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KVER
SONIC
HAWKINS
BASS
CONTROL
r
HAWKINS
1
FREQ FREQ
BOOST
110
FIG. 1 BASS CONTROL
Hawkins Bass Control (parametric)
is a unique
subwoofer control circuit included with the
Soundstream RUBICONSM, 702
and 1002
am-
plifiers. It is capable of removing subsonic en-
ergy in program material while boosting
subwoofer frequencies. The circuit consists of
two controls. One adjusts the frequency of op-
eration and the other adjusts the range of boost.
With both controls adjusted fully counter-clock-
wise, no boost is applied and the amplifier is flat
in response down to 20 Hz.
The frequency control (Hz)
adjusts
the starting point of the subsonic fil-
ter. On the RUBICON502,702 and
1002, the high pass filter has two fre-
quency ranges. When the bass con-
trol switch is set to “SUB SONIC”,
the high pass filter frequency can be
adjusted from 13 Hz up to a maxi-
mum of 30 Hz. In this setting, no
boost “Q” control is available. This
control is useful for setting the low-
est frequency that your subwoofer
will see (see figure 1). When the
bass control switch is set to
“HAWKINS BASS CONTROL”, the
high pass filter frequency can be ad-
justed from 30 Hz to a maximum of
70 Hz. In this setting, there is an
available boost control of 0 to
+9
dB.
10
1
I
I
5
0
-5
dB
-10
-15
-20
-25
I
I
-3010
Frequency
(Hz)
I
IIIIIII
1
50 100 200
FIG. 4 VARIABLE BOOST
10
5
0
-5
dB
-10
-15
-20
-25
-30
10
5
0
-5
dB
-10
-15
-20
-25
-30
lOFrequency
50 100
200
FIG. 2 VARIABLE
“Q”
10
Frequency(Hz)
FIG. 3 VARIABLE HIGH PASS
The Boost control
adjusts the amount
of level applied at the set frequency.
This is adjustable from flat
(OdB)
to
+9
dB.
(See figure 2)
When the Boost is set to 0, Hawkins
acts as a sub-sonic filter only. (See
figure 3) The simple act of removing
potentially harmful low frequencies
can improve system output by as
much as 3
dB.
(see figure 4)
10
Application
Subwoofer drivers in general have
excellent power handling character-
istics over their operational band-
width. This bandwidth is determined
by many factors, including driver de-
sign, and enclosure type. It is pos-
sible to overdrive any subwoofer
driver by sending powerful signals
80
70
60
5.0
(,?I$0
30
20
IO
0.0
10
Frequency(Hz)
50
100
200
FIG. 5 LIMITED EXCURSION
outside of its operational bandwidth. These potentially damaging signals
can be removed by adding a subsonic filter. Figure 5 shows the effective-
ness of the Hawkins Bass Control on woofer excursion in a vented enclo-
sure. 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 “Hz” control is as follows.
1.
Adjust frequency and boost control to full CCW position.
2.
Set the bass control switch to “HAWKINS BASS CONTROL”.
3.
While listening to music with strong bass content at a moderate level,
slowly adjust frequency control clockwise. Listen for a reduction of bass
response. Now, rotate frequency control slightly backwards. This serves
the purpose of removing the “subsonic” bass energy.
With Soundstream’s Hawkins Bass
Control, the boost and frequency con-
trol can provide virtually any combina-
tion of boost and cut to suit your de-
signs. So, Hawkins Bass Control can
provide the “tailoring” needed for any
type of “assisted” design and any
woofer in any type of installation.
11
10
5
0
-5
dB
-10
-15
-20
-25
-30
10
Frequency(Hz) 50 100
200
FIG. 6 VARIOUS SETTINGS