Klein + Hummel O 300 User manual

Operating Manual
O 300
O 300 D
Part Number: 520542
Version: 02
Date: 29-May-2009
Language: English
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Klein + Hummel
O 300 (D) Operating Manual 1
Introduction
Thank-you for purchasing a Klein + Hummel loudspeaker. A Mathematically Modeled Dispersion™ waveguide
(MMD™), flexible acoustical controls, various input options and an extensive mounting hardware range allow the
loudspeaker to be used in diverse acoustical conditions, with any source equipment and in a wide variety of
physical locations. The latest acoustical and electrical techniques and components have been used to ensure the
most accurate sound reproduction possible. Klein + Hummel products are designed for longevity so we hope you
enjoy many happy years of using this product.
Depending on the size, Klein + Hummel’s three-way systems are designed for use as near field monitors through
to large main control room monitors. They can be used in music, broadcast, and post production studios for
tracking, mixing, and mastering. They may be positioned free-standing or flush mounted into a wall, and can be
mixed freely in multichannel systems.
Before reading the rest of this operating manual, review the safety and warnings section towards the back of this
book. Note that imperial dimensions are approximate.
Package Contents
The shipping carton contains:
•This operating manual
•Product guarantee
•The loudspeaker
•A mains power cable (Euro or USA)
Signal cables are not included. Options and accessories are listed at the end of this operating manual.
Most Common Applications and Listening Distances
The minimum, recommended, and maximum listening distances are shown below, together with their most
common application:
Distances
Product Most Common Application Minimum Recommended Maximum
O 300 (D) Near-field monitoring 0.75 m (2.5’) 1.0 – 2.5 m (3’ - 8‘) 6 m (18’)
In multichannel systems, one should ideally use the same product for all main channels. However, as the rear
channels often contain less bass and the signals are mixed at a lower level than the front channels, the rear
loudspeakers can be smaller - table below for details. The center loudspeaker should always be of the same type
as the left and right loudspeaker. The subwoofer should be sufficient to keep up with the main loudspeakers
- see subwoofer operating manual for details.
Front Ideal Rears Smaller Rears Subwoofer(s)
O 410 O 410 O 300 (D) Refer to subwoofer operating manuals
O 300 (D) O 300 (D) O 110 (D), M52 (D) Refer to subwoofer operating manuals
Please refer to the Product Selection Guide for more information about building systems using K+H products.

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O 300 (D) Operating Manual 2
System Block Diagrams
O 300 Block Diagram
O 300 D Block Diagram
Refer to the detailed product specifications section for information on the crossover frequencies, amplifier power,
and driver types. When the Pro C 28 external controller is used on an O 300 D, all internal limiters are bypassed,
except the bass channel peak limiter.

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O 300 (D) Operating Manual 3
Electronics Panel Picture
O 300 electronics panel
O 300 D electronics panel

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O 300 (D) Operating Manual 4
Analog Input Stage
The O 300 input stage is a 14 k Ωelectronically balanced type on a female XLR socket.
The O 300 D input stage is a 14 k Ωtransformer balanced type on a female XLR socket.
Pin Signal
1 Audio Ground
2 Positive
3 Negative
Analog connections on the O 300 and O 300 D
If there is a humming or buzzing sound coming from the loudspeaker, first check it is not the loudspeaker by
disconnection the input signal cables. If the noise goes away it is not the loudspeaker itself and so the noises
must be coming from the cabling or the source. There are various ways to increase the loudspeaker’s immunity
from these external noises:
•Use the ground lift switch to disconnect the audio ground from the electronics’ chassis ground. For safety
reasons, the electronics chassis ground is always connected to the mains power earth pin.
•Use an O 300 D which is fitted with a transformer balanced input stage. This is especially effective when
combined with the ground lift switch.
•If unbalanced cables are used, they can be specially wired – see picture below. Disconnect the cable screen
from the RCA sleeve if there are still humming or buzzing sounds, and/or use the ground lift switch on the
loudspeaker.
Source (RCA) Loudspeaker
(XLR-M)
1
3
2
Unbalanced RCA to Balanced XLR Connections
Cable for connecting unbalanced sources to a balanced XLR input
Digital Input Stage (O 300 D only)
In the O 300D there is a 16…24-bit, 32…96 kHz digital input stage that can accept AES3-2003 (commonly known
as AES/EBU), AES3id-2001, and S/P-DIF (with a suitable connector converter) signals. De-emphasis is supported
on 32, 44.1, 48, and 96 kHz sample rates. XLR and BNC connectors ensure good interconnectivity options.

