Klark Teknik DN370 Dual Graphic Equaliser
The Klark Teknik DN370 is a dual thirty (30) band, third octave graphic equaliser designed to meet the needs of demanding live, recording, and broadcast sound engineers. It utilises premium quality, low tolerance components to achieve a high degree of accuracy and control. The DN370 is an addition to the world-renowned DN300 series of Graphic Equalisers and represents the next generation of graphic equaliser technology. The unit comes with a standard Klark Teknik three-year warranty.
Important Safety Instructions
Please read and keep these instructions. Heed all warnings and follow all instructions.
- Do not use this apparatus near water.
- Clean only with a dry cloth.
- Do not block any ventilation openings. Install in accordance with manufacturer's instructions.
- Do not install near heat sources.
- Do not defeat the safety purpose of the polarized or grounding-type plug.
- Protect the power cord from being walked on or pinched.
- Only use attachments/accessories specified by the manufacturer.
- Unplug during lightning storms or when unused for long periods.
- Refer all servicing to qualified personnel.
The following symbols are internationally accepted symbols warning of potential hazards with electrical products:
- Warning: Risk of Fire or Electric Shock. Do Not Open. (Indicated by a lightning flash with arrowhead symbol within an equilateral triangle, warning of uninsulated "dangerous voltage".)
- Caution: Risk of Electric Shock. Do Not Open.
- Avis: Risque de Choc Electrique. Ne Pas Ouvrir. (French for: Notice: Risk of Electric Shock. Do Not Open.)
- Exclamation point within an equilateral triangle: Indicates important operating and maintenance instructions.
Declaration of Conformity
Klark Teknik Group (UK) Plc, Klark Teknik Building, Walter Nash Road, Kidderminster, Worcestershire, DY11 7HJ, declares that the Klark Teknik DN370 Analogue Graphic Equaliser, when tested with a sample, is in conformity with the following directives and standards:
- 89/336/EEC Electromagnetic Compatibility Directive (amended by 92/31/EEC & 93/68/EEC)
- 73/23/EEC Low Voltage Directive (amended by 93/68/EEC)
- Generic Standard Using EN55103 Limits and Methods
- Class B Conducted Emissions Pavi
- Class B Radiated Emissions Pavi
- Fast Transient Bursts at 2kV
- Static Discharge at 4kV
- Electrical Stress Test
- Electrical Safety
This declaration was signed by Simon Harrison, Authority: Research and Development Director, Klark Teknik Group (UK) Plc, on 31st March 2004.
Attention: Specifiers, purchasers, installers, or users should observe special limitations of use for compliance with the above directives. Details are available on request.
Features
Front Panel
The front panel features:
- 30 Bands of Graphic EQ: Thirty (30) third-octave frequency bands with 45mm long-throw faders for precise adjustment. Faders have centre detents for 0dB (unity gain) indication.
- Gain Control: Provides continuous adjustment from -infinity to +6dB, with a centre detent at 0dB. This can be used to make up for EQ cuts or boosts.
- Range Switch: Allows switching the fader range between ±6dB and ±12dB for each channel, indicated by '6' and '12' LEDs.
- EQ IN/OUT Switch: Bypasses the graphic equaliser and gain control settings, allowing comparison with the original signal. Illuminated LEDs indicate status.
- Metering: Two LEDs per channel: Signal (Green, -40dBu) indicates incoming signal (Pre EQ, post Gain), and Clip (Red, +22dBu) indicates maximum output level and clipping (Post EQ, post Gain).
- Filters: Each channel includes one High Pass Filter, one Low Pass Filter, and two variable frequency Notch Filters. Filters are enabled by pushing the control knob, indicated by an illuminated ring.
- Power Switch: Located on the front panel, with an associated power indicator LED.
Rear Panel
The rear panel provides audio and power connections:
- Mains Supply: A single fused IEC type connector accepts 100-240V AC (50-60Hz, 60W). The unit features an auto-voltage sensing switching mode power supply. The correct mains lead for the region of shipment is supplied. Always replace the fuse with the same type and rating (e.g., T0.5A L250V).
