DN370

OPERATORS MANUAL

Klark Teknik Group,

Klark Teknik Building,
Walter Nash Road,
Kidderminster,
Worcestershire,
DY11 7HJ
England

Tel: +44 (0) 1562 741515

Fax: +44 (0) 1562 745371

Email: sales@ktgplc.com
Website: www.klarkteknik.com

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 IMPORTANT SAFETY INSTRUCTIONS

CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN

WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK,

DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE
AVIS: RISQUE DE CHOC ELECTRIQUE. NE PAS OUVRIR

These symbols are internationally accepted symbols that warn of potential hazards
with electrical products.

The lightning flash with arrowhead symbol, within an equilateral triangle is

intended to alert the user to the presence of uninsulated “dangerous
voltage” within the product's enclosure that may be of sufficient magnitude
to constitute a risk of electric shock to persons.

The exclamation point within an equilateral triangle is intended to alert the

user to the presence of important operating and maintenance (servicing)
instructions in the literature accompanying the appliance.

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any of the ventilation openings. Install in accordance with the manufacturers
instructions.

8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus
(including amplifiers) that produce heat.

9. Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding type plug has two blades and a third grounding
prong. The wide blade or the third prong are provided for your safety. If the provided plug does not fit
into your outlet, consult an electrician for replacement of the obsolete outlet.

10. Protect the power cord from being walked on or pinched particularly at plugs, convenience
receptacles, and the point where they exit from the apparatus.

11. Only use attachments / accessories specified by the manufacturer.

12. Unplug this apparatus during lightning storms or when unused for long periods of time.

13. Refer all servicing to qualified personnel. Servicing is required when the apparatus is damaged in any
way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into
the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has
been dropped.

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 Klark Teknik Group (UK) Plc, Klark Teknik Building, Walter Nash Road,
Kidderminster. Worcs. DY11 7HJ. England
Tel:+44 1562 741515 Fax:+44 1562 745371
www.midasconsoles.com www.klarkteknik.com

DECLARATION OF CONFORMITY

We, Klark Teknik Group (UK) Plc

of, Klark Teknik Building, Walter Nash Road, Kidderminster, Worcestershire, DY11 7HJ.

Declare that a sample of the following product:-

Product Type Number Product Description Nominal Voltage (s) Current Freq
DN370 Analogue Graphic 115V AC 240mA 50/60Hz
Equaliser 230V AC 120mA

to which this declaration refers, is in conformity with the following directives and/or 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 EN50081/1
Class B Conducted Emissions Pavi EN55103
Class B Radiated Emissions Pavi EN55103
Fast Transient Bursts at 2kV EN61000-4-4
Static Discharge at 4kV EN61000-4-2
Electrical Stress Test EN60204
Electrical Safety EN60065:2002

st
Signed:............................ Date:31 March 2004
Name: Simon Harrison

Authority: Research and Development Director, Klark Teknik Group (UK) Plc

Attention!
Where applicable, the attention of the specifier, purchaser, installer or user is drawn to special limitations
of use which must be observed when these products are taken into service to maintain compliance with
the above directives. Details of these special measures and limitations to use are available on request
and are available in product manuals.

Company registration No. 2414018. A Subsidiary of Telex Communications Inc.

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 Thank you

Thank You for using a Klark Teknik DN370 Graphic Equaliser. The DN370 has been developed to meet the needs of
demanding live, recording and broadcast sound engineers and meets the quality in build and performance that you
would expect from Klark Teknik.

The DN370 is a dual thirty(30) band third octave graphic equaliser with long throw forty-five millimetre (45mm)
faders, two (2) high and low pass filters per channel and two (2) notch filters per channel. The DN370 is the latest
addition to the world renowned DN300 series of Graphic Equalisers that are in use around the world today and
represents the next generation of graphic equaliser technology.

All backed up, of course, by the standard Klark Teknik three year warranty.

Please take the time to complete and return the registration card and, to obtain the best results with a minimum of
effort, also read this operators manual.

Finally, enjoy your Klark Teknik DN370!

Contents

ATTENTION Page 2

Quick Reference
Front Panel Page 3
Rear Panel Page 4

Features
Front Panel Page 5
Rear Panel Page 7

System Example Page 9

Using the DN370 Page 10

Equalising a System Page 11
The effect of equalisation Page 12

Functional Block Diagram Page 13

The DN370 Proportional-Q response Page 14

DN370 Applications Page 17

Technical Specification Page 21

Frequency Rage Chart Page 22

Crib Sheet Page 23

DN370 Operators Manual - Page 1

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 ATTENTION

The following special limitations must be observed in order to maintain safety and electromagnetic compatibility
performance.
Power Connection Electric Fields

The DN370 Graphic Equaliser should only be operated with the If the DN370 is operated in an electromagnetic field that is
power supply connected to ground via the ground in the mains amplitude modulated by an audio frequency signal, the signal
connector. to noise ratio may be degraded. Degradation of up to 60dB
may be experienced under extreme conditions (3V/m, 90%
Audio Connections modulation).