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O 300 (D) Operating Manual 5
Uncompressed PCM AES3, AES3id, and S/P-DIF digital signals generally contain two audio channels (called
“subframe A” and “subframe B”) on one cable (single-wire mode). A clock input is not required because
loudspeakers are not audio sources and the clock signal is locally regenerated from data contained in the bit
stream. The four-way signal selector switch on the rear panel allows selection of:
•“ANALOG” (XLR input connector only).
•“R” (digital subframe B)
•“L” (digital subframe A)
•“MONO” (mono sum of subframe A and subframe B with a 4.5 dB attenuation)
There is no digital output from the BNC connector when the XLR input is presented with an analog signal,
therefore the O 300D cannot be used as an analogue-to-digital converter.
Always use good quality cables with the correct impedance and appropriate termination to achieve these
maximum cable lengths:
Format
(Connector)
Impedance Cable Length
S/P-DIF (RCA) 75 Ωup to 10 m (30’)
AES3 (XLR) 110 Ωup to 100 m (300’)
AES3id (BNC) 75 Ωup to 1000 m (3000’)
An AES3 signal (applied to the XLR connector) is point-to-point and may not be looped, so the BNC connector is
used to connect additional monitors to the AES3 signal. The signal selector switch on the first loudspeaker should
be set to the “L”, “R”, or “MONO” setting. This outputs an AES3id signal from the BNC connector for connecting
additional monitors to the original AES3 signal. The BNC connector is not internally terminated so a single 75 Ω
termination is required at the end of the BNC transmission line. This can be realized using T-piece and a 75 Ω
terminator (not supplied).
XLR digital input connections on the O 300 D
An AES3id or S/P-DIF signal (applied to the BNC connector) can be looped using a T-piece connector (not
supplied) for connecting additional monitors to the input signal. The signal selector switch on the first
loudspeaker should be set to “L”, “R”, or “MONO” setting. An appropriate setting should be made on the rear
panel signal selector switch depending on the signal channel order and loudspeaker position. See picture below:

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O 300 (D) Operating Manual 6
AES3id or S/P-DIF
Digital Source
Subframe A – Left signal
Subframe B – Right signal
BNC BNC
Set rear panel
switch to “LEFT”
Set rear panel
switch to “RIGHT”
75 Ω
Terminator
T-piece
BNC digital input connections on the O 300 D
To connect multiple O 300 D monitors together, use BNC T-piece connectors (not supplied) - see picture below. in
The digital input can be applied to either the XLR or BNC input of the first loudspeaker in the chain. BNC
connectors should be used for the rest of the loudspeakers in the chain. An appropriate setting should be made
on the rear panel signal selector switch depending on the location of the loudspeaker.
Multiple O 300 D connections using BNC
Note that the BNC connector has no output driver. When using the AES3 input, the output level is derived
passively from the AES3 signal’s input level. This has a wide tolerance, therefore the length of the
interconnection cable and number of loudspeakers will depend on the level of the source signal and quality of the
interconnecting cables.
It is not possible to have an analog XLR and a digital BNC cable simultaneously connected to the loudspeaker as
the BNC connector is parallel connected to the XLR input.
Acoustical Controls
Klein + Hummel loudspeakers are designed to have a flat pass band magnitude response in anechoic conditions
when all the acoustical controls are set to 0 dB. When a loudspeaker is installed into a listening environment the
response changes and thus should be corrected back to a flat response. It is therefore expected that the controls
will need adjustment to improve the in-situ response of the loudspeaker. The acoustical controls’ settings will
depend on the loudspeaker’s location and will probably be different for the same loudspeaker type installed in
different locations in the same room. In a symmetrical installation, left/right pairs (front or back) will probably
have the same acoustical settings. Suggested settings are shown after this description of the controls:
The bass control is used to compensate for the effect of loading due to nearby large solid boundaries such as
walls. Four settings are available: 0, -3, -6, and -9 dB.

