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Hawkins Bass Control
-
Theory and
Use
The
RUBICON204,404
and 604 amplifiers incorporates an on-board stag-
gered electronic crossover, with full range RCA outputs to drive an external
amplifier. No external electronic crossover is necessary. The high and low
pass portions of the crossover can be set independently of one another.
In many car audio installations, there is a tendency for a
“midbass
boom.”
Because of their interior dimensions, most
cars will resonate or ring at these
midbass frequencies. If we design the system so there is reduced ouput
in
this region, the final response is very smooth and natural sounding. The
high pass crossover is independently variable from 65 to 220 Hz at 12
dB/
Octave, and low pass crossover is independently variable from 30 to 120 Hz
at 24
dB/Octave.
(12 dB/Octave lowpass on RUBICON204)
For initial crossover setup, try setting the low pass filter to approximately
60 Hz, and the high pass filter to approximately
100
Hz. Change the cross-
over points to accommodate a good mixture of frequency response, power
handling, and personal preference.
12
dB/Octave
High Pass
Hawkins Bass Control (variable) is
a
unique subwoofer control
circuit included with the Soundstream
RUBICON
and 604 am-
plifier. It is capable of removing subsonic energy in program ma-
terial below 45 Hz at 12 dB/Octave, while boosting subwoofer
frequencies. The circuit consists of two controls. One engages a
sub sonic High Pass filter at 45 Hz, and the other adjusts the
amount of boost (0 to
+9
dB).
The Hawkins Bass Control func-
tions on either pair of channels
(l&2
or
38~4)
if their low pass filter
is engaged.
The Boost control adjusts the amount of level applied at the set
---
rll[lj
I
SUB
HANKINS
SON C
l
BASS
CONTROL
HAWKINS
BASS
CONTROL
0
0’
6
.dB
Q
FIG. 1
frequency,
and is adjustable from 0 to
+9
dB
(see figure 2). When the boost is set
to 0, Hawkins Bass Control acts as a sub sonic filter only. The simple act of
removing potentially harmful low frequencies IO
can improve system output by as much as 3
5
dB.
NOTE: The RUBlCON204 contains
O
Hawkins Bass Control
(rixecj)
which is
dB
-5
similiar to the variable version except the
1::
boost is fixed at
+6dB.
-20,
I
I
Application
-25
_
-
.
-
L
I
Subwoofer drivers in general have excellent
-3010
Frequency (Hz) 50 100 200
power handling characteristics over their opera-
FIG. 2 VARIABLE BOOST
tional bandwidth. This bandwidth is determined by many factors, including driver
design, and enclosure type. It is possible to overdrive any subwoofer driver by
sending powerful signals outside of its operational bandwidth. These potentially
damaging signals can be removed by adding a subsonic filter. Figure 3 shows
the effectiveness of the Hawkins Bass Control on woofer excursion in a vented
enclosure. The woofer travels 7.5 mm at 10 Hz. With Hawkins Bass Control
properly adjusted, this excursion can be reduced to less than 1 mm. This is of
great benefit to lowering woofer distortion and increasing output.
Adjustment
An easy method of optimizing your existing
subwoofer enclosure with Hawkin’s Bass
lo
Control is as follows:
.
1.
I
2.
.
.
I
3.
4.
Adjust the boost control to full counter
ds_ji
clock-wise (0) position.
-15
Set the bass control switch to “HAWKINS
-20
BASS
CONTROL”.
:,2,5;
Frequency (Hz) 50
100
200
Play moderate to loud bass material.
FIG. 3 Limited Excursion
Adjust the boost (Q) control until you reach the desired level.
With Soundstream’s Hawkins Bass Control, the boost and frequency control
can provide the “tailoring” needed for any type of “assisted” design and any
woofer in any type of installation.
12
13