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Hawkins Bass Control
-
Theorv
and Use
dB
HAWKINS
FREQ
BOOST
Q
HAWKINS30-70 Hz
SUBSONIC 13-30 Hz
FIG. 1 BASS CONTROL
Hawkins Bass Control (parametric) is a unique
subwoofer control circuit included with the
Soundstream
RUBICON
Class A 10.2 and 5.2 am-
plifiers. It is capable of removing subsonic energy
in program material while boosting subwoofer fre-
quencies. The circuit consists of two controls. One
adjusts the frequency of operation and the other
adjusts the range of boost. With both controls ad-
justed fully counter-clockwise, no boost is applied
and the amplifier is flat in response down to 20 Hz.
The frequency control (Hz) adjusts
,
o
the starting point of the subsonic fil-
5
ter. On the
RUBICON
Class A 10.2
0
and 5.2, the high pass filter has two
dB
+
frequency ranges. When the bass
1::
control switch is set to “SUB SONIC”,
_20
the high pass filter frequency can be
adjusted from 13 Hz up to a maxi-
-241
I
‘3010
I I
I
I
illll
Frequency {Hz)
50
100
2
mum of 30 Hz. In this setting, no
FIG.
2
VARIABLE “Q”
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 fil-
ter frequency can be adjusted from
30 Hz to a maximum of 70 Hz. In
this setting, there is an available
boost control of 0 to
+9
dB.
!
-20
-25'
-3010
Frequency (Hz)
I
L
50 100
200
tentially harmful low frequencies can
When the Boost is set to 0, Hawkins
acts as a sub-sonic filter only. (See
figure 3) The simple act of removing
po-
dB
Frequency (Hz)
50
100
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)
Application
Subwoofer drivers in qeneral have ex-
I
I
IIII
I
cellent power handling characteristics
over their operational bandwidth. This
-5
bandwidth is determined by many
fat-
dB-lob
tors, including driver design, and en-
closure type. It is possible to overdrive
any subwoofer driver by sending pow-
erful signals outside of its operational
Frequency(Hz)
50
100
FIG.
5
LIMITED EXCURSION
bandwidth. These potentially damag-
ing signals can be removed by adding a subsonic filter. Figure 5 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
“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-
o
tion of boost and cut to suit your de-,,
-5
I
/
I/
/I/I
I I
I
I II
I
signs. So, Hawkins Bass Control can
-lo
provide the “tailoring” needed for any
1::
type of “assisted” design and any woofer
-25
in any type of installation.
-30
Lc_.__.__-
I___~L___1IL1_1Il_____________I
10
Frequency
(Hz)
50
100
200
FIG. 6 VARIOUS SElTlNGS
FIG. 4 VARIABLE BOOST
improve system output by as much as
3
dB.
(see figure 4)
8
9