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O 300 (D) Operating Manual 7
The mid control is used to compensate for the acoustical loading experienced when the loudspeaker cabinet is
placed near a large reflecting surface, such as a mixing console. Four settings are available: +2, 0, -2, and -4 dB.
The treble control affects the treble driver output level and can be used to compensate for insufficient or
excessive high frequency damping in the room. The treble control is often set to suit the listener’s taste, although
in well-controlled environments there should be little reason to adjust it away from 0 dB. Four settings are
available: +2, +1, 0, and -1 dB.
It is advised that an acoustical measurement system be used to set these controls in the most appropriate way
for the loudspeaker’s location. In the absence of appropriate equipment the following settings are recommended
as a good starting point for further adjustment:
Acoustical Controls
Loudspeaker Location
Bass Mid Treble
In a corner -9 dB -2 dB -
Next to or flush mounted in a solid wall -6 dB - -
Next to or flush mounted in a soft wall -3 dB - -
Free standing in an untreated room -3 dB -2 dB -1 dB
Free standing in a well-treated room - - -
In small room with strong side-wall reflections1- +2 dB -
Near a desktop or an a meter bridge1- -2 dB -
1.Setting should be used in addition to the one of the top five settings.
O 300 (D) Acoustical Controls
The input attenuator control allows the loudspeaker to be matched to a wide range of equipment outputs whilst
maintaining the desired acoustical output. In the O 300 D, the attenuator affects the output level as it is
positioned after the DAC. As with any other component in the audio chain, it is best to use the lowest gain for the
application so as to minimize amplification of the preceding equipment’s source noise. To check this, if the noise
drops dramatically when the input cable is unplugged, the noise is coming from the source not the loudspeaker.
The default setting is “0 dB”, and this gives an output level of 96 dB SPL at 1 m when the input signal is
0 dBu (0.775 V), which is the same as 100 dB SPL at 1 m when the input signal is +4 dBu (1.23 V). Below are
some examples of how to calculate the output level:
Input signal [dBu] 0 (0.775 V) 0 (0.775 V) +4 (1.23 V) -20 (77.5 mV)
Input attenuator setting [dB] 0 -24 0 0
Loudspeaker output for 0 dBu input [dB SPL] 96 96 96 96
Sound output of loudspeaker [dB SPL at 1m] 96 72 100 76
In Europe 0 dBu is -18 dBFS (EBU standard R68). In the US +4 dBu is -20 dBFS (SMPTE standard RP155). These
dBu values should equate to 85 dB SPL at the listening position. It is typical in the broadcast industry to use a
reference level of 79 dB SPL at the listening position. Near field loudspeakers can be as close as 1 m from the
listening position, whereas loudspeakers in a Dolby certified movie mixing room should be at least 5 m from the
listening position. In the examples below, it is assumed that the listener is inside the room radius and thus the
sound field decays according to 20 log10 (r), however this may not always be the case.

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O 300 (D) Operating Manual 8
Input signal [dBu] 0 (0.775 V) +4 (1.23 V)
Loudspeaker output for 0 dBu input [dB SPL] 96 96
Input gain [dB] -5 -9
Listening distance [m] (dB change) 2 m (-6 dB) 2 m (-6 dB)
Loudspeaker output level [dB SPL] 85 85
The maximum level that the O 300 electronic balanced input stage can accept is +20 dBu (7.75 V). The maximum
level that the O 300 D transformer balanced input stage can accept is +24 dBu (12.3 V). To avoid clipping the
input stage, decrease the amount of input attenuation. The maximum acoustical output of the loudspeaker is
limited by the protection system. In general, larger loudspeakers can play louder and for longer periods than
smaller loudspeakers.
Other Controls
The power On/Off switch turns the mains power completely on and off. The applied mains power voltage should
be within -15% and +10% of the value shown on the electronics panel. The mains fuse value depends on the
mains voltage and should be:
Mains Voltage Fuse (250 V)
220 - 240 V T 1.6
120 V T 3.15
100 V T 4
Crossover
Using 4th order filters, the crossover divides the input signal into three bands for reproduction by the appropriate
sized driver. Time alignment of drivers is accomplished with the physical position of the drivers on the front
panel, therefore electronic alignment is necessary. In addition to this an extensive protection system ensures that
the loudspeaker is not damaged if a large signal is applied to the input. The front panel K+H logo flashes when
the protection system is active. If this happens, reduce the input signal. If this happens regularly, use a larger
loudspeaker with a higher SPL output, or add a subwoofer to handle the high-level low-frequency energy. The
protection system consists of: thermal and peak limiters for the amplifiers, thermal modeling of the drivers, and
an excursion limiter for the drivers.
The protection system is not a compressor, it is designed to protect the loudspeaker from damage, and the
flashing K+H logo tells the user it is active. The protection cannot protect against sustained abuse of the
loudspeaker, i.e. consistently playing the loudspeaker for long periods of time with the protect light on, so avoid
this to ensure a long life from this product.
There are also production trimmers in the crossover section which are hidden from view to avoid “accidental”
adjustment. These should only be adjusted by qualified personnel with specialized measurement equipment. If a
component critical for sound quality, e.g. bass driver, is changed, the loudspeaker should ideally be recalibrated in
a Klein + Hummel Continental Service Center, i.e. one equipped with an anechoic chamber.
Amplifiers
Monolithic integrated circuit class AB amplifiers are used because, for full range loudspeakers, the overall
performance is still better than any other solution. Harmonic and intermodulation distortions, and noise are all
consistently low in well-designed class AB amplifiers. Some space (5 cm, 2”) is required around the electronics
panel.
It is recommended that the amplifier heatsink is checked for any build-up of dust and fluff at least every six
months. The heatsinks can be cleaned by blowing clean compressed air across the external heatsink. Failure to do
this may limit maximum SPL output.
As the electronics back panel seals the enclosure, it cannot be remote mounted. If the cabinet is to be flush
mounted, care should be taken to ensure that there is adequate ventilation. Although no damage will result,
insufficient cooling will cause the amplifier protection to activate prematurely thereby limiting the system’s
maximum output level.

