Digital Monitoring Products 7073A Especificaciones descargar pdf (Pagina 5)

provides some suggestions for the "Bass

Roll-Off" switch settings. When both roll-

off switches are set to "OFF", a flat ane-

choic response is obtained.

Setting the phase control

Incorrect phase alignment between main

monitors and subwoofer causes a drop

in the frequency response of the whole

system at the crossover frequency. The

graphs above (Fig. 7) show the effect

of phase difference to the frequency

response.

The phase difference between the main

monitors and subwoofer at the listening

position is dependent upon the position

of the subwoofer, so the phase adjustment

should be done only after the preferred

position is found. Acoustic measuring

equipment is required for accurate system

alignment. If this equipment is not avail-

able, the following coarse phase matching

can be applied.

Coarse phase adjustment

method

Genelec 7073A subwoofer is equipped

with a built-in 85 Hz frequency test tone

generator to accomodate easy phase

alignment. The test tone generator is

connected to the subwoofer's "FRONT

CENTER OUT" channel only. In a stereo

system it is necessary to temporarily

connect either of the channels to this

output.

Power up the system and set the DIP

switches 3 (SUM IN MODE) and 4 (LFE

+10 dB) on the first switch group to "ON"

Now you should hear an 85 Hz test

signal from the subwoofer and the main

monitor connected to the center channel

output.

Toggle the -180° phase

switch (DIP 4 on the second

switch group) on and off,

and set it to the position

which gives the lowest

sound level at the listening position.

Next toggle the -90° phase

switch (DIP 3) on and off,

and again set it to the posi-

tion which gives the lowest

sound level at the listening

position.

Figure 7. The effect of phase difference between the subwoofer and the main monitors

Finally, set the -180° phase

switch (DIP 4) to the oppo-

site setting and deactivate

the test signal.

Phase correction method

with test equipment

The following procedure matches the

phase between the subwoofer and the

main monitors using a frequency analyser

and a pink noise generator. Connect a

high grade measuring microphone to the

analyser and feed pink noise into the

"CENTER IN" input of the subwoofer. The

subwoofer's bass management system will

direct the frequencies above 85 Hz to the

center main monitor while the subwoofer

reproduces the frequencies below 85 Hz.

Position the microphone at the listening

position and adjust the input sensitivity of

the subwoofer until frequencies below and

above 85 Hz are reproduced at equal level.

Then adjust the phase control switches for

the maximum dip of at least -6 dB at the

crossover frequency (85 Hz).

Change the -180° switch to the opposite

setting. The phase should now be set cor-

rectly and the frequency analyser should

show a smooth response around 85 Hz.

Overload indicators

The mode indicator LED on the connec-

tor panel will turn from green to yellow to

indicate clipping and then to red to indicate

that the protection circuit has activated. If

this occurs frequently, reduce the input

level to the subwoofer until the LED

remains green.

If the LED on the connector panel is not

easily visible, the optional Remote LED Kit

can be used to bring it into view. The kit

consists of a LED in a compact case and

an RJ11 cable to connect the case and

the "REMOTE" RJ11 connector on the

connector panel.

Subwoofer bypass control

A bypass control feature is included in

the subwoofer circuits so that the effect

of the subwoofer on the whole moni-

Phase Difference: 0°

85 Hz

Phase Difference: 180°

85 Hz

Phase Difference: 270°

85 Hz

Phase Difference: 90°

85 Hz

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