The DN370 should only be operated with high quality twisted-

pair audio cables. XLR connector shells should be of metal
construction so that they provide a screen when connected to
the console and should have pin one (1) connected to the cable
screen.

INSTALLATION

Position

The DN370 should be mounted in a nineteen inch (19”) rack of suitable construction for it’s intended purpose. Four (4) rack
mount holes are provided through the front panel to support fully, the weight of the unit in the rack. Position of the unit will
depend upon how it is to be used however:-

- Avoid placing the unit such that the faders may be accidentally knocked or snapped off
- Avoid placing the unit such that the front mounted power switch may be accidentally knocked

Also try to avoid placing the unit directly near or on any power distribution units or power amplifiers.

Power

The internal power supply is a switch mode type which automatically senses the incoming mains voltage and will work where the
nominal voltage is in the range 100-240 VAC. A single fused IEC mains inlet is provided on the rear panel and the correct lead for
connection in the area to which the unit was shipped is provided in the box.

Connections

To ensure the correct and reliable operation or your DN370 Graphic Equaliser, only high quality balanced screened twisted pair
audio cable should be used.

Female XLR

Pin 1 - Screen/Ground
2 1 6 5 4 3 2 1
Pin 2 - Hot Signal
3 Pin 3 - Cold Signal

Male XLR Phoenix Type Connector

Pin 1 - Channel IN Screen/Ground
1 2
Pin 1 - Screen/Ground Pin2 - Channel IN Hot Signal
Pin 2 - Hot Signal Pin 3 - Channel IN Cold Signal
3 Pin 4 - Channel OUT Screen/Ground
Pin 3 - Cold Signal
Pin 5 - Channel OUT Hot Signal
Note: XLR Sockets are viewed from the Pin 6 - Channel OUT Cold Signal
front face.
Note: Pin assignments as viewed from the
socket. Phoenix connector is wired in parallel with
the corresponding XLR.

After Unpacking

After unpacking your DN370, please retain the original packing in the event that you should need to transport or ship the unit.
Please inspect the unit carefully for any signs of damage that may have occurred in transit and notify the courier immediately if
you feel that any damage has occurred.

DN370 Operators Manual - Page 2

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 The Klark Teknik DN370 is a dual thirty (30)
band, third octave graphic equaliser.

Equaliser bands
may be switched High and low
between 6dB pass filters per
45mm faders Level metering. and 12dB . channel.

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+6 +12

Channel
A

-6 -12

+6 +12
DN370 DUAL GRAPHIC EQUALISER

Channel
B

DN370 Operators Manual - Page 3

-6 -12

Equaliser in/out Notch filters Power switch

switch to bypass the per channel. and power
effect of the equaliser indicator.
Front panel quick reference
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CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN

WARNING: TO REDUCE THE RISK OF ELECTRIC SHOCK,

DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE
AVIS: RISQUE DE CHOC ELECTRIQUE. NE PAS OUVRIR.
NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO MADE IN KIDDERMINSTER, ENGLAND
QUALIFIED SERVICE PERSONNEL.

CAUTION: FOR CONTINUED PROTECTION AGAINST RISK OF

FIRE REPLACE WITH THE SAME TYPE AND VALUE FUSE INDICATED.
ATTENTION: REMPLACER PAR UN FUSIBLE DE MÊME TYPE
COMME INDIQUÉ.

THIS DEVICE COMPLIES WITH PART 15 OF THE FCC RULES. OPERATION IS SUBJECT TO THE FOLLOWING CONDITIONS:
(1) THIS DEVICE MAY NOT CAUSE HARMFUL INTERFERENCE, AND
(2) THIS DEVICE MUST ACCEPT ANY INTERFERENCE RECEIVED, INCLUDING INTERFERENCE THAT MAY CAUSE UNDESIRED OPERATION.

OUTPUT B INPUT B OUTPUT A INPUT A

SUPPLY PUSH PUSH
VOLTAGE

DN370 Operators Manual - Page 4

100-240V
AC~50-60Hz 60W INPUT TX
FUSE: 5x20mm
T0.5A L250A
R
OUTPUT TX
TO REDUCE RISK OF FIRE, REPLACE WITH SAME TYPE OF FUSE.
C US
MOUNT IN RACK ONLY

Fused IEC type Audio connections are Two six pin Phoenix
connector provided by two male XLR connectors
and two female XLR sockets
for channel A and B.
Rear panel quick reference
 Front panel features

Front Panel Features

The Klark Teknik DN370 is a dual thirty (30) band, third octave graphic equaliser. The range of the equaliser bands may be
switched between 6dB and 12dB (individually for each channel). In addition to the graphic equaliser itself; high and low pass
filters and two notch filters are provided per channel and an equaliser in/out switch to bypass the effect of the equaliser and filter
stages. Power to the unit is provided on the rear panel, but switched from the front. A power indicator is provided.