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O 300 (D) Operating Manual 9
On the O 300 D there is the facility to connect a Pro C 28 using the power amplifier direct input. This adds the
possibility to compensate the response for amplitude and phase anomalies resulting from the monitor’s
placement in the room or the acoustic conditions of the room. In addition, a 10 band parametric equalizer and up
to 1 second delay allow the monitor to be tuned in ways not possible using the built-in analog acoustical controls.
Drivers
The drivers are the best available for their application. Long throw, efficient, low distortion drivers ensure a clean
sound quality even at high replay levels. The bass driver is loaded by the internal volume of the cabinet. The mid
and treble drivers have their own self-contained back cavities. All drivers are magnetically shielded for use next
to CRT screens and magnetic storage media. The system’s SPL output and the cabinet volume can be seen in the
specifications section below.
Waveguide
The midrange and treble drivers are mounted into a waveguide. The entire front panel is constructed using Low
Resonance Integral Molding materials (LRIM™). It was computer simulated and then experimentally verified in an
anechoic chamber to give optimum control of the directivity of the midrange and treble drivers. The benefits are
increased driver loading, reduced edge diffraction and room reflections, a smoother power response, and a wide
useable listening area. The result is a reduced audio distortion and a corresponding sound quality improvement.
The waveguide has 90° x 60° dispersion and so it is generally recommended to mount the loudspeaker cabinet
horizontally. An exception to this general rule is, for example, in OB vans where the listening position is fixed and
strong side wall reflections need to be suppressed.
In all cabinet orientations, the acoustical axis should point towards the engineer’s listening position, or the center
of the listening area, in both the horizontal and vertical planes – see Cabinet section for a definition of the
acoustical axis.
Cabinet
The wooden cabinet is painted using a standard RAL color. An appropriately colored pen can be used to touch up
the paintwork if it is scratched during transport or use. The following RAL numbers correspond to K+H standard
cabinet colors.
K+H Color Name RAL Number
Anthracite 7021
Silver 9006
User specified RAL colors may be specified, however there are some conditions attached to this. Contact the local
distributor for details.
The acoustical axis is a line normal to the loudspeaker’s front panel along which the microphone was placed when
tuning the loudspeaker’s crossover during design. Pointing the acoustical axis, in the horizontal and vertical
planes, towards the listening position or centre of the listening area will give the best measured and perceived
sound quality. For three-way loudspeakers in the Klein + Hummel range, the acoustical axis is located on the mid-
point of the midrange and tweeter drivers.
Product x dimension y dimension
O 300 30.5 cm (12“) 14.5 cm (5 3/4“)
O 300 D 30.5 cm (12“) 14.5 cm (5 3/4“)

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O 300 (D) Operating Manual 10
x
y
O 300 (D) Acoustical Axis
An M8 thread is positioned on either side of the cabinet for attaching an LH 25 “U” bracket. The plastic plugs
should be refitted if the LH 25 is later removed.
Angled metal brackets on the rear panel can be used to mount the cabinet on a wall or as handles to lift the
loudspeaker. Note: Do not place the O 300 (D) face down on a flat surface as the midrange driver will be
damaged.
System Use
Klein + Hummel loudspeakers should only be used indoors and in these ambient conditions:
•+10° C to +40° C (+50° F to +104° F), <90% relative humidity, non-condensing
During transport or storage the ambient conditions can be:
•-25° C to +70° C (-13° F to 158° F), <90% relative humidity, non-condensing
Before connecting the mains power cable, ensure that the correct mains voltage is indicated on the electronics
panel (230, 120, or 100 V) and that the mains power switch is off. Next connect the input signal cable (analog,
digital, or both as appropriate) and power up the loudspeaker. There will be a five second delay before sound can
be heard from the loudspeaker so as to avoid noises (pops) from preceding equipment turned on at the same
time. Conversely, turning off the loudspeaker immediately mutes the audio. The K+H logo should light up. If there
are no lights, check the mains power supply.
In a studio application, the loudspeakers should be placed according to the ITU-R BS.775-1 recommendations so
there is consistency of reproduction when compared to other listening environments. For movie applications,
ANSI/SMPTE 202M is the preferred standard for system setup. For home use, as materials are mixed in ITU style
rooms, one should get as close as possible to this configuration to maximize replay authenticity.
For two-channel stereo, ±30° should be used. There are currently no internationally agreed standards for 6.1 or
7.1 formats. However common practice is to use one or two loudspeakers in the centre back location of a 6.1
system. In a 7.1 system common practice is to place side loudspeakers at ±90° and to push the surround
loudspeakers back to ±150°.
For the best stereo imaging the loudspeakers should be placed symmetrical, in a symmetrical room, where
objects have been placed symmetrically. This ensures the same response from each loudspeaker at the listening
position and thus good imaging. Sound reflected back to the listening position should also be minimized using
surface angling or acoustical treatment. The acoustical axis should point towards the listening position or centre
of the listening area in both the horizontal and vertical planes.
Loudspeaker Name ITU-R BS.775-1 Angle ANSI/SMPTE 202M Angle
Left -30° -22.5°
Center 0° 0°
Right 30° 22.5°
Left Surround -110°±10° An array to the left
Right Surround 110°±10° An array to the right

