DPA 4560 CORE Binaural - in-ear microphone

Are you sure there is no mistake in the title of the article? Microphone in your ear? Not many people in the world seem to sing with their ears, so I'm guessing it's the headphones or the headphone mic?

Oh no. There is no mistake, and these microphones, like headphones, are installed in the ear canal of the recording person. No wonder the name of the product contains the word "binaural", which means a special stereo recording technique in which the microphones must capture exactly the sound that you hear. We are talking about the preservation of all phase relationships and the influence of the so-called acoustic shadow, thanks to which we perfectly orient ourselves in space and recognize the directions from which sounds come.

Mobile recording

To take full advantage of the possibilities offered by the DPA 4560 CORE binaural system, it is definitely worth purchasing the compact DPA MMA-A audio interface, for which there are practically no analogues on the market in terms of quality, dimensions and, above all, the ability to directly connect MicroDot format terminals.

Another thing is to download a free application for iOS, the task of which is to control the interface on our iPhone or iPad. There is also the installation of some kind of audio recording tool (the DPA application does not). The choice is wide here, but I suggest using the free Hokusai 2 app, which allows you to record 24-bit WAV format, offers simple editing at a basic level, and allows, among other things, for integration with Dropbox so that you can send recordings to desktops without any additional combinations.

binaural

In this configuration, the microphone carrier is a live stand rather than a sound source. The stereo signal recorded in this way has all the spatial values ​​that make it possible to obtain a reliable-sounding sound material. Now that we know how it works, we can easily imagine the range of applications for this type of microphone. You're making a kind of movie and you want to get the exact sound effect that reaches the ears of a soldier running down the beach while planes are flying around, grenades are exploding and rifles are being fired. And all this in a helmet and with all combat equipment. Even if such a recording is not ideal in terms of quality, it will at least create a basic, believable-sounding layer on which you can layer effect sounds in sync. It also greatly simplifies the recording process on set.

Another example, also from the world of cinema, is a cameraman with a binaural microphone recording spatial audio from the camera's point of view - an invaluable thing in the context of creating post-synchronization and maintaining sound fidelity. And this is just the beginning, because in this way you can record almost anything and almost anywhere, especially where the view of the microphone is not very visible. Dialogues? Podcasts? Surrounding? Over-ear headphone tests? Psychoacoustic experiments? The idea of ​​binaural notation is so beautiful that it is impossible to resist. And with the DPA system, we can be sure that we are working in the area of ​​the highest possible quality.

design

The 4560 Binaural are not the first or only in-ear headphones on the market. In addition, they are not a completely new product, but a combination of existing ones, based on a pair of excellent miniature 4060 CORE omnidirectional capsules and a headband from the 4266 Flex kit. The capsules have been selected to maintain a performance that does not exceed ±1,5 dB. The kit includes two sizes of foam caps (unfortunately, only one pair each) that allow the microphones to “get stuck” inside the ear canal, while protecting against gusts of wind and unwanted impacts.

A flexible and durable material-sheathed flat cable with two MicroDot connectors emerges from the handle. This solution was chosen to operate a microphone with a miniature DPA MMA-A interface that can be connected directly to the iPhone, to which we can record at 24-bit resolution and 114 dB dynamic range. The whole system can be installed and organized in such a way that, while maintaining complete freedom of movement, we become a mobile spatial stereo recording system.

On practice

By using CORE technology, which reduces the noise level (compared to standard solutions) by 14 dB, the microphones of the system are not only significantly less noisy, but also have high sensitivity, adjustable in the range of 30 dB in the DPA MMA-A application. There you can also turn on the high pass filter and decide whether you are working in stereo or dual mono.

The interface can also be connected directly to a PC or Mac, where it communicates as a d:vice MMA-A stereo port, offering up to 96kHz sampling and 24-bit resolution. Since the entire system is designed for mobile operation, the option of interacting with a computer should be considered as an auxiliary or backup option.

