Line array condenser Microphone System KEM 975 – the high-end Allrounder with non-rotation-symmetrical polar pattern

The KEM is ideally suited for musical applications, for example for recordings in the Leipzig Gewandhaus, the State Opera and Konzerthaus Berlin, the Cologne Opera, the Bonn Theater and in many others.

The 16th ST.GALLEN FESTIVAL 2021 – Best sound performance thanks to high-quality Microtech Gefell microphones

The highlite has been the opera “Notre Dame” by the composer Franz Schmidt. Due to corona restrictions  the orchestra and the Prague choir had to be transmitted by fibre optics from the theatre’s concert hall to the open-air venue in the cloister courtyard. The responsible sound engineers  Stephan Linde (choir /soloists) and Benjamin Schultz (orchestra) underlined, that the used for the transmission cardioid plane mics KEM 975 ideally kept the crosstalk between orchestra and choir to a minimum.

The fine difference – KEM 975 with a delta capsule

The KEM 975 with a delta capsule,  is ideally suited for musical applications, for example for recordings in the Leipzig Gewandhaus, the State Opera  and Konzerthaus Berlin, the Cologne Opera, the Bonn Theater and in many others.

Below approx. 800 Hz, the KEM 975 cannot maintain its clubbed directivity in the vertical plane anymore due to its length and approaches a cardioid polar pattern more and more with decreasing frequency. With a process developed and patented by the Institut für Rundfunktechnik München  (Institute for Broadcasting Technology Munich), the directivity and the directionality are increased in this frequency range by using the optional attachable Delta capsule which forms an equilateral triangle together with the two outermost capsules of the KEM 975. Thus, a frequency-constant directivity index is realised across the entire frequency range down to below 100 Hz. The result is a better spatial separation of sound sources with low-frequency signal portions and a more consistent spaciousness in the recorded signal over the frequency spectrum. This is particularly advantageous for music recordings

KEM 975 – the high-end Allrounder – High sound quality for conference presenters, speaker, studio, TV and broadcast

If the KEM 975 is used as a speaker’s microphone on a lectern or desk, it can be used without the Delta capsule, as speech frequencies are above the threshold where the Delta capsule is needed.

A significant advantage for speakers and presenters  is the non-rotationally symmetric directional distribution, which provides an extremely large freedom of movement of the speaker in the horizontal plane with an extreme suppression of disturbing noise in the vertical plane.

The KME 975 has a directional distribution of sensitivity, which is not rotationally symmetric to the reference axis. The designation “cardioid plane microphone” results from this special directional distribution (flat cardioid).

Ein wesentlicher Vorteil für die Redner ist die die  nicht rotations-symmetrische Richtcharakteristik, die eine extrem große Bewegungsfreiheit des Sprechers in der horizontalen Ebene bei einer extremen Unterdrückung von Störschall in der vertikalen Ebene bewirkt.

Especially important in Corona times –  Video conferences and workshops, online-meetings and presentations

In times where due to the pandemic fairs, business trips, meetings with partners and customers, presentation events etc. are not possible, it is even more important to look for alternatives to stay present on the market.

Virtually all physical in-person events have been canceled or postponed for the foreseeable future.

Nevertheless  companies still have a need to engage with and get in front of market- decision makers, while remaining safe, socially distant, and healthy.

So how do you that  – by running Virtual Events.

In the current situation Virtual Events are the best way to communicate with partners, suppliers, specialists  or clients.

Video and on-line communication plays a key role in this process, provided that there are no sound problems.

An ideal tool for the best sound in video conferences is the KEM 975 cardioid plane microphone due to its special features, such as:

– Detection of widely spread or moving sound sources

– optical display for optimal recording range

– latency-free analog signal processing

By the way – When you factor in the costs of exhibiting at a trade show compared to that of a virtual event, the costs per virtual event are dramatically lower.

KEM 975 – Best sound quality in Parliaments

In the meantime, the KEM 970 or its more compact successor model, the KEM 975, is also used in state parliaments and parliaments abroad, e.g. in the German state of Thuringia, but also in Hesse, Baden-Württemberg, North Rhine-Westphalia, Poland, Turkey, etc.

KEM 970 / KEM 975 – Short Summery

The cardioid plane microphone KEM 970 and the successor KEM 975 are a line array microphone system with a largely frequency-independent polar pattern, which – in the horizontal plane – has the features of a cardioid microphone and – in the vertical plane – the features of a directional microphone with an operating angle of approx. 30 degrees. Thus, the polar pattern is adapted to the frequent case that the sound source to be captured is wide in space or moves around in it and, at the same time, sound coming from other directions is to be suppressed. The sound to be rejected may consist of disturbing noises or reflections which come from the ceiling, table surfaces or floor areas. Due to its directional characteristics, the KEM 975 can be used for recording sound sources that are very extensive in width and depth or moving sound sources. Since the complete signal processing is analogue, there are no signal delays.

Acoustic properties

The KME 975 has a directional distribution of sensitivity, which is not rotationally symmetric to the reference axis. The designation “cardioid plane microphone” results from this special directional distribution (flat cardioid). Regarding the polar pattern, the KEM 975 has – in the horizontal plane – the features of a cardioid microphone with an opening angle of 120 degrees and – in the vertical plane – the features of a directional microphone with an opening angle of 30 degrees. Due to signal processing adjusted to the capsule positions, the vertical 30˚ opening angle remains constant above approx. 800 Hz over the whole upper frequency range.

The high directional selectivity of the microphone requires knowledge of the directions of incidence of useful sound and disturbing noise. The more carefully the KEM 975 is adjusted accordingly, the better the achieved results. The optimum adjustment is facilitated by an LED position indicator, which can be switched off and is attached inside the protective grille.

Eight high quality small-membrane condenser capsules of the M 300/ M 21 series with a gold-sputtered polyester membrane are used as the sound transducers. The amplitude-frequency response of the KEM 975 shows an increase of 2 dB between 2 kHz and 12 kHz to increase the speech and high-frequency intelligibility.

The optional Delta capsule, which can be plugged into the KEM 975, effects an increase of the directivity and directionality in the frequency range below approx. 800 Hz whereby the directivity index of the KEM 975 with attached Delta capsule has an almost constant frequency directivity of 9 dB even with lower frequencies down to below 100 Hz. The Delta capsule is automatically recognised by the KEM 975 and the signal processing is adjusted accordingly. Even if a delta capsule is plugged in, the complete signal processing remains analogue and thus latency-free.

If the KEM 975 is installed and aligned properly, sensitivity is reduced as the sound source comes closer to the microphone. The sound source with the longest distance is in the range of maximum sensitivity. As a sound source comes closer to the microphone, it leaves the area of maximum sensitivity. In this way, the level increase caused by approaching the sound source is compensated for. By careful positioning and angle setting, the intensity of this compensation can be varied.