Metering

The DN370 provides two LEDs per channel for the purpose of level metering. The signal LED shows incoming signal to the unit
and is Pre EQ (but post gain control). The clip LED shows that the maximum output level of the unit has been achieved and the
unit has entered clipping. The clip LED is sourced Post EQ (and post gain control) such that internal clipping due to excessive EQ
(i.e. if a high input level is further boosted by the use of EQ) will also be shown. The clip and signal levels are shown below.

Signal (Green) -40dBu

Clip (Red) +22dBu

Graphic EQ Section

The graphic EQ section of the DN370 features long throw forty-five millimetre (45mm) faders to allow fine adjustment of each
frequency band. Each fader has a centre detent (’click stop’) to denote the 0dB (unity gain of the band) point of the scale. The
DN370 uses standard ISO third-octave standard frequency centres.

The range of the faders on each channel is switchable using that channel’s RANGE
switch between ±6dB and ±12dB. The current setting is indicated by the ‘6’ and
‘12’ LEDS above the range switch.
+6 +12
It may be desirable to hear the effect of the graphic equaliser settings (e.g. during
sound check). This can be achieved by depressing the EQ IN/OUT switch which will
bypass the EQ (and gain) settings of the DN370 allowing the user to hear the
original without adjusting any fader or control. The red and green LEDs indicate
whether the unit is bypassed or not.

Placing the fader of any band at the extreme upwards position will apply either
-6 -12 6dB or 12dB gain (depending upon the setting of the range switch) to the
frequencies in that band. Placing the fader of any band at the extreme downwards
position will apply either 6dB or 12dB attenuation (depending upon the setting of
the range switch) to the frequencies in that band.

Gain and Range Settings

GAIN

The gain control provides continuous adjustment of the channel gain from -infinity
(off) to +6dB with a centre detent at 0dB (unity gain). When using EQ with large
amounts of cut or boost, it may be necessary to use the gain to make up or
attenuate the signal. Note, however, that the gain control is bypassed when the EQ
IN/OUT switch is in the OUT position but control over the channel LEDs is retained
by the gain control.

RANGE

Although range is discussed above, a description is included here for clarity. The
range of the graphic equaliser section faders on each channel is switchable using
the RANGE switch between ±6dB and ±12dB. The current setting is indicated by
the ‘6’ and ‘12’ LEDS above the range switch.

EQ IN/OUT

The EQ IN/OUT switch will bypass all the functions of the DN370 including the Gain
control such that the output will be the same as the input. The IN/OUT switch may
be used to audition settings (for example, during sound check).

DN370 Operators Manual - Page 5

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 Front panel features

Signal Level

Signal - The signal LED shows incoming signal to the unit and is Pre EQ (but post
gain control).

Clip - The clip LED shows that the maximum output level of the unit has been
achieved and the unit has entered clipping. The clip LED is sourced Post EQ (and
post gain control) such that internal clipping due to excessive EQ (i.e. if a high
input level is further boosted by the use of EQ) will also be shown. The clip and
signal levels are shown below.

Signal (Green) -40dBu

Clip (Red) +22dBu

High Pass, Low Pass and Notch Filters

Each channel of the DN370 includes one (1) High Pass filter, one (1) Low Pass Filter and two (2) variable frequency Notch filters.
Each filter can be enabled by depressing the pot until it clicks (only a small amount of force is required). When active, the annular
ring around the filter control will illuminate.

To audition the effect of the filters, either the EQ IN/OUT switch (which will also bypass the graphic equaliser) or the individual
filter switch may be used.

Low Pass filter High Pass Filter

The cut off frequency is The Cut off frequency is
continuously variable from continuously variable from
20Hz to 500Hz 2kHz to 20kHz

Notch Filter 1 Notch Filter 2

The notch centre frequency The Notch filter centre
is continuously variable from frequency is continuously
20Hz to 2kHz variable from 200Hz to 20kHz

DN370 Operators Manual - Page 6

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 Rear panel features

Rear Panel Features

The rear panel provides the audio and power connections to the DN370.

Power is provided by a single fused IEC type connector. The correct mains lead for the country to which the unit was shipped is
supplied with the unit. Always replace the mains fuse with the same type and rating.