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O 300 (D) Operating Manual 11
The O 300 (D) comes in two forms: named “left” and “right”. In a two-channel system, one of each type is used
and the bass drivers, normally, positioned on the inside. In a multichannel system, “left”/”right” pairs can be
used for rears and sides. For the center, either a “left” or “right” may be used, with the acoustical axis lined up
along the centre line of the loudspeaker array – see picture below. Ideally, all front loudspeakers are positioned at
the same height.
↑↑↑
-30 deg 0 deg +30 deg
Using the O 300 (D) as a center loudspeaker
The loudspeaker should be placed on a circle to ensure equal time of arrival of the audio from all loudspeakers.
Failing this, appropriate electronic time delays should be added to compensate for time of flight differences. This
can either be a Pro C 28 inserted into the signal chain before an O 300 or a Pro C 28 attached to the power
amplifier direct input on an O 300 D.
If the loudspeaker is used free standing, good quality loudspeaker stands and suitable accessories (see
Accessories and Options section) are recommended.
The benefits of flush mounting are reduced cabinet edge diffraction (smoother midrange), increased bass driver
loading (reduced bass distortion), and elimination of rear wall cancellations (smoother bass response). It is a
good idea to employ an experienced acoustic engineer to design an effective flush mounting wall. Recommended
acoustical control settings are shown in the Acoustical Controls section. If the loudspeaker must be covered, use a
thin open weave cloth. Two layers of very thin material will improve opacity.
Before trimming the levels, calibrate each loudspeaker’s response:
•In studio applications, the response of each loudspeaker at the listening position should be flat.
•In movie applications, the response of each loudspeaker should be one of the X-curve shapes, depending on
the size of the room (see ANSI/SMPTE 202M).
•In home applications, the response of each loudspeaker should be set for subjective audio quality. This is not
necessarily a flat response, but generally, with time, a gently downward sloping response with increasing
frequency is often preferred.
Absolute acoustic level calibration is achieved using a sound level meter set to ‘C’-weighting and a “slow”
integration time. Play a broadband pink noise test signal set to -18 dBFS (Europe) or -20 dBFS (USA) on the
console meters and measure the sound pressure level at the listening position. Then adjust each channel’s level
(can also be adjusted on all loudspeakers for a specific channel) until the desired level is achieved:
Application SPL
Movie 85 dB(C)
Broadcast 79 dB(C)
Music Engineer’s preference
For information on setting up a subwoofer with these main loudspeakers, please refer to the operating manual
supplied with the subwoofer.

