@1m with -6 dBu input level. To get the full
output level of 120 dB SPL from the HT315B
an input level of +14 dBu is needed at this
setting. Respectively, the full output level of
the HT312B is reached at an input level of
+10 dBu.
Autostart and remote control
The RAM4 and RAM5 amplifiers are
equipped with an “Autostart” function, which
automatically turns the amplifier to “standby”
mode if an input signal has not been detected
for approximately thirty minutes, and back
to “on” mode when the signal returns. The
function can be deactivated by turning the
“AUTOSTART” dip switch on the amplifier
back panel to “OFF”.
The amplifier power can also be switched
by a remote control unit connected to the
respective inputs on the amplifier back panel.
Two pairs of connectors are provided, 1 and 2
for a 12 V DC type remote control, and 3 and
4 for an external switch or relay type control.
Do not connect two remote controls to the
loudspeaker at the same time. Activate the
function by turning the "REMOTE CONTROL"
dip switch on the amplifier control panel to
"ON". Note that the remote control function
overrides the “autostart” dip switch function.
Setting the tone controls
The acoustic response of the system may
also have to be adjusted to match the acoustic
environment. The adjustment is done by set-
ting the five tone control switch groups ‘bass
tilt’, ‘bass roll-off’, ‘bass level’, ‘mid level’ and
‘treble level’ on the control panel of the ampli-
fier. The manufacturer’s default settings for
these controls are ‘All Off’ to give a flat ane-
choic response. See Table 2 for suggested
tone control settings in differing acoustic envi-
ronments. Figures 7 and 8 show the effect
of the controls on the anechoic response.
Always start adjustment by setting all switches
to the ‘OFF’ position. Then set only one switch
per group to the ‘ON’ position to select the
response curve required. If more than one
switch is set to ‘ON’ (within one switch group)
the attenuation value is no longer accurate.
Vertical / horizontal mounting
The loudspeakers are delivered either for
vertical or horizontal mounting. In the hori-
zontal mounting position the bass drivers
should point inwards to obtain better low
frequency coupling. If the loudspeaker posi-
tioning needs to be changed, the DCW plate
can be rotated so that the midrange driver
remains always located at the bottom of the
DCW. Remove the four corner screws of the
DCW and pull the plate carefully out without
stressing the wires and the gasket. Rotate
the plate 90 degrees in the appropriate direc-
tion and remount the screws.
Flush mounting
The HT312B and HT315B can be used flush
mounted into the wall structure, which offers
some acoustical benefits. No cabinet edge
diffraction will occur, resulting in an improved
response, especially at midrange frequen-
cies. Low frequency reflections from the wall
behind the loudspeaker can be avoided, which
improves the low frequency response and effi-
ciency and allows the loudspeaker to work in
half space conditions. In terms of installation
and orientation, the loudspeaker’s acoustical
axis (See Figure 1.) should also point directly
to the the reference listening position. The
loudspeakers should be vertically aimed so
that the acoustical axis of the loudspeakers
meet around ear height at the reference listen-
ing position. In the horizontal plane the loud-
speaker should be positioned according to the
standard stereophonic (60 degrees between
left-right channels) or multichannel (ITU-R
BS.775-1) placement recommendation.
Loudspeaker mounting
position
Bass
roll-off
Bass
tilt
Bass
level
Midrange
level
Treble
level
Free anechoic response
None
None
None
None
None
Free standing in a
damped room
None
-2 dB
None
None
None
Free standing in a
reverberant room
None
-2 dB
-2 dB
None
None
In a corner
-2 dB
-2 dB
-2 dB
None
None
Flush mounted
None
None
-4 dB
None
None
Table 2. Suggested tone control settings for different acoustic environments
H1 mm (in)
W1 mm (in)
H2 mm (in)
W2 mm (in)
HT312B
540 (21
1
/
4
")
200 (7
7
/
8
")
230 (9
1
/
16
")
170 (6
11
/
16
")
HT315B
650 (25
5
/
8
")
240 (9
1
/
2
")
282 (11
1
/
8
")
202 (7
15
/
16
")
Figure 1. Location of the acoustic axis
Figure 2. RAM4 amplifier connectors and controls. RAM5 is similar
except that it has no voltage selector.