Audio connections are provided by two (2) male XLR and two (2) female XLR sockets for channel A and B inputs and outputs
respectively; and also by two (2) six (6) pin Phoenix connectors. Both connectors provide balanced audio connections such that:

Pin 1 - Ground/Screen
Pin 2 - Hot Signal
Pin 3 - Cold Signal

Mains Supply

SUPPLY Mains power is supplied to the DN370 by a single fused IEC socket on the rear of
VOLTAGE the unit. The DN370 contains an auto voltage sensing switching mode power
100-240V
AC~50-60Hz 60W supply that will operate where the nominal mains voltage is in the range 100 to
FUSE: 5x20mm 240 VAC.
T0.5A L250A
R

C US

Audio Connection

The audio connections to the DN370 are electronically balanced. Isolation transformers can also be fitted as factory option or
retro-fit (please consult an approved Klark Teknik service agent). The input and output connectors are shown below, please read
the audio connections section at the beginning of this manual for wiring diagrams and pin assignments.

OUTPUT B INPUT B
PUSH

INPUT TX

OUTPUT TX

Indicates whether the

transformer isolation input and
output options have been factory
fitted.
Channel Output XLR
Channel Input/Output Phoenix Connector
Channel Input XLR

DN370 Operators Manual - Page 7

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 DN370 Operators Manual - Page 8

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 Example: System connection

EQUALISER

X-Over &
Amplifiers

EQUALISER

X-Over &
Amplifiers

Centre Cluster

Delay FoH Delay FoH

Main FOH Main FOH

Stage Monitors

EQUALISER

X-Over &
X-Over & Amplifiers
Amplifiers

Monitor
Console
Delay Line

FOH Console

DN370 Operators Manual - Page 9

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 Using the DN370

The DN370 is a thirty (30) band third octave graphic equaliser which utilises premium quality, low tolerance components to
achieve a high degree of accuracy and control. Graphic equalisers may be used for corrective or creative purposes depending
upon whether it is to be used live (Monitors or Front of House) or in the studio (Broadcast or Recording).

Studio and Creative Use

In the control room, a graphic equaliser may be used to remove problem frequencies and improve deficiencies in room acoustics.
This is commonly achieved with the use of a Real Time Analyser (RTA) such as the Klark Teknik DN60 or DN6000. The frequency
centres of the DN60/6000 and the DN370 conform to ISO standards and so corrections can be made by sight directly from the
RTA to the graphic.

It is important to mention, however, that graphic equalisers can only compensate so much for a room with severe acoustic
problems (which may require further remedial treatment work). Graphic equalisers can only help to reduce the audible effects of
standing waves and resonances and cannot overcome the loss of clarity due to rooms with long reverberation times.

The DN370 can be used to create filter effects (for example the effect of someone speaking on the telephone) using the thirty (30)
equaliser bands and the high and low pass filter; in conjunction with a compressor to create a de-esser; for tonal correction of
instruments or vocals and many other creative uses.

Live Use (Front of House)

It is often desirable to add equalisation to a venue in order to remove any frequency deficiencies in the room before trying to
engineer using the system. Again, it is common to use an RTA and measurement microphone in order to set up the equaliser using
additive and subtractive equalisation to correct problems in the room. It is recommended to attenuate peaks in the room’s
response to the level of the surrounding frequencies rather than boost the lower bands to meet the highest. This will help to retain
headroom in the equaliser and slight dips in frequency response are less noticeable than large peaks. If an overall reduction in
volume is observed, the gain makeup can be used to return the output of the equaliser to the desired level.

Beware, however, that excessive equalisation (for example, using large amounts of boost at lower frequencies to compensate for
poorly performing bass enclosures) will use up large amounts of system headroom which could cause the system amplifiers to
clip. Causing damage to loudspeaker HF components and introducing high frequency harmonics which may sound unpleasant.
Also, large amounts of low frequency boost may cause the over-excursion of bass drivers and their subsequent mechanical and
electrical breakdown.

Also, many sound reinforcement systems are only capable of adequately producing frequencies up to around 18kHz. Providing
high levels of boost at 20kHz to extend the frequency response of the system is likely to result in reducing the life of high
frequency components in the loudspeaker while the frequency response may not be significantly improved.

There are occasions where deficiencies in room acoustics cannot be corrected by equalisation. For example, bass reduction due to
phase cancellation or the cancellation around the crossover point of a loudspeaker must be corrected before the use of
equalisation.

Live Use (Monitors)

Monitors used on stage often need equalisation to remove any peaks in their frequency response in order to prevent feedback
from on stage microphones where those frequencies exceed the maximum gain before feedback level. Further equalisation may
be required in order to remove similar peaks from the characteristics of the microphones in use.

A monitor engineer may use an RTA in order to detect these peaks, but more often than not, monitor engineers have a developed
sense of hearing that enables them to remove these frequencies by ear. The DN370’s thirty (30) frequency bands allow a majority
of feedback to be removed from the monitors, however, for feedback that is more difficult to locate or lies between bands, two
variable frequency notch filters are provided which can be swept through the frequency range until the location of the feedback is
located.

