Soundstream Technologies 405 - Manual (Page 6)

CROSSOVER ADJUSTMENTS
Hawkins Bass Control Theory and Use
The amplifiers incorporate an on-board staggered electronic cross-
over, with RCA outputs to drive an external amplifier. No external electronic cross-
over is necessary. However, if you do desire to use an external crossover you still
have the option. 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 boom.” Be-
cause of their interior dimensions, most cars will resonate or ring at these
frequencies. If we design the system so there is reduced output 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
and the low pass
crossover is independently variable from 30 to 120 Hz at 24 dB/Octave.
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 crossover points to
accommodate a good mixture of frequency response, power handling, and per-
sonal preference.
12 High Pass
(805 ONLY)
BAND PASS
The can be operated in midrange or “band pass” con-
figuration. In the three way mode, you can tri-amplify with “active” or
midrange to maximize control over individual drivers. The includes
a low pass and high pass filter, which work independent of one another, to
drive the midrange or
speakers.
12 d B/Octave
12 Pass Low Pass Pass
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Hawkins Bass Control (variable) is a unique subwoofer con-
trol circuit included with the Soundstream 805
amplifiers. It is capable of removing subsonic energy in pro-
gram material below 45 Hz at 12 while boosting
subwoofer frequencies. The circuit consists of two controls. One
engages a subsonic High Pass filter at 45 Hz, and the other
adjusts the amount of boost (0 to
The Boost control adjusts the amount of level applied at the
set frequency, and is adjustable from 0 to
(see figure 2).
When the boost is set to 0, Hawkins Bass Control as a sub
sonic filter only. The simple act of removing potentially harmful
low frequencies can improve system output by as much as 3
Application 10
Subwoofer drivers in general have excellent
power handling characteristics over their
operational bandwidth. This bandwidth is de-
termined 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
HAWKINS
SONIC l
BASS
CONTROL
1
3 Frequency (Hz)
FIG. 2 VARIABLE BOOST
nals 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
Bass Control is as follows:
8 0
1. Adjust the boost control to full counter o
clock-wise (0) position. 6 0
SO
2. Set the bass control switch
“HAWKINS BASS CONTROL”. 20
3. Play moderate to loud bass material. ,
4. Adjust the boost (Q) control until you 0 10 200
reach the desired level. FIG. 3 Limited Excursion
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.
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