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O 300 (D) Operating Manual 12
Technical Specifications
O 300 O 300 D
Acoustics
-3 dB free field frequency response 35 Hz … 24 kHz, ± 3 dB 35 Hz … 24 kHz, ± 3 dB
Pass band free field frequency response 40 Hz … 20 kHz, ± 2 dB 40 Hz … 20 kHz, ± 2 dB
Self-generated noise <20 dB(A) at 10 cm <20 dB(A) at 10 cm
Sine wave output with a THD < 0.5 % at 1 m 95 dB SPL (>100 Hz) 95 dB SPL (>100 Hz)
Max. SPL In half space at 3% THD 112.8 dB SPL 112.8 dB SPL
Averaged between 100 Hz and 6 kHz 100 Hz and 6 kHz
Electronics
Woofer amplifier, cont.(peak) output power* 150 W (250 W) 150 W (250 W)
Mid amplifier, cont. (peak) output power* 65 W (75 W) 65 W (75 W)
Tweeter amplifier, cont.(peak) output power* 65 W (110 W) 65 W (110 W)
Controller design analog, active Internal active analog, or
external DSP (K+H Pro C 28)
Crossover Frequency 650 Hz/3.3 kHz 650 Hz/3.3 kHz
Crossover Slope (dB/oct.) 24 24
Equalization: Low cut – –
Bass 0, -3, -6, -9 dB 0, -3, -6, -9 dB
Mid +2, 0, -2, -4 dB +2, 0, -2, -4 dB
High +1, +2, 0, -1 dB +1, +2, 0, -1 dB
Time of Flight adjustment delay – 8 … 1000 ms using a Pro C 28
Protection circuitry Limiter: low, mid, high Limiter: low, mid, high
Infrasonic filter frequency; slope 30 Hz; 6 dB/oct. 30 Hz; 6 dB/oct.
Analog Input
Impedance, electrically balanced XLR, 14 k Ω-
Impedance, transformer balanced - XLR, 14 k Ω
Input sensitivity +6 dBu +6 dBu
Gain control 0 … -24 dB 0 … -24 dB
CMRR >60 dB @ 15 kHz >60 dB @ 15 kHz
Digital Input/Output
Format XLR (Format BNC) - AES3 (AES3id, S/P-DIF)
Impedance XLR, balanced - 110 Ω
Impedance BNC, unbalanced - 75 Ω(input/output)
Input switching - Analog / Digital L, R, Mono
Digital converter: resolution, design - 16 … 24-bit DAC, ΔΣ
sampling rate - 32 … 96 kHz
Digital sensitivity - -12.5 dBFS
D-A dynamic range - 120 dB
Displays and Mains Power
Displays and indicators: power on K + H logo “Red” K + H logo “Red”
limit/clip K + H logo “Flashing” K + H logo “Flashing”
Mains power 230, 120, or 100 V AC 230, 120, or 100 V AC
Power consumption - Idle 18 VA 19 VA
Power consumption - Full output AC 240 VA 241 VA
Mechanics
Height x width x depth, mm 253 x 383 x 290 mm 253 x 383 x 290 mm
inches 10” x 15 1/8” x 11 3/8” 10” x 15 1/8” x 11 3/8”
Internal net volume 18.3 liters 18.3 liters
External volume 28 liters 28 liters
Weight 13.4 kg (29.5 lbs) 13.4 kg (29.5lbs)
Drivers Magnetically shielded Magnetically shielded
Woofer 210 mm (8") 210 mm (8")
Midrange 76 mm (3") 76 mm (3")
Tweeter 25 mm (1") 25 mm (1")
Mounting points 2 x M8 on sides 2 x M8 on sides
Mounting hardware included Rear panel bracket Rear panel bracket
Cabinet surface finish Painted Painted
Color: standard Anthracite (RAL 7021) or
silver (RAL 9006)
Anthracite (RAL 7021) or
silver (RAL 9006)
Color: custom User specified RAL User specified RAL
Baffle cover Optional metal grille Optional metal grille
*THD+N < 0.1 % with limiter deactivated

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O 300 (D) Operating Manual 13
Acoustical Measurements
Below are acoustical measurements conducted in anechoic conditions at 1 m. Color versions of these graphs can
be found on the appropriate product page of the klein-hummel.com web site.
O 300 (D) free-field response O 300 (D) group delay
O 300 (D) horizontal directivity plot O 300 (D) vertical directivity plot
O 300 (D) distortion at 95 dB SPL O 300 (D) Maximum SPL at 1 m (3% and 1%)
(Yellow: THD, Red: 2
nd
harmonic, Green: 3
rd
harmonic)
O 300 (D) cumulative spectral decay

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O 300 (D) Operating Manual 14
Accessories and Options
In this section is a description of the options and accessories that are available for the products covered in the
operating manual. Note that options and accessories are fitted at the user’s own risk and that safety and
warning instructions should be observed.
Mounting hardware
A collection of hardware for mounting the loudspeaker (available in black only, unless otherwise stated):
LH 25 (W) “U” bracket – Bracket to aid mounting on ceilings, walls, or loudspeaker stands. Allows for ±20°of
vertical adjustment. Available in black or white.
LH 28 (W) Tripod stand adapter – Adapter for mounting onto a 35mm tripod stand, black or white
LH 29 TV spigot adapter – Adaptor for mounting onto a lighting tripods stand or truss bar, silver.
LH 33 Tilt connector – Adaptor to give 0-15°angling on loudspeaker stands.
LH 36 Tilting adapter – Tilting adapter for a loudspeaker mounted on a subwoofer or loudspeaker stand.
LH 37 Tripod flange adapter – Adapter for 35mm flanges.
LH 41 Base plate – Used to fit the loudspeaker onto a tripod stand. Adding an LH 36 gives a tilting
function.
LH 43 Ceiling mounting plate – Used to mount the loudspeaker flush onto a ceiling.
LH 45 Wall mount ‘L’ bracket – 'L' shaped adapter to mount the loudspeaker onto a wall.
LH 46 Adjustable ceiling drop adapter – Mounting hardware to vertically position a loudspeaker
suspended off a ceiling.
LH 47 Mounting adaptor plate 115 mm – Tripod adaptor plate to mount the LH 25 onto an LH 43, LH 45,
or LH 46.
LH 48 Tripod adaptor plate 115 mm – Tripod adaptor plate to mount on to König & Meyer tripods No.
26790 and No. 26795.
C 15 Eyebolt – Safety connection with M8 thread, silver.
LH 25 (W) – “U” bracket LH 28 (W) – Tripod stand adapter
LH 29 – TV spigot adapter LH 33 – Tilt connector
LH 36 – Tilting adapter LH 37 – Tripod flange adapter