In addition to notch filters, a high and low pass filter are provided which can be used to remove high frequency feedback and bass
rumble or over excursion of bass drivers. It may also be undesirable to have large amounts of bass in the on stage monitors. In
vocal monitors, bass does not assist projection of vocals and can make the stage sound unbearable and hence, the bass element
can be rolled off at the desired frequency. The fundamentals of Vocals are transmitted in a narrow audible range and will appear
unaffected.

DN370 Operators Manual - Page 10

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 Equalising a system

As discussed before, the benefits of equalisation are fundamentally:-

To improve the intelligibility and natural sound of the sound system.

To increase the gain available in the system before feedback.

In some circumstances, it may not be possible to achieve a natural sounding system that is completely intelligible due to poor
acoustics or high levels of background noise. In these cases, a compromise must be struck by the engineer depending upon the
use to which the system will be put. It may be arguable that in the case of a vocalist, intelligibility must be sought at all costs. In
the case of dance music reproduction, however, it may be felt that the material should be reproduced naturally with no real
concern for intelligibility of the individual lyrics.

Before starting to equalise the system, it is worth checking that it is performing correctly. Listening to the system without any
equalisation may reveal underlying distortion or artefacts of the room (e.g. lengthy reverberation) that may need to be rectified
before trying to equalise the room. It may also be worth using a sine tone sweep so that problems at certain frequencies that may
not be immediately noticeable with pink noise can be detected and corrected before equalisation. Check, especially, the
crossover points of the system which may reveal problems with the system. Note that poor coverage cannot be rectified through
the use of equalisation.

The measurement microphone should ideally have a flat response or be calibrated to the analyser and placed in a sensible
position where it will not be affected by nearby objects that may interfere with the local acoustics.

Using the Real Time Analyser and a pink noise source, adjust the level of the frequency bands on the graphic inversely to that
shown on the RTA display so that the peaks in frequency response are reduced to the level of the other bands and similarly, the
deficient bands are increased. You will need to perform the test at a reasonable level approaching normal usage volume so that
the equalisation can take into account the response of the loudspeakers at normal operating level (vs. low level). It may also be
desirable to take measurements at points throughout the area. It may not be possible to get perfect equalisation throughout an
entire area but it may be preferable to obtain a good equalisation of the whole area rather than a perfect equalisation at a single
point and poor performance at all other points. A compromise may need to be made in an effort to equalise the sound for the
whole area rather than just the centre FOH position.




 

 


 





 

 



 





 

 


 





 

 



 


EQUALISER 
























 
 


 






 









 

 



 


CALIBRATED MEASUREMENT
MICROPHONE

l abc note: when using an RTA, ensure that

it has averaging capability so that fluctuations
PINK NOISE
are smoothed out giving a good representation
of the sonic performance of the system.
REAL TIME ANALYSER

When equalising the room, bear in mind the effect upon the electronics and mechanics of the system caused by the equalisation
process. If excessive equalisation is required at certain bands, consider the effect upon amplifier headroom and loudspeaker
driver excursion that will result. It may not be possible to produce the response required with the limitations of the system.
Excessive equalisation should act as a warning that there may be an underlying problem that may need to be rectified first (e.g.
phase cancellation, blown drivers, etc...).

During the performance, the FOH or monitor engineer may want to have a microphone or solo signal feed for the RTA so that
feedback may be easily detected and rectified.

Remember, the equaliser is not a ‘cure all’ device and will not solve the problems of a poor sound system, installation or venue
acoustics, but when used carefully, can bring out significant improvements in the quality of reproduction of a system.

DN370 Operators Manual - Page 11

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 Effect of equalisatiion

Effects of Equalisation on Voice Reproduction

1/3 Octave Effect on voice
Centre Frequency

40, 50, 63, 80, 100, 125 Sense of power in some outstanding bass singers

160, 200, 250 Voice fundamentals

315, 400, 500 Important for voice quality

630, 800, 1k Important for voice naturalness. Too much boost in the 315 to 1k
range produced a telephone-like quality

1k25 to 4k Vocal fricatives. Accentuation and clarity of voice

Important to speech intelligibility. Too much boost between 2kHz

and 4kHz can mask certain speech sounds (e.g. ‘m’, ‘b’, ‘v’ can
become indistinguishable). Too much boost anywhere between
1kHz and 4kHz can produce listener fatigue. Vocals can be
highlighted by slightly boosting vocals at 3kHz whilst simultaneously
slightly cutting instruments at that frequency.

5, 6k3, 8k Accentuation & clarity of voice

10, 12k5, 16k Too much boost causes sibilance (’sss’).

Effect of Equalisation on Music Reproduction

1/3 Octave Effect on Music
Centre Frequency

31, 40, 50, 63 Fundamentals of bass drum, tuba, bass and organ. These give music
a sense of power but excessive use can leave the sound ‘muddy’.
Mains Hum (50-60Hz).

80, 100, 125 Too much boost produces ‘boom’. (Fundamentals of tympani & toms)
Higher harmonics of mains hum (100-120Hz)

160, 200, 250 Drum and lower bass. Too much boost produces ‘boom’.
3rd Harmonics of Mains Hum.

