In-Ear Headphones - Technical Background

First, I need to make it clear that in-ear headphones are also referred to as canalphones or In-Ear-Monitor (IEM). To assure a better sound experience, the headphone creates a sealed acoustic chamber. The eartips’ shape, size and material used create the sound isolation. Using some small diameter cables increases the stylishness of the headphones. Contrary to popular belief, although this may appear easy to make and fit, they can turn out to be much more difficult than classic headphones.

As for the sound-creating mechanism, the transducers provide some filters to improve this. You can see the basic components of a set of in-ear headphones in the image below.

(Image courtesy of ImageInEarMatters.net)

There are two types of transducers: Dynamic and Balanced Armature (BA). The Dynamic transducers are cheaper to produce; you can find them in the cheaper entry level and lower class. Their diameter varies from 8mm to 16 mm. The moving coil (dynamic) transducer's working principle is based on its big speaker counterpart technology, built into a smaller size. A stationary magnetic element affixed to the frame of the headphone creates a magnetic field.

A diaphragm found inside this is actuated by the attached voice coil to the diaphragm, when some audio signal passes through the coil. The alternating current creates its own magnetic field. The two fields react and, as a result, the diaphragm moves. This implies moving some air, which creates the sound. With this technology, you can better create the lower frequencies. Therefore, most of these headphones tend to offer an oversaturated bass.

The Balanced armatures are smaller in size and more expensive to construct. However, due to their size you can find even 2-3 of these in each earphone. This allows them to provide a wider range of sound frequency, giving a better sound experience. This method tries to eliminate the stress on the diaphragm. It consists of a moving magnetic armature that is pivoted so it can move in the field of a permanent magnet.

Once centered, there is no force on the armature (this is why they are described as "balanced"). When electric current passes through the coil, the armature rotates one way or another, and with it moves the diaphragm to create sound. While it needs some force to restore the balance of the system after a movement, the method remains one of the best ones as far as energy efficiency. Its limits are normally between the 20 Hz and 16 KHz range, just inside what humans can hear.

(Image courtesy of Wikipedia.com)

Now that we've seen how they work, let's see what arrives on the markets. For this, I will write a small review of the Sennheiser while also presenting the general traits of a quality headphone.

Next: Sennheiser CX300 >>
 

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