10
The MFB circuit is comparing the diaphragms movements
with the input signal.
The transducer at the back of the diaphragm monitors the
movement of the diaphragm by measuring the acceleration
of it. In the feedback circuitry the signal is converted to a
signal proportional to the speed. The speed is highest at the
resonance frequency and so is the negative feedback.
Consequently, the woofer receives less power in this area,
and combined with equalization the frequency response
reaches 20 Hz (-6dB).
It would be possible to make a subwoofer this size reach 20 Hz just with pre-
filtering/equalizing, but that would create severe timing problems. This would be heard as
the subwoofer “rumbling” all the time – i.e. not able to start and stop correctly. This might
sound quite “impressive” when listening to surround with a lot of explosions etc., but it is
also the reason why many consumers prefer to turn off the subwoofer when listening to
music - it simply sounds annoying no matter how low you adjust the subwoofer level.
The very powerful amplifier combined with the
MFB
makes the bass reproduction
deep,
precise and detailed.
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.
Cabinets
Due to their compact size and the fact that the cabinets are made of MDF board, they are a
heavy and resonance dead base for the drivers to work in.
The MDF board used for the
D 7LCR
front baffle is 22 mm , the rear baffle is 25 mm, and
the bottom/sides are 19 mm thick.
D 7SUR
has two arrays for the midrange/tweeter and the wood part of the cabinet is made
of 16 mm MDF board.
The cabinet for the
D 7SUB
is made of 25 mm MDF board which makes it very rigid and
resonance dead, contributing to the precise reproduction of the low register.
The finish of the system is Stone Grey with black fabric front.