- Audio Connections:
- Two male XLR inputs and two female XLR outputs for channels A and B (electronically balanced).
- Two 6-pin Phoenix connectors for channel A and B inputs/outputs (balanced audio).
- Pin Assignments (XLR & Phoenix): Pin 1: Screen/Ground, Pin 2: Hot Signal, Pin 3: Cold Signal.
- Transformer Isolation: Optional transformer isolation can be fitted for inputs and outputs.
Installation and Connections
Power Connection
Ensure the power supply is connected to ground via the ground in the mains connector for safety and electromagnetic compatibility.
Audio Connections
Use high-quality twisted-pair audio cables. XLR connector shells should be metal for screening and have pin one connected to the cable screen.
Electric Fields
Operation in strong, amplitude-modulated electromagnetic fields may degrade the signal-to-noise ratio.
Installation
Mount the DN370 in a 19-inch rack. Position it to avoid accidental operation of faders or the power switch. Avoid placing it near power distribution units or power amplifiers.
After Unpacking
Retain original packing for potential transport or shipping. Inspect the unit for any signs of transit damage and notify the courier immediately if damage is found.
System Connection Example
The DN370 can be integrated into various audio systems. A typical setup involves connecting the DN370 between a console (FOH or Monitor) and crossover/amplifier stages feeding loudspeakers. The diagram illustrates connections for Front of House (FOH) systems, including main outputs and delay outputs, and for monitor systems, including stage monitors and centre clusters. It also shows the potential use of a delay line.
Using the DN370
Studio and Creative Use
In a studio control room, the DN370 can be used to correct room acoustic deficiencies, often in conjunction with a Real Time Analyser (RTA) like the Klark Teknik DN60 or DN6000. Its ISO standard frequency centres align with RTAs for easy visual correction. It can also be used for creative filter effects, such as simulating a telephone voice, or as a de-esser when paired with a compressor. However, it cannot overcome severe acoustic problems or long reverberation times.
Live Use (Front of House)
For live sound (Front of House), the DN370 can correct venue frequency deficiencies. Using an RTA and measurement microphone is recommended for setup, focusing on attenuating peaks rather than boosting dips to maintain headroom. Excessive boost, especially at low frequencies, can lead to amplifier clipping, driver damage, and unpleasant sound. High-frequency boost may also reduce loudspeaker lifespan.
Live Use (Monitors)
On stage, the DN370 helps remove peaks in monitor frequency response to prevent feedback. Engineers can use an RTA or their hearing to identify and eliminate feedback frequencies. The unit's 30 bands and two notch filters allow precise removal of resonances and feedback. High and low pass filters can reduce rumble, high-frequency noise, and control bass levels for clarity and to prevent over-excursion of bass drivers.
Equalising a System
The primary benefits of equalisation are to improve intelligibility, natural sound, and increase system gain before feedback.
When equalising a system, it's important to first check its performance without EQ, potentially using sine tone sweeps to identify specific frequency issues. Use a calibrated measurement microphone placed in a sensible location. With an RTA and pink noise, adjust the graphic equaliser bands inversely to the RTA display to reduce peaks and increase dips, ensuring measurements are taken at normal operating volumes. Be aware that excessive EQ may indicate underlying system or acoustic problems and can strain amplifier headroom or loudspeaker drivers.
The equaliser is a tool to enhance sound quality, not a solution for fundamentally flawed systems or acoustics.