315, 400, 500 Fundamentals of strings and percussion.

630, 800, 1k Fundamentals and harmonics of strings, keyboards and percussion.

Boosting 600-1kHz range can make instruments sound horn-like.

1k25 to 4k Drums, guitar, accentuation of vocals, strings and brass.

Excessive boost around 1-2kHz can make instruments sound ‘tinny’.
Excessive boost around 1-4kHz can produce ‘listening fatigue’.

5k, 6k3, 8k Accentuation of percussion, cymbals and snare drum.

Reduction at 5kHz makes overall sound more distant and

transparent.

Reduction of tape hiss and system noise. 1k25 to 8k governs

overall clarity and definition.

10k, 12k5, 16k Cymbals and overall brightness. Too much boost causes sibilance.

Reduction of tape hiss and system noise.

DN370 Operators Manual - Page 12

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 BYPASS

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TRANSFORMER -40dBu +22dBu TRANSFORMER
OPTION OPTION

HIGH PASS LOW PASS NOTCH 1 NOTCH 2 GRAPHIC

PUSH

REMOVE REMOVE
LINK FOR LINK FOR
TX OPTION TX OPTION

PUSH PUSH PUSH PUSH

BYPASS BYPASS BYPASS BYPASS

FREQUENCY FREQUENCY FREQUENCY FREQUENCY

DN370 Operators Manual - Page 13

DN370 (SINGLE CHANNEL) FUNCTIONAL BLOCK DIAGRAM
Functional block diagram
 The DN370 proportional-Q response

The most important design decision for the DN370 was determining the equaliser response. Proportional-Q equalisation, as
used on previous Klark Teknik analogue graphic equalisers, offers some key advantages over the more numerous Symmetrical-Q
equalisers on the market, namely at low amounts of cut or boost the width of the filter is relatively broad and becomes narrower
as the amount of boost or cut is increased, giving a more 'focused' response. This differs from a Symmetrical-Q response which
boosts or cuts an increasingly wide band of frequencies, and is an important consideration in applications such as cutting
particular problem frequencies, as more of the frequency spectrum is scooped out when using Symmetrical-Q equalisation;
proportional-Q equalisers are much better at cutting just the problem frequency band. Symmetrical-Q equalisers are frequently,
but inaccurately, termed Constant-Q as the Q is measured 3 dB up from the point of maximum attenuation when in cut, rather
than the correct definition of 3dB down from the point of maximum gain (0 dB when cutting), which results in a notch filter
response.

In all types of graphic equalisers, one of the key issues is how the summing of adjacent EQ bands alters the frequency response.
Lower-Q filters will blend together more smoothly, but higher-Q filters provide more selective control of problems - at the
expense of more frequency response ripple. A weakness of the Symmetrical-Q approach is that for small amounts of boost and
cut (a very typical situation), the EQ bands have to be comparatively broad to blend smoothly to avoid excessive ripple in the
frequency response, however as the Q of the EQ bands remains constant, larger amounts of boost or cut will affect an
increasingly wide range of frequencies, limiting the precision and usefulness of the equaliser.

Figure 1 and Figure 2 show the responses of a leading Symmetrical-Q equaliser in both its 'wide' and 'narrow' modes of
operation for 2dB of boost and cut, which is typical of the small adjustments made in corrective EQ applications. The 'wide'
response gives a very smooth combined response for the three bands shown, however the 'narrow' response shows significant
ripple in the combined response which will lead to audible artefacts such as phase distortion.

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 1 Symmetrical-Q equaliser “wide” mode ±2dB boost and cut

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 2 Symmetrical-Q equaliser “narrow” mode ±2dB boost and cut

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 The DN370 proportional-Q response

Whilst the 'wide' response is obviously preferable for small amounts of boost and cut, Figure 3 and Figure 4 show the problem
that occurs with using this response for full boost and cut far more of the audio spectrum is affected by each of the bands being
broader as a consequence of maintaining the same Q value.

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 3 Symmetrical-Q equaliser “wide” mode full boost and cut

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 4 Symmetrical-Q equaliser “narrow” mode full boost and cut

The strength of Proportional-Q equalisation is that the EQ bands are wider at lower amounts of boost and cut, and become
narrower as greater amounts are applied, giving the optimum balance of smoothness and accuracy over the entire fader travel.
Extensive listening tests were carried out during the development of the DN370 to obtain the optimum response, resulting in a
very musical sounding equaliser which maintains the highest level of accuracy without ever sounding harsh.

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 The DN370 proportional-Q response

Figure 5 and Figure 6 show the DN370 response for both 2 dB and full scale boost and cut, note that the smooth combining of
the bands for small amounts of boost and cut is very similar to that of the Symmetrical-Q equaliser in its 'wide' mode, whilst as
more boost or cut is applied, the response becomes sharper, giving much more precise control of problem frequencies.