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O 300 (D) Operating Manual 15
LH 41 – Base plate LH 43 – Ceiling mounting plate
LH 45 – Wall mount ‘L’ bracket LH 46 – Adjustable Ceiling Drop Adapter
LH 47 – Mounting Adaptor Plate 115 mm LH 48 – Tripod Adaptor Plate 115 mm
C 15 – Eyebolt
Suitable combinations of the above hardware are:
Location of Loudspeaker Hardware Combinations
On a Loudspeaker Stand LH 25 + LH 28
LH 41 + LH 28
LH 25 + LH 48 + K&M26790
LH 25 + LH 48 + K&M26795
LH 41 + K&M26790
LH 41 + K&M26795
On a Lighting Stand LH 25 + LH 29
LH 41 + LH 29
On a Subwoofer
(fitted with a flange)
LH 25 + LH 37
LH 41 + LH 37
LH 25 + LH 28 + pole
LH 41 + LH 28 + pole
On a Wall LH 25
LH 25 + LH 47 + LH 45
Included rear panel brackets
Off a Ceiling LH 25
LH 25 + LH 47 + LH 43
LH 25 + LH 47 + LH 46
Off a Lighting or Truss Bar LH 42 + LH 29
Safety Connection C 15
Detailed mechanical drawings of these accessories can be found on line at www.klein-hummel.com.

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O 300 (D) Operating Manual 16
Controller multicore cable (CMK 5)
A cable used to connect a Pro C 28 to the O 300 D (pictured below).
Metal grille (GO 300)
A metal grille can be attached to the front of the loudspeaker to protect the drivers. It simply clips into the
grooves on the long sides of the cabinet and adds 22 mm (7/8”) to the depth and 3 mm (1/8”) to the height of
the cabinet. It is damped to avoid rattles and has been designed for acoustic transparency (black version pictured
below). The grille is available in black and silver.
Flight case (FO 300)
As the original packing is primarily designed to get the loudspeaker from the factory to the end user, it is highly
recommended that a flight case is used if the loudspeaker is regularly moved between locations. One O 300 (D)
can be packed in the flight case.
CMK
5 – Multicore cable GO 300 – Metal Grille
EC Declaration of Conformity
This equipment is in compliance with the essential requirements and other relevant provisions of Directives
89/336/EC and 73/23/EC. The declaration is available on the internet site at www.klein-hummel.com. Before
putting the device into operation, please observe any respective country-specific regulations.
For loudspeakers fitted with digital inputs: Compliance to FCC Rules
This device complies with part 15 of the FCC Rules and with RSS-210 of Industry Canada. Operation is subject to
the following two conditions:
•This device may not cause harmful interference, and
•This device must accept any interference received, including interference that may cause undesired operation.
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part
15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a
residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a particular installation. If this equipment does
cause harmful interference to radio or television reception, which can be determined by turning the equipment
off and on, the user is encouraged to try to correct the interference by one or more of the following measures:
•Reorient or relocate the receiving antenna.
•Increase the separation between the equipment and receiver.
•Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
•Consult the dealer or an experienced radio/TV technician for help.
This class B digital apparatus complies with the Canadian ICES-003
Changes or modifications to this equipment not expressly approved by Klein + Hummel may void the FCC
authorization to operate this equipment.

