Genelec 1094A Setting the Phase Control, Coarse Phase Correction Method, Subwoofer Bypass Control

Setting the Phase Control

The effect of incorrect phase alignment between main monitors and subwoofer is a drop in the frequency response of the whole system at the crossover frequency. The graphs below (figure

3)show the effect of phase difference on the frequency response.

The phase difference between the main monitors and subwoofer at the listening position is dependent upon the position of the subwoofer in the listening room. For accurate system alignment in the room acoustic

Coarse Phase Correction Method

The method to coarse align the phase of the system is as follows.

•Connect an audio frequency signal generator to one of the channels used in the system. If the signal generator has an unbalanced output use a cable with pin 3 grounded to pin 1 at the input as shown in figure 4 below.

CABLE 2 1

Connect a high grade measuring microphone to the analyser and feed pink noise into the left main monitor. Position the microphone at the listening position and adjust the input sensitivity of the subwoofer until frequencies below and above 85 Hz are reproduced with equal level. Then adjust the phase control switches until a clear dip of at least -6dB can be seen at the crossover frequency (85 Hz).

If a dip appears at several switch positions select the one that gives the

measuring equipment is required. If this equipment is not available to the

RCA

SCREEN

3

XLR

deepest reading. This should be the case where the phase difference

user coarse phase matching can be applied.

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MALE

Figure 4. XLR to RCA connector for unbalanced operation.

•Set the frequency generator to 85Hz. If a signal generator is not available then it is possible to use an audio test recording with a test frequency in the range 70Hz to 100Hz.

between the subwoofer and the main monitors is at a maximum. To change the phase difference to a minimum the -180° switch should be moved to the opposite setting. The frequency analyser should now show the smoothest response around 85 Hz and the phase should now be set correctly. Repeat the above procedure with the right channel and possible centre channel main monitors.

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•Toggle the -180° phase
switch 'on' and 'off' and set
		it		4
to the position which gives			3
				2
the lowest sound level at the	ON
				1
listening position.
• Next toggle the -90° phase			4
switch 'on' and 'off', and again				3
set it to the position which
	ON			1 2
gives the lowest sound level.
• Finally, set the -180° phase
				3 4
switch to the opposite setting.
				2
	ON			1

Subwoofer Bypass Control

A bypass control feature is included into the subwoofer circuits so that the effect of the subwoofer on the whole monitor system can be determined. With the bypass switch on, the high pass filters for the main monitors are bypassed and the system behaves as if the subwoofer were not connected. The bypass remote controller is inserted into the ¼ inch jack socket located on the rear amplifier panel. See figure 5 for construction details.

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Figure 3. The effect of phase difference between the subwoofer and the main monitors

Phase Correction Method with Test Equipment

If a frequency analyser and a pink noise generator are available then the following procedure can be used to match the phasing between the subwoofer and the main monitors.

Mono ¼ inch

Jack Socket

SPST Switch

Figure 5. Bypass Remote Switch Construction.