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 5 DN370 response ±2dB boost and cut

+15

+10

+5

d
B +0
u

-5

-10

-15

300 400 500 600 700 800 900 1k 2k 3k 4k

Hz

Figure 6 DN370 response full boost and cut

In addition to the graphic equaliser section, the DN370 also provides sweepable high-pass and low-pass filters and two
overlapping sweepable notch filters per channel. The sweepable high- and low-pass filters can be used to enhance the
intelligibility of wedge monitors by cutting out extraneous low and high frequency noise, and therefore allowing higher SPLs to be
used. The two notch filters further enhance the unit's ability to precisely tune-out problem frequencies. The response of the
notch filters was selected after careful listening to allow feedback to be eliminated quickly, but at the same time to be unobtrusive
when in use. The high-pass, low-pass and notch filter control pots all have push-on, push-off bypass switching, with an
illuminated ring around each pot to show when the filter is active. So for example, if there is particular frequency where a
performer's acoustic guitar causes feedback, one of the notch filters can be used to cut that frequency, and switched out when not
needed whilst still left in position for later in the set when the same instrument may be used again.

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 DN370 applications

Front-of-house
The all-new graphic EQ filters of the DN370 have been carefully selected to allow subtle tonal correction with a minimum of
ripple between adjacent bands. At the same time, the proportional-Q nature of the filters ensures that in the event of acoustic
feedback a tightly-focussed cut response is instantly available just by moving the fader. Range switching between ± 12dB or ±
6dB, together with 45mm long-throw faders provides superb control resolution and excellent visibility of control settings. The
sweepable high and low-pass filters allow the frequency extremes to be matched to the capabilities of the loudspeaker system in
use, leaving all the graphic EQ faders available for acoustic management of the music. Twin sweepable notch filters provide
excellent suppression of room resonances with minimum impact on the program material. Positive in/out switching for all the
filter sections is combined with illuminated rings around the controls for instant “at a glance” status indication.

Monitors
The design of the all-new graphic filters with carefully selected proportional-Q responses ensures that problem frequencies can
be attenuated quickly and effectively. Long-throw faders allow excellent control resolution even when using all of the available
12dB of attenuation. Interaction with adjacent bands is minimised, ensuring that more of the musical content is preserved. Even
more precise are the two sweepable notch filters on each channel, which allow the surgical removal of resonances and feedback
leaving everything else intact. Push switches incorporated in the control knobs allow the filters to be switched easily in and out
(for example when an artist is using different instruments during a show). Illuminated rings around the control knobs ensure that
the filter status is always visible at a glance. High and low pass filters allow the frequency limits to be accurately controlled for
each output. Whilst very useful for conventional wedge monitors, this feature really comes into its own when combining in-ear
and wedge monitors, allowing the response of each monitor subsystem to be tailored to the artist’s requirements.

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 Examples
The additional versatility offered by the
DN370’s unique feature set of filters
allows unparalleled precise control of
frequency response. The examples
adjacent show how the filters can be
used on their own and in conjunction
with the graphic equaliser to handle
problems encountered in real world
corrective EQ applications.

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 DN370 applications

The notch filters on the DN370 can be used to eliminate a common

problem with graphic equalisers - the control of frequencies that lie
+15
between the ISO standard frequency centres. In the adjacent example
to cut 900 Hz, a single notch filter can be used to produce a steep notch +10

in the frequency response without affecting adjacent frequencies (a). In +5

contrast with a Symmetrical-Q equaliser, the only solution available is d
to cut both the 800 Hz and 1 kHz faders, and whilst there is nearly 16 dB B
u
+0
a
of attenuation at 900 Hz, a very broad range of frequencies are also -5
b
affected, particularly when a Symmetrical-Q equaliser with a wide c
-10
response is used (c). A narrow Symmetrical-Q response affects a less
broad range of frequencies, although at the expense of less attenuation -15

at the desired frequency (b). 300Hz 400 500 600 700 800 900 1k 2k 3k 4k

+2
The proportional-Q response of the DN370 simultaneously allows
+0
gentle contouring of the frequency spectrum and precise control of
specific problem frequencies. The sweepable notch filters further -2

enhance this capability. The blue trace shows a high shelf filter created -4
d
using the faders from 2.5 kHz upwards, and a notch created by fully B -6
u
cutting the 800 Hz fader (Channel A on the front panel view). The red -8

trace shows the same shelf filter response, but using a notch filter to cut -10
800 Hz, showing the greater precision offered by the notch filters -12
(Channel B on the front panel view).
-14

200 Hz 500 1k 2k 5k 10k 20k

In contrast, the limitation of Symmetrical-Q equalisers can be seen b

in the adjacent traces - a wide response (a) gives a smooth shelf a
filter but affects a very broad range of frequencies when
attempting to use it as a notch filter, whilst a narrow response (b)
gives a much sharper notch, but at the expense of excessive ripple
in the shelf filter. Even with a narrow response, the Symmetrical-Q
equaliser affects a broader range of frequencies than using the
Proportional-Q response of the DN370’s faders.

