air pressure within this sealed chamber.

semi-open headphones from Teufel

What does this mean for sound quality?

Depending on the way the headphones are constructed, it can be difficult for the driver’s membrane to move exactly as dictated by the impulse from the audio signal. Instead, it’s slightly altered by the pressure exerted on it inside the ear cups. The effect is small, but still audible. With certain closed headphones that don’t work to compensate for this effect, the sound can be slightly damped and have less of a 3-dimensional effect. The playback simply won’t be as transparent. Of course, there are closed headphones like our Teufel Massive, MUTE and TURN that do a very good job compensating for the effects of pressure in the ear cups. Still many people prefer the sound of an open headphone.

And how are open headphones different?

With open headphones, the area behind the drivers is well, open. In the case of our Aureol Real, a mesh grille allows air to freely circulate. Since the ear cups do not form sealed chambers, pressure doesn’t build up. This allows the magnet and voice coil to work more effectively. The membrane will start and stop exactly when the signal indicates it should.

This certainly explains the Aureol Real’s transparent sound.

Yes, as an open headphone, it offers very sophisticated playback.

Real Z semi open headphones from Teufel

So this headphone is ideal for classical music and jazz?

Yes, and rock, certain types of electronic, anything with vocals – so also podcasts and things like that.

But what about the bass range? The low end isn’t as strong in open headphones. Why is that?

That’s because open headphones don’t have this “sealed chamber” effect. The closed-off ear cups in closed headphones can hinder the free movement of the headphone’s membrane – this is true – but there’s also a positive effect, namely in the bass range. Especially the use of protein leather in the ear cups prevents air from escaping, unlike a more permeable material like velour. In the case of the Real Z, the protein leather ear cups function like a closed baffle on a loudspeaker: They enhance the bass.

How’s that?

Well, bass frequencies have very long sound waves. They’re so long, in fact, that they can easily travel around the driver or open baffle of a speaker and meet the sound waves that are produced as the driver swings back. This is known as the acoustic short circuit. The same frequency is emitted at the back of the driver but is out-of-phase to the sound waves produced by the front. So the trough of the sound waves from the front meet the peaks of the sound waves from the back. When two out-of-phase sound waves meet, the result is silence. This is what can keep open headphones from producing the sort of mega bass some listeners crave. However, if the low frequency waves can reach the ear without encountering sound waves from the back of the driver, they won’t be canceled out. The protein leather ear cups on the Real Z have this effect.

So the Real Z is transparent but still able to produce powerful bass sound.

That’s right. We wanted to endow the Real Z the best of both acoustic properties: Transparency and powerful bass. Whereas the Aureol Real has a 20 Hz low end, the Real Z can go all the way down to 18 Hz. In addition, the protein leather ear cups on the Real Z function as resonating chambers for a fuller, warmer effect.

This makes it sound like the Real Z is a closed headphone, yet in the description they’re described as semi-open headphones. Can you describe what about the Real Z’s construction is semi-open?

The Real Z is based on the Aureol Real’s open design. That means an open mesh grille behind the drivers allows air to circulate in and out of the ear cups. In order to prevent the sound from leaking out of the ear cups, however, we used a special acoustic filter between the drivers and the metal mesh. This means considerably less sound escapes and less outside noise reaches the ear. Still, compared to a closed headphone like our TURN, the Real Z allows more sound to seep in. Again, this can be an advantage in some situations.

What was the idea behind developing the Real Z? What sort of people would want a pair of semi-open headphones?

Because the Real Z allows the user to still hear some outside noises, it’s ideal for activities like jogging or snowboarding where you would want to pick up certain acoustic signals in your environment. The headphone’s protein leather also make it ideal for these activities since any sweat can be easily wiped off. We’ve also given the Real Z a more robust design than the Aureol Real by employing more real aluminium hardware and improving the overall ergonomics of the device. Don’t get me wrong, the Aureol Real is an incredibly solid pair of headphones, it’s just that the Real Z has even better build quality. Gamers will also appreciate the design because the Real Z is still very lightweight and comfortable.  They’ll also enjoy a highly realistic sound that doesn’t lend itself to ear fatigue – important for longer gaming sessions – and will still be able to hear the doorbell or phone ring.

What about office use? Can the person sitting next to me hear what I’m listening to?

A lot of people in product management at Teufel use the Real Z at their desks and I’ve never noticed any intrusive noise. As opposed to a pair of truly open pair of headphones, the Real Z is definitely the better option for an office environment.

Interesting. What else does Teufel product management have planned?

A lot of exciting things are in the pipeline for portable and other product categories, but I’m sworn to secrecy.

I guess we’ll just have to wait then. Thank you for your time!

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