Input Stage; Acoustical Controls - KLEIN+HUMMEL O 410 Mode D'emploi

Input Stage

The standard input stage is a 14 kΩ electronically balanced type on a female XLR socket.
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 input ground lift switch to disconnect the audio ground, on pin 1 of the analog XLR input, from the
electronics' chassis ground. For safety reasons, the electronics chassis ground is always connected to the
mains power earth pin.
•
Fit an optional transformer balanced input stage to the loudspeaker. 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.
In addition, it is possible to fit a 24-bit, 192 kHz digital input stage. It has XLR and BNC inputs, and a BNC output,
so it is possible to have analog and digital signals simultaneously connected; the selector switch is used to
monitor the selected input.

Acoustical Controls

The acoustical controls are low-order analog filters designed to compensate for some of the acoustical issues
commonly found in listening environments. There is either a Low Mid or Mid control depending on the
loudspeaker model. The other controls are seen on all three-way systems.
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, -2.5, -5, and -7.5 dB.
The mid control (O 410) is used to compensate for strong first order reflections (floor, ceiling, side walls), that
may cause an aggressiveness in the midrange sound quality. A high mid-band reverberation time can also have
this effect and thus be compensated. Four settings are available: 0, -1.5, -3, and -4.5 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: +1, 0, -1, and -2 dB.
Operating Manual O 410
Pin Signal
1 Audio Ground
2 Positive
3 Negative
English
Klein + Hummel
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