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The DN370 is the latest evolutionary step in a process of design refinement that goes back over 40 years to the earliest Klark Teknik graphic equalisers. The enhanced Proportional-Q response recaptures that of the classic single channel DN27 graphic equaliser using modern solid-state design and manufacturing technologies, and the DN370 features dual channel 30 band graphic equalisation with swept high-pass and low-pass filters and two swept notch filters per channel. This highly flexible tool box of corrective equalisation and filtering is ideal for both Front of House and stage monitoring applications, where both the gentle contouring and surgically precise high-Q notches uniquely made possible by the Proportional-Q response enhance intelligibility as well as eliminating sub-sonic rumble, room and speaker resonances and standing waves. DN370 is designed for system installers as well, and features Phoenix-style connectors for ease of installation.
Klark Teknik's enhanced Proportional-Q equalisation offers key advantages over the more numerous Constant-Q graphic equalisers on the market. A Constant-Q response boosts or cuts an increasingly wide band of frequencies, resulting in more of the frequency spectrum being lost when using a Constant-Q equaliser to eliminate problem frequencies. If the response of a Constant-Q equaliser is made narrower to compensate, the result is ripple in the frequency response when small amounts of boost and cut are applied.
In contrast, with a Proportional-Q response, at low amounts of cut or boost the width of the filter is relatively broad allowing for gentle contouring of the frequency spectrum, but becomes progressively narrower as the amount of boost or cut is increased, giving a more ‘focused' response ensuring that problem frequencies can be attenuated quickly and effectively. At the same time, the enhanced Proportional-Q equalisation response used on DN370 minimises interaction between adjacent frequency bands, allowing subtle tonal correction without frequency response ripple, so that more of the musical content is preserved.
DN370 augments the Proportional-Q graphic equalisation section with a comprehensive set of continuously swept filters for precise corrective control of the audio spectrum. The control knobs incorporate a push function to switch the filter in and out whilst maintaining the frequency setting, and feature illuminated LED rings for ‘at a glance' status display, even at wide distances and viewing angles.
The 12 dB/oct high-pass filter features a 20 Hz to 500 Hz range and is invaluable for the smooth rejection of unwanted low and subsonic frequencies, particularly relevant for use with modern compact wedge monitors. The 12 dB/oct low-pass filter features a 2 kHz to 20 kHz range and can be used to improve intelligibility by tailoring the upper frequency response to match that of the monitor speaker.
The two notch filters feature overlapping frequency ranges of 20 Hz to 2 kHz and 200 Hz to 20 kHz. The notch filters allow the surgical removal of resonances and feedback with minimal effect on the rest of the program material, and fast control of ‘between fader' frequencies. The ability to overlap the notch filters, both with each other and with the graphic equaliser bands, allows very deep notches to be created. Up to 45 dB of attenuation is possible when using the notch filters in conjunction with the graphic equaliser bands.
A channel gain control is provided with range from -? to +6 dB. In the event of sudden on-stage feedback, this control can be used to immediately mute the signal path whilst the cause is established.
The DN370 graphic equaliser section features centre-detented long-throw 45 mm precision oil-damped faders which allow a high degree of control over the ±12 dB range, and a ±6 dB range is also provided for increased resolution for even finer control of the audio frequency spectrum response. Channel bypass and graphic equaliser range selection switches are also provided for easy configuration and comparison of the graphic equaliser setting with the direct signal. The faders also feature protective covers to inhibit the ingress of dirt and dust, to maximise their working life in demanding environments.
DN370 has electronically-balanced inputs with excellent common-mode rejection and the electronic servo-balanced outputs have high-drive capability to cope with long cable runs. Although equalisers are more generally used on console inserts, the DN370 is fully capable of being used in-line with cables running the long distances between the Front of House mix position, the main stage and the delay towers in festival PA systems. Power-off bypass relays preserve the signal path in the event of a power failure, and the recessed front panel power switch is designed to avoid accidental operation.
Transformer balancing is available as an additional option on both the inputs and outputs.