One thing needs to be clarified - these microphones are not headphones, so there is absolutely no question of any monitoring of the recorded signal, even by a person with microphones in their ears. Another thing is the sound nature of the recording, usually binaural. This means that we will get the best sound only when listening to it with headphones. When listening to loudspeakers, you will need to apply an inverted HRTF (Head Related Transfer Function) correction, which can be easily done with a three-parametric filter equalizer (see HRTF Curve inset).

With very sensitive microphones in your ears, you have to take into account that any blows to the cables, scratching on the head, grunting and other similar sounds will also be recorded. Unlike a microphone stand, we are living beings. My advice: a thin hat covering the ears. The sound does not change dramatically, and the position of the microphones in the ear canals becomes more stable, which reduces the risk of mechanical damage.

You can find some test recordings made with the DPA 4560 CORE Binaural on the Estrada and Studio podcast page: https://soundcloud.com/estradaistudio). They are designed to be listened to with headphones and only then retain their optimal character.

HRTF Curve

Binaural recordings are made in terms of playing them through headphones. Played with loudspeakers, they will be distorted in sound, because they are based on a different concept of sound reception - not in the so-called free field, but directly from the ear canal of the person hearing the sound. This sound, compared to open field sound, is processed in frequency and phase due to acoustic phenomena due to the size and shape of the head and pinnae, the distance between the ears, and even the presence and shape of the torso. These elements affect the specific filtering of sound before it reaches our hearing organ.

The characteristics of the equalizer setting to be applied to the signal if you want to play binaural recorded material through your speakers. This characteristic is approximately the reverse of the HRTF curve.

By studying these phenomena, a generalized characteristic of the influence of our physicality on the way of hearing was created, which was called the Head-Related Transfer Function (HRTF). So if we are recording sound through in-ear microphones (in theory, recording what reaches the inner ear), then if you want to play it back on speakers, you need to apply a correction that works inversely with the HRTF response. The applied correction is based on three filters. With a low shelving filter, the band should be raised 2 dB below 480 Hz; for 4 kHz, we use a band-pass filter with Q = 1, attenuating the signal by 11 dB; and for 8 kHz we turn on the band-pass filter with Q=2, increasing this range by 8 dB. This filtering should be introduced simultaneously in both channels.

HRTF curve obtained by comparing the measurement of the pink noise signal in the so-called free field with the measurement made with the same microphone, but placed in the ear canal. In both cases it was the DPA 4066 omnidirectional microphone. Photo: DPA

Of course, the described correction is not mandatory and is applied only when we intend to simulate the sound on the speakers, suitable for playback in headphones. In some situations, it may even turn out that the binaural recording will have a character that suits us without the need to apply just such a correction. For example, you can limit yourself to only the shelving attenuation of frequencies above 4 kHz by about 6 dB. 

Summation

The DPA kit is not cheap - we will pay a cutthroat PLN 4750 for the binaural microphone and PLN 2450 for the interface. For the latter, there is no reasonable alternative, because only then do we have a suitable small device with high enough quality and the presence of MicroDot inputs. Any other decision would be an impromptu and inevitable disaster during the recording.

The sensitivity of microphones, one of their biggest advantages, is also one of the downsides in terms of how they work. With them in our ears, we cannot expect the recording to be perfectly clear in every way, because we have to breathe, swallow, and sometimes scratch our heads, moo or sniff. The microphones are omnidirectional, so they readily pick up all these sounds.

However, I think that all the benefits of binaural technique are definitely worth spending some time removing noise in a good spectral editor like iZotope RX7. The space that we get in such a recording is unattainable for any other microphone technique, not to mention the means of virtual spatiality. Things happen at the level of micro-details, perfectly interpreted by our brain, which cannot be emulated by any means known today.

All this allows us to make an unambiguous conclusion that this is a product for professionals who want to move away from the accepted patterns in their work and start exploring completely new areas. The system may also be of interest to musicians and producers looking for non-standard recording methods. Although there are cheaper products on the market (Roland CS-10EM, Hooke Audio Verse or Soundman), they are quite far from the DPA 4560 CORE Binaural + MMA-A set in terms of functionality, parameters and workmanship.