The ability to overlap the notch filters, both with each other and with the a
graphic EQ bands, allows very deep notches to be created. The adjacent
trace shows the responses of a single notch filter, two overlapped notch
filters (a) and two notch filters overlapped with an EQ band (b), each b
resulting in greater attenuation (c). Nearly 45 dB of attenuation is
possible when using the notch filters in conjunction with the EQ bands.
c

A typical application of DN370 would be to EQ a monitor wedge, the red

trace shows how both the high and low pass filters have been used to
+0
shape the overall response, and the use of the two notch filters to
attenuate particular problem frequencies. Note that the faders are -5

completely flat, and so can be used to make incremental changes -10

relative to the response shown above. In contrast, a Symmetrical-Q -15 a

d
equaliser even with a high pass filter cannot produce the same B
-20
b
u
response, either with a wide or narrow response (b and a traces). The
-25
effect of the interaction caused by combining the individual fader
-30
responses makes it impossible to match the response created using the
DN370’s filters, and whilst the narrow response is more able to produce -35

the desired notches, it is again at the expense of ripple in the low pass -40
10 Hz 20 50 100 200 500 1k 2k 5k 10k 20k
filter response.
+0
a
-5
b
-10
A Symmetrical-Q equaliser lacking the additional filters cannot produce
a high pass filter response using just its faders, either with a wide or d
-15

B
narrow response (b and a traces). The user may assume that subsonic u -20

frequencies are being attenuated by cutting the bottom faders but the -25

graph shows that this is not the case. -30

-35

-40
10 Hz 20 50 100 200 500 1k 2k 5k 10k 20k

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 DN370 Operators Manual - Page 20

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 Technical specification

Inputs Two
Type Electronically balanced (pin 2 hot)
Impedance (Ohm) 20k
Max input level +22dBu

Outputs Two
Type Electronically balanced (pin 2 hot)
Minimum load impedance 600ohms
Source impedance <60ohms
Maximum output level +22dBu >2k ohm

Performance
Frequency response
EQ out ±0.5dBu, 20Hz-20kHz relative to signal at 1kHz
EQ in (flat) ±0.5dBu
Distortion (THD+N) < 0.003% @ 1kHz, +4dBu
l a r k te k n i k .c o m
Dynamic range >114dB (20Hz-20kHz unweighted), ±12dB range
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
Audio 3-pin XLR and 6-pin Phoenix
Power 3-pin IEC

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 5.8kg
Shipping 7.0kg

Options Input and output balancing transformer

BS EN ISO 266:1997 Frequency Centres:

The ISO standard frequencies

25 Hz, 31.5 Hz, 40 Hz, 50 Hz, 63 Hz, 80 Hz, 100 Hz, 125 Hz, 160 Hz, 200Hz, 250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 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 Hz

Due to a policy of continual improvement, the Klark Teknik Group reserves the right to alter the function or specification at any time without notice.

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 Frequency chart

+6 +12

-6 -12

# b # # # b # # b
C E F G B
b
C E F G B

C D E F G A B C D E F G A B C

PIANO
LARGE PIPE ORGAN

VIOLIN
VIOLA
CELLO
DOUBLE BASS

PICCOLO
FLUTE
OBOE
BASSOON

TRUMPET
TROMBONE
TUBA

SOPRANO
CONTRALTO
BARITONE
BASS

BASS DRUM SNARE & TOMS

DRUM KIT (BASS DRUM/SNARE+TOMS)
GUITAR

DN370 HIGH PASS FILTER DN370 LOW PASS FILTER

DN370 NOTCH FILTER RANGE

DN370 NOTCH FILTER RANGE

PEJ MMIV

Note: The above information is provided as a rough guide to the range of fundamental frequencies used by various common
instruments. In addition to these, various amounts of higher harmonic content will also be produced.
A=440Hz

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 +6 +12

-6 -12

+6 +12
DN370 DUAL GRAPHIC EQUALISER

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-6 -12

Location

Application Date
DN370 DUAL GRAPHIC EQUALISER

+6 +12

DN370 Operators Manual - Page 23

-6 -12

+6 +12
DN370 DUAL GRAPHIC EQUALISER

-6 -12

Location

Application Date
DN370 DUAL GRAPHIC EQUALISER
Crib sheet
 Klark Teknik DN370 Operators Manual
Issue 1 - February 2004
DOC02-DN370
(c) Klark Teknik Group (UK) PLC.

In line with the company’s policy of continual improvement, specifications and function may be subject to
change without notice. The contents of this Operators Manual was correct at the time of writing. E&OE.

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