JAMO D 4 - Manual (Page 11)

11
(Sub)Woofer
The 8” woofer features a vented magnet system and a Ø 38 mm / 1½” aluminium voice coil
former. The 4-layer voice coil is 28 mm / 1.1” long allowing linear excursions up to +/- 10
mm / 0.4” – and still with >70% of the B*L product available!
The magnet system features a vented pole piece in
order to avoid over/under pressure behind the dust
cap (mechanical damping) when the cone is moving.
The cone is made from air-dried paper. Normally
when making paper cones, the water is pressed out of
the cone simply because letting it air-dry is way too
time consuming.
However, there is a quite significant advantage from
spending the extra time. When letting the paper air-
dry, the cone is approximately double thickness
compared to a pressed cone. Still the low weight is
maintained, but due to the increased cone thickness,
it is simply more rigid – an extremely important
feature for a long throw woofer that is going to be fed
by a 400 W amplifier . . .
The foam surround allows fast movement at its low frequency working range.
Electronics (D 4SUB)
Amplifier
The D 4SUB features a 400 Watt Class D amplifier that
operates at a highly efficient 85%. This means that 85% of
the power consumption is dedicated to the speaker, and
only 15% is dissipated as heat.
It is manufactured from SMD components. The
advantages are that signal paths are kept very short and
that the electronics is much more resistant to the shocks
and vibrations that arise inside a subwoofer. The results
are better sound and a prolonged lifetime for the
subwoofer.
Auto On/Off
Forget all about the subwoofer once it is connected as this feature automatically sets the
subwoofer in stand-by after approximately 20 minutes without input signal.
The “start up” sensitivity is 3mV and it stays on as long as the signal is above 1mV.
Phase and Cut-off controls
Place the subwoofer where it is most convenient - the controls ensure that the sound from
the subwoofer can be adjusted to blend seamlessly with the sound from the rest of the
speakers.