Other Controls - Klein + Hummel O 300 Operating Manual

Input signal [dBu]
Loudspeaker output for 0 dBu input [dB SPL]
Input gain [dB]
Listening distance [m] (dB change)
Loudspeaker output level [dB SPL]
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:
Crossover
th
Using 4 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.
O 300 (D) Operating Manual
Mains Voltage Fuse (250 V)
220 - 240 V
120 V
100 V
0 (0.775 V) +4 (1.23 V)
96
-5
2 m (-6 dB) 2 m (-6 dB)
85
T 1.6
T 3.15
T 4
Klein + Hummel
96
-9
85
8