26
| KH 805
Technical information & glossary
Absolute
level
In Europe, the absolute level of 0 dBu is
-
18 dBFS (EBU standard R68) . In the US, +4 dBu is
-
20 dBFS
(SMPTE standard RP155) . These dBu values should lead to the following sound pressure levels:
Application
Sound pressure level
Film
85 dB(C)
Broadcast
79 dB(C) (reference level)
Music
No defined reference levels
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 log
10
(
r
), however this may not always be the case .
Absolute voltage level of input signal
0 dBu
(0 .775 V)
+
4 dBu
(1 .23 V)
Setting SUBWOOFER GAIN | INPUT GAIN
J
-
1 dB
-
5 dB
Setting SUBWOOFER GAIN | OUTPUT LEVEL
H
100
100
Listening distance [m] (dB change)
5 m (
-
14 dB)
5 m (
-
14 dB)
Measured output level in dB SPL at 1 m
85 dB SPL
85 dB SPL
Maximum input signal before activation
of the protection system
17 dBu
17 dBu
Absolute acoustic level calibration for signal channels is generally achieved using a sound level meter
set to “C-weighted” and “Slow” . 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 posi-
tion . Then adjust each channel’s source level, not the loudspeakers and subwoofer(s) so that the
above stated sound pressure levels are achieved .
Acoustical
axis
The acoustical axis is a line perpendicular to the subwoofer’s front panel along which the microphone
was placed when tuning the subwoofer’s crossover during design . The acoustical axis is located at
the midpoint of the KH 805’s bass driver . Note that the subwoofer emits very low frequencies which
are emitted omnidirectionally . That is why the orientation of the subwoofer cabinet in the room does
not matter .
Acoustical
controls
The acoustical controls are low-order analog filters designed to compensate for some of the acoustical
issues commonly found in listening environments . The acoustical controls’ settings will depend on
the subwoofer’s location and will probably be different for the same subwoofer type positioned in dif-
ferent locations in the same room . When calibrating subwoofers there are three areas requiring atten-
tion: in-room response, level relative to main loudspeakers, and phase relative to main loudspeakers .
