INSTALLATION STEP 9

LSE.Q

THEORY AND USE

LSE.Q is a proprietary subwoofer control circuit included with the Reference705s amplifier. It is capable of both removing subsonic energy in program material and providing a variable boost at low frequencies. The circuit consists of two controls. One adjusts the frequency of operation, and the other adjusts the range of boost. With both controls adjusted fully counter-clockwise, 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 filter. This high

FIG. 1 LSE.Q pass filter can be adjusted from 20 Hz up to a maximum of 60 Hz. This control is useful for setting the lowest frequency that your subwoofer will see. (See figure 1)

The Q control adjusts the amount of boost applied at the set frequency. This is adjustable from .707 (flat) to 2.8 (+9 dB). (See figure 2)

When the Q is set to .707 (Butterworth), LSE.Q acts as a sub-sonic filter only. (See figure 3)

The simple act of removing the signal below the vented tuning frequency can improve system output by as much as 3 dB. With Q values greater than .707, boost is added in addition to the sub-sonic filter. (see figure 4)

10

 

 

 

 

5

Q=2.8

 

 

 

0

 

 

 

 

-5

 

 

 

 

dB

 

Q=0.707

 

 

-10

 

 

 

-15

 

 

 

 

-20

 

 

 

 

-25

 

 

 

 

-3010

Frequency (Hz)

50

100

200

Application

 

 

 

 

 

 

 

 

 

 

 

FIG. 2 Variable “Q”

 

 

 

 

 

 

 

 

 

 

 

 

10

 

 

 

 

Woofers in vented enclosures have good power handling characteristics

 

 

 

 

5

 

 

 

 

above

the tuning frequency, but below

the

tuning

frequency,

power

0

 

 

 

 

-5

 

 

 

 

handling drops

off considerably.

This

is

due

to

the loss

of any dB

 

 

 

 

-10

 

 

 

 

appreciable resistive

air mass.

At

frequencies below resonance,

the

 

 

 

 

-15

 

 

 

 

 

 

 

 

 

woofer starts to behave as if it were

 

 

 

 

8.0

 

 

 

 

-20

 

 

 

 

7.0

 

 

 

 

mounted in “free-air”. If we wish to

-25

 

 

 

 

 

 

 

 

 

 

 

 

 

6.0

 

 

 

 

improve

the

performance

of

a

-3010

Frequency (Hz)

50

100

200

5.0

 

 

 

 

 

 

 

 

vented system, we should remove

 

 

 

 

 

Xd

 

 

 

 

 

FIG. 3 Variable High Pass

 

(mM) 4.0

 

 

 

 

 

 

 

 

 

 

these

unwanted

signals from

our

 

 

 

 

 

3.0

 

 

 

 

 

 

 

 

 

2.0

 

 

 

 

system. These can be removed by adding the subsonic filter. Figure 5

 

 

 

 

 

1.0

 

 

 

 

shows the effectiveness of LSE.Q on woofer excursion. Woofer travel is

0.010

 

 

 

 

Frequency (Hz)

50

100

200

7.5 mm at 10 Hz, with LSE.Q properly adjusted, this excursion can be

 

FIG. 5 Limited Excursion

 

reduced to less than 1 mm. This is of great benefit to lowering woofer

 

 

 

 

 

distortion and increasing output.

 

 

 

 

 

 

 

10

 

 

 

 

 

5

 

 

 

 

Adjustment

0

 

 

 

 

-5

 

 

 

 

An easy method of optimizing your existing subwoofer enclosure with

dB

 

 

 

 

-10

 

 

 

 

 

 

 

 

 

LSE.Q's “Hz” control is as follows.

-15

 

 

 

 

-20

 

 

 

 

 

 

 

 

 

1. Adjust frequency and boost control to full CCW position.

-25

 

 

 

 

 

 

 

 

 

2. While listening to music with strong bass content at a moderate level,

-3010

Frequency (Hz)

50

100

200

 

FIG. 4 Variable “Q”

 

 

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.

 

 

 

 

 

Soundstream’s LSE.Q contains the same type of circuit with the added benefit of infinite adjustability. Our “Q” and “Hz” controlcan provide virtually any combination of boost and cut to suit your designs. So, LSE.Q can

17

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Soundstream Technologies 705s owner manual LSE.Q Theory and USE, Application
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705s specifications

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