17
Connection of HELIX U 8A / U 10A to the head
unit / car radio:
Caution:
Carrying out the following steps will re-
quire special tools and technical knowledge. In or-
der to avoid connection mistakes and / or damage,
ask your dealer for assistance if you have any ques-
tions and follow all instructions in this manual (see
page 11 et sqq.). It is recommended that this unit
will be installed by an authorized HELIX dealer.
1. Connecting the highlevel speaker inputs
The highlevel loudspeaker inputs L and R can
be connected directly to the loudspeaker out-
puts of an OEM or aftermarket radio using
appropriate cables (loudspeaker cables with
1 mm² / AWG 18 max.).
Actually it is not mandatory to use both highlev-
el speaker inputs. However, we recommend the
following channel assignment:
Channel L = Front left
Channel R = Front right
Make sure that the polarity is correct. If one
connection has reversed polarity it may affect
the performance of the active subwoofer and
the sound reproduction may be completely sup-
pressed.
When using this input, the remote input (REM)
does not need to be connected as the active
subwoofer will automatically turn on once a
loudspeaker signal is applied.
Important:
It is strictly forbidden to use the
High level Input
and lowlevel
Line Input
at the
same time. This may cause severe damage to
the lowlevel line outputs of your car radio.
2. Connecting the lowlevel line inputs
Use the correct cable (RCA / Cinch cable) to
connect these inputs to the lowlevel line outputs
of your car radio. It is not mandatory to use both
lowlevel line inputs. However, we recommend
to use both inputs.
The automatic turn-on circuit does not work
when using the lowlevel line inputs. In this case
the remote input (REM) has to be connected to
activate the HELIX U 8A / U 10A.
3. Adjustment of the input sensitivity
Attention:
It is mandatory to properly adapt
the input sensitivity of the U 8A / U 10A to
the signal source in order to avoid damage
to the active subwoofer.
If you want to change the input sensitivity use
the
Input Level
control (see page 14, item 6).
The setting of the control affects both the low-
level line inputs (
Line Input
) and the highlevel
speaker inputs (
Highlevel Input
)!
4. Connection to power supply
Make sure to disconnect the battery before
installing the HELIX U 8A / U 10A!
Connect the +12 V power cable to the positive
terminal of the battery. The positive wire from
the battery to the power terminal of the active
subwoofer needs to have an inline fuse at a dis-
tance of less than 12 inches (30 cm) from the
battery.
The value of the fuse is calculated from the
maximum total current draw of the whole car
audio system (U 8A / U 10A = max. 25 A RMS
at 12 V power supply). If your power wires are
short (less than 1 m / 40”) then a wire gauge of
4 mm² / AWG 12 will be sufficient. In all other
cases we recommend a gauge of 6 mm²/ AWG
10!
The ground cable (same gauge as the +12 V
wire) should be connected to a common ground
reference point (this is located where the neg-
ative terminal of the battery is grounded to the
metal body of the vehicle), or to a prepared met-
al location on the vehicle chassis, i.e. an area
which has been cleaned of all paint residues.
5. Connecting the remote input
The remote input (REM) has to be connected to
the radio remote output if the active subwoofers
lowlevel line inputs are used as signal inputs.
We do not recommend controlling the remote
input via the ignition switch to avoid pop noise
during turn on/off.
If the
Highlevel Input
is used this input does not
need to be connected as long as the car radio
has BTL output stages.