Effect of Equalisation on Voice and Music Reproduction
Voice Reproduction
| 1/3 Octave Centre Frequency | Effect on voice |
|---|---|
| 40, 50, 63, 80, 100, 125 Hz | Sense of power in some outstanding bass singers. |
| 160, 200, 250 Hz | Voice fundamentals. |
| 315, 400, 500 Hz | Important for voice quality. |
| 630, 800, 1k Hz | Important for voice naturalness. Excessive boost in this range can produce a telephone-like quality. |
| 1k25 to 4k Hz | Vocal fricatives, accentuation, and clarity. Important for speech intelligibility. Excessive boost can mask sounds or cause listener fatigue. |
| 5k, 6k3, 8k Hz | Accentuation and clarity of voice. Excessive boost can cause sibilance. |
| 10k, 12k5, 16k Hz | Cymbals and overall brightness. Excessive boost can cause sibilance. Reduction can reduce tape hiss and system noise. |
Music Reproduction
| 1/3 Octave Centre Frequency | Effect on Music |
|---|---|
| 31, 40, 50, 63 Hz | Fundamentals of bass drum, tuba, bass and organ. Can add power but excessive use can make sound 'muddy'. Also relates to mains hum (50-60Hz). |
| 80, 100, 125 Hz | Produces 'boom'. Fundamentals of tympani & toms. Higher harmonics of mains hum (100-120Hz). |
| 160, 200, 250 Hz | Drum and lower bass. Produces 'boom'. 3rd Harmonics of Mains Hum. |
| 315, 400, 500 Hz | Fundamentals of strings and percussion. |
| 630, 800, 1k Hz | Fundamentals and harmonics of strings, keyboards, percussion. Boosting can make instruments sound horn-like. |
| 1k25 to 4k Hz | Drums, guitar, vocals, strings, brass. Excessive boost can make instruments sound 'tinny' or cause listening fatigue. |
| 5k, 6k3, 8k Hz | Accentuation of percussion, cymbals, snare drum. Reduction can make sound more distant and transparent. Governs overall clarity and definition. |
| 10k, 12k5, 16k Hz | Cymbals and overall brightness. Reduction can reduce tape hiss and system noise. |
Functional Block Diagram
The DN370's signal path for a single channel includes:
- Input
- Gain Control
- High Pass Filter
- Graphic Equaliser (30 bands)
- Notch Filter 1
- Notch Filter 2
- EQ IN/OUT Bypass Switch
- Output
The diagram shows these stages connected sequentially. It also indicates the location of optional transformer isolation links.
The DN370 Proportional-Q Response
The DN370 utilises a Proportional-Q equalisation response, which differs from Symmetrical-Q equalisers. Proportional-Q offers advantages where filter width becomes narrower as boost/cut increases, providing a more 'focused' response. This allows for more precise control of problem frequencies without affecting as wide a spectrum as Symmetrical-Q.
Comparison with Symmetrical-Q:
- Symmetrical-Q (Wide/Narrow): For small adjustments (±2dB), the response is smooth. However, for full boost/cut, the affected frequency band becomes significantly broader, leading to less precision.
- DN370 (Proportional-Q): Provides a smooth response for small adjustments, similar to Symmetrical-Q's wide mode. Crucially, as boost or cut increases, the filter becomes narrower, offering superior precision for targeting specific problem frequencies. Extensive listening tests were conducted to achieve an optimum, musical-sounding response.
The DN370 also features sweepable high-pass, low-pass, and two notch filters. These filters have push-on/off bypass switching, indicated by illuminated rings. These filters enhance the unit's ability to surgically remove resonances and feedback, and tailor frequency extremes, making them particularly useful for monitor applications.
Applications
Front-of-House (FOH)
The DN370's filters provide subtle tonal correction with minimal ripple. Its Proportional-Q response allows for tightly-focused cuts to combat acoustic feedback. Range switching (±6dB/±12dB) and 45mm faders offer excellent control. Sweepable high-pass and low-pass filters match frequency extremes to loudspeaker capabilities, freeing up graphic EQ faders for acoustic management. Twin sweepable notch filters effectively suppress room resonances with minimal impact on the program material.
Monitors
The DN370's filters are designed for precise attenuation of problem frequencies in monitor systems to combat feedback. Long-throw faders provide detailed control, even with 12dB of attenuation. The unit's two sweepable notch filters allow surgical removal of resonances and feedback. Push switches with illuminated rings provide easy filter bypass. High and low pass filters control frequency limits for each output, beneficial for both wedge and in-ear monitors.
