Soundstream Technologies 805, 405 Hawkins Bass Control - Theory and Use, Crossover Adjustments

CROSSOVER ADJUSTMENTS

Hawkins Bass Control - Theory and Use

The RUBICON 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 “midbassboom.” Be- cause of their interior dimensions, most cars will resonate or ring at these midbass 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 dB/Octave, 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

Hawkins Bass Control (variable) is a unique subwoofer con- trol circuit included with the Soundstream RUBICON & 805 amplifiers. It is capable of removing subsonic energy in pro- gram material below 45 Hz at 12 dB/Octave, 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 +9 dB).

The Boost control adjusts the amount of level applied at the set frequency, and is adjustable from 0 to +9 dB (see figure 2). When the boost is set to 0, Hawkins Bass Control a,cts as a sub sonic filter only. The simple act of removing potentially harmful low frequencies can improve system output by as much as 3 dB.

HAWKINS

SUB • BASS

SONIC CCNTRl3L

HA’tVKINS I EASS

CONTROL

FIG. 1 ’

accommodate a good mixture of frequency response, power handling, and per- sonal preference.

12 dB/Octave High Pass

2-WAY

39WAY (805 ONLY)

MIDBASS/MIDRANGE BAND PASS

The RUBICON can be operated in midrange or midbass “band pass” con- figuration. In the three way mode, you can tri-amplify with “active”midbass or midrange to maximize control over individual drivers. The bandpass includes a low pass and high pass filter, which work independent of one another, to drive the midrange or midbass speakers.

	12 d B/Octave
12 dB/Octave High Pass	Low Pass 1 High Pass

39WAY

Application	10
Subwoofer drivers in general have excellent 5
power handling characteristics over their z
operational bandwidth. This bandwidth is de- dB.,0
termined by many factors, including driver -15
design and enclosure type. It is possible to -20
overdrive any subwoofer driver by sending I’,:
powerful signals outside of its operational		3	Frequency (Hz)
			FIG. 2 VARIABLE BOOST
bandwidth. These potentially damaging sig-

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 Hawkin’s Bass Control is as follows:

1. Adjust the boost control to full counter	8 0
	7 o
clock-wise (0) position.	6 0
	SO
2. Set the bass control switch totmzbO
“HAWKINSBASS CONTROL”.	20
3. Play moderate to loud bass material.	20
	, o
4. Adjust the boost (Q) control until you	Cl 0 10 Frequency	(Hz'l	50	100	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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