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O 300 (D) Operating Manual 17
Safety and Warnings
In addition to specific warnings throughout this document, please observe these additional general instructions.
The term “loudspeaker” includes the case when the electronics of an active loudspeaker is installed into a Remote
Electronics Kit, or when it is still located in the back of the cabinet.
This symbol means that a high voltage is to found nearby. Take appropriate precautions to avoid
electric shocks.
This symbol means that hot parts of the product may be found nearby. Take appropriate precautions
to avoid burns.
General
•Keep these instructions in a safe place for future reference.
•Failure to follow the safety and warning instructions contained in this document voids the warranty.
•This product should be used for the intention for which it was designed and as described in this document.
Environment
•Ensure that the room in which you use this product is wired in accordance with the local electrical code and
checked by a qualified inspector.
•A correctly earthed mains power connection should always be used.
•If access to the interior electronics is required, disconnect it from the mains power and allow electrical energy
storage devices, such as capacitors and transformers, to discharge.
•Other electronic products may generate sufficient heat to require ventilation.
•Do not block or cover heatsinks, fans, or vents.
•Unless otherwise stated, this product is designed to be used indoors only.
•Do not expose this product to water, any other liquids, moisture, or naked flames.
•Do not install this product into hot, humid, or excessively dusty locations, or into direct sunlight.
•Avoid installing this product into locations where it will experience externally generated vibrations or heat
(e.g. radiators).
•If the product is moved from a cold environment into a warm one (such as from a vehicle into a building), it is
possible that condensation will form. Please allow the product sufficient time for acclimatization to room
temperature before using.
•Wherever an amplifier is located, a free flow of air should be maintained by leaving a gap of at least
5 cm (2”) around it. A flush mounted cabinet with the electronics panel still installed should be
well-ventilated to avoid heat build-up and possible risk of fire.
Use
•The equipment should be mounted by a suitably qualified professional in accordance with local, national, and
international regulations and standards.
•Falling equipment can damage itself, people, and other objects, so do not place this unit on any unstable
platform, cart, trolley, stand, table, or mounting hardware.
•Do not use accessories and options with this product that are not approved by Klein + Hummel.
•Mounting hardware must be attached to the appropriate hardware and attachment points rated and
intended for such use.
•Ensure that the operating voltage of this product matches that of the local mains voltage.
•Use the power cable that came with this product as this has been manufactured to international safety
standards. If it has been damaged obtain a similarly certified and specified mains power cable.
•This product should be unplugged from the mains power and the signal sources if is not to be used for an
extended period of time, or during lightening storms.
•The power switch on this product should be set to off before applying mains power via the mains power
cable.
•Some parts of this product, particularly power amplifier components, can become hot to the touch. Do not
touch these parts until they have cooled down.
•Never touch the loudspeaker’s drivers.
•Loudspeakers are often capable of producing a sound pressure level in excess of 85 dB. This may cause
permanent hearing damage so user caution is recommended. Noise exposure is a function of SPL and time, so
observe local regulations when listening at high levels for a long time. Hearing protection may be required.

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O 300 (D) Operating Manual 18
Servicing
•Repairs, maintenance, or other servicing of this product when its interior compartment is exposed should
only be performed by Klein + Hummel authorized service engineers familiar with the equipment and risks
involved in handling electronics.
•Servicing may be required in the event of exposure to unfavorable environmental conditions, such as liquids,
excessive heat, or a lightning strike.
•Amplifier outputs may carry high voltages so take appropriate precautions, for example, connect the cables
before powering up.
•When replacing a fuse, ensure that a brand new fuse is used. It must be exactly the same type, value, and
voltage as the original, as stated in the product’s technical specifications or on the circuit board.
Maintenance and Servicing
•There are no user serviceable parts inside the standard version of this product. Repairs should only be
undertaken by Klein + Hummel certified service engineer.
•Options and accessories are fitted at the user’s own risk.
•Products may be cleaned using a non-abrasive cloth lightly damped with water. Disconnect the mains power
cable when cleaning to avoid risk of electric shock. Do not use alcohol-based cleaners.
•The electronics should only be opened by non-“Klein + Hummel certified service engineer” for the installation
of user installable options as described in the product’s operating manual. The mains power cable should be
disconnected whenever the electronics panel is opened.
•If the main fuse blows, the product should be checked by a Klein + Hummel certified service engineer.
Guarantee
This product comes with a guarantee, a copy of which is enclosed with this product.
Recycling
Attention to product quality in the design phase ensures, firstly, that products have a long life and that, secondly,
all parts of a product may be reused or recycled at the end of that life. An extensive product servicing network
ensures that products can be repaired in the event of the premature failure of a part, or as a way to prolong the
life of a product that would otherwise be considered a candidate for landfill. Eventually there comes a time when
a product is considered beyond repair (for economic reasons or lack of parts), so the parts must be disposed of in
a suitable manner. The disposal should conform to local environmental regulations and be conducted in an
authorized recycling facility.
Loudspeakers and electronic products consist of some or all of these components:
Item Material Recycling Instructions
Loudspeaker Cabinets Wood (MDF), steel, aluminum,
polyurethane or a combination
Separate materials then recycle
Drivers Aluminum, copper, paper and plastics Separate materials then recycle
Damping Materials Sheep or polyester wool Compost
Electronics Panel Aluminum Remove electronics and recycle
Electronics Various Recycle in an approved recycling facility
Remote Electronics Kits Steel and some electronics Separate materials then recycle
Cables and Connectors Metals and/or plastic Reuse or recycle
Packing Material Cardboard, wood and/or plastics Separate materials then recycle
User Manuals and Sales
Literature
Paper and cardboard Recycle