Soundstream Technologies 255 - Manual (Page 8)

Hawkins Bass Control Theorv and Use
Hawkins Bass Control (variable) is a unique subwoofer control
circuit included with the Soundstream
amplifier. It
is capable of removing subsonic energy in program material be-
low 45 Hz at 12 dB/Octave, while boosting subwoofer frequen-
cies. 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 (fixed at for the 355).
The Boost control adjusts the amount of level applied at the
frequency, and is adjustable from 0 to
(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 fre-
quencies can improve system output by as much as 3
Application
Subwoofer drivers in general have excel-
lent power handling characteristics over
their operational bandwidth. This bandwidth
is determined by many factors, including
HAWKINS
INSTALLATION STEP 1
SELECTING THE SPEAKER OUTPUT MODE
Channels 1 through 4 of the 355 555 amplifiers have the ability
to operate in any one of the following modes:
(Stereo /Mixed Mono): Use this mode for 5 channel stereo operation (all
channels) or for Mixed Mono operation_
3CH Mono): Use this mode to bridge channels and outputs for
3 channel operation.
Please follow the wiring schemes below for the correct operation:
driver design and enclosure type. It is pos-
sible to overdrive any subwoofer driver by
sending powerful signals outside of its op-
I
I . 1
!
erational bandwidth. These potentially dam-
50 100
aging signals can be removed by adding a
FIG. 2 VARIABLE BOOST
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 (555 on/y)
An easy method of optimizing your existing subwoofer enclosure with Hawkins
Bass Control is as follows:
1 0
1. Adjust the boost control to full counter
clock-wise (0) position.
-5
-10
2. Set the bass control switch to
“HAWKINS BASS CONTROL”.
3. Play moderate to loud bass material.
0 (Hz) 50 100 230
4. Adjust the boost (Q) control until you
FIG. 3 Limited Excursion
reach the desired level.
STEREO
R + L +
--- - - -
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.
15