Examples of EQ Applications
The DN370's versatile filter set allows for precise control of frequency response in real-world corrective EQ scenarios:
- Notch Filter Precision: A single notch filter can precisely cut a specific frequency (e.g., 900 Hz), unlike Symmetrical-Q which affects a broader band, even when using its narrow response.
- Combined Filter Responses: The DN370's Proportional-Q faders, combined with notch filters, can create deep notches (up to 45dB attenuation) and tailored shelf responses with greater precision than Symmetrical-Q equalisers.
- Monitor EQ: High-pass, low-pass, and notch filters can be used to shape monitor wedge responses, remove specific feedback frequencies, and provide a cleaner sound, outperforming Symmetrical-Q equalisers in similar applications.
- High-Pass Functionality: Unlike Symmetrical-Q equalisers that rely solely on faders for low-frequency attenuation, the DN370's dedicated high-pass filter provides true subsonic frequency control.
Technical Specification
| Parameter | Specification |
|---|---|
| Inputs | Two, Electronically balanced (pin 2 hot) |
| Impedance | 20k Ohms |
| Max input level | +22dBu |
| Outputs | Two, Electronically balanced (pin 2 hot) |
| Minimum load impedance | 600 Ohms |
| Source impedance | <60 Ohms |
| Maximum output level | +22dBu >2k Ohm |
| Performance | |
| Frequency response (EQ out) | ±0.5dBu, 20Hz-20kHz relative to signal at 1kHz |
| Frequency response (EQ in, flat) | ±0.5dBu |
| Distortion (THD+N) | < 0.003% @ 1kHz, +4dBu |
| Dynamic range | >114dB (20Hz-20kHz unweighted) |
| Overload indicator | +20dBu |
| Gain | Infinity to +6dBu |
| Equalisation | 30 Bands |
| Centre Frequencies | To BS EN ISO 266:1997 25Hz-20kHz, 1/3 octave |
| Tolerance | ±5% |
| Maximum Boost/Cut | ±12dB, ±6dB |
| High Pass Filter Slope | 12 dB/octave |
| Low Pass Filter Slope | 12 dB/octave |
| Notch filter | Attenuation >18dB, Q=32 |
| Terminations | 3-pin XLR and 6-pin Phoenix |
| Power Requirements | |
| Voltage | 100V-240V a.c. |
| Consumption | <60W |
| Dimensions | |
| Height | 133mm (5.25 inch) - 3U High |
| Width | 482mm (19 inch) |
| Depth | 205mm (8 inch) |
| Weight | |
| Nett | 5.6kg |
| Shipping | 7.0kg |
| Options | Input and output balancing transformer |
BS EN ISO 266:1997 Frequency Centres: 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800 Hz, 1.00 kHz, 1.25 kHz, 1.60 kHz, 2.00 kHz, 2.50 kHz, 3.15 kHz, 4.00 kHz, 5.00 kHz, 6.30 kHz, 8.00 kHz, 10.0 kHz, 12.5 kHz.
Klark Teknik Group reserves the right to alter specifications without notice.
Frequency Chart
This chart provides a guide to the fundamental frequency ranges of common musical instruments and voice types across the audible spectrum (25 Hz to 20 kHz). It maps these ranges against the DN370's third-octave frequency bands. The chart also indicates the typical ranges for the DN370's High Pass Filter, Low Pass Filter, and Notch Filters.
Instruments covered include: Piano, Large Pipe Organ, Violin, Viola, Cello, Double Bass, Bass Drum, Snare & Toms, Piccolo, Flute, Oboe, Bassoon, Trumpet, Trombone, Tuba, Soprano, Contralto, Baritone, Bass, Drum Kit (Bass Drum/Snare+Toms), and Guitar.
A=440Hz is noted as a reference point.
Crib Sheet
The crib sheet is a template designed for users to record their specific settings for the Klark Teknik DN370. It includes fields for Date, Location, and Application for each channel (A and B). The layout visually represents the front panel controls, allowing users to mark the positions of faders and switches for future reference or recall.
