7073A Operating Manual Genelec 7073A Active Subwoofer 7073A Active Subwoofer General description Genelec 7073A is a powerful active subwoofer incorporating all the amplifier and crossover electronics needed for bass management and reproduction of low frequency information in modern 6.1 or 5.1 channel surround sound or traditional stereo systems. Its 19 to 120 Hz (±3 dB) frequency range and 124 dB sound pressure output capability are sufficient to handle the most demanding and powerful applications. The low pass section sensitivity can be adjusted from +6 dBu to -12 dBu to allow easy subwoofer level matching with various main speakers. All outputs have 0 dB passband gain. The low pass frequency of the LFE input channel can be set to 85 Hz, 120 Hz or 85 Hz with "Redirect" function that routes LFE content above 85 Hz to the front center monitor. The input sensitivity of the LFE channel can be set to 0 dB or +10 dB. Balanced XLR connectors are used for the system audio inputs and outputs. Two "Bass Roll-Off" switches are included to provide a flat bass response in all acoustical environments, enabling adjustments of the subwoofer response in three -2 dB steps. Two phase matching switches in the crossover allow compensation for the delay which occurs if the subwoofer is placed away from the main speakers, or for other speaker systems phase behaviour. Four settings are provided between 0° and 270°. An 85 Hz test tone generator is included to help achieve accurate crossover phase alignment. Top row LFE IN / SUM IN: Use this connector for the LFE or .1 output channel of a 5.1- or 6.1-channel discrete surround sound source, or the SUM OUT signal from the Installation Each subwoofer is supplied with a mains cable and an operating manual. Once unpacked, place the subwoofer in a suitable location (for more details see the "Positioning" section). Before connecting the audio signals, ensure that both the subwoofer and the main monitors are switched off. Check that the voltage selector switch is set according to your local mains voltage. Audio connections to the subwoofer are made via balanced XLR connectors. An unbalanced source can also be used with a special RCA to XLR cable; the correct connection for the cable is shown in Fig. 2. However, we recommend the use of balanced cables and connectors due to their better noise immunity. The connectors are arranged in three rows on the connector panel (see Fig. 1): Bass management unit The proprietary built-in bass management unit has six signal input and output channels (L/C/R Front and L/C/R Rear), a discrete LFE signal input and a summed signal output, providing great flexibility and easy connection in all monitoring environments. The active crossover contained in the bass management unit splits the input signals into low and high frequency components at 85 Hz. Frequencies below 85 Hz are directed to the subwoofer and frequencies above 85 Hz to the main speakers. Figure 2. XLR to RCA connector for unbalanced operation. Figure 1. 7073A's connector panel, connectors and controls. "master" subwoofer in a daisy-chained multiple subwoofer configuration. Note that the "subwoofer out" channel of an analogue matrix surround decoder (Dolby Surround, Dolby Pro Logic) should not be connected to the "LFE IN" input. See section "Subwoofer in analogue matrix sound systems". SUM OUT: Use this output connector when you want to link another subwoofer to your system. "SUM OUT" carries an unfiltered sum of signals combined from all input channels. See section "Using multiple subwoofers". Middle row FRONT L, C, R CHANNELS IN/OUT: Use these connectors for the Front Left, Center and Right channels of a surround sound system or the Left and Right channels of a Stereo system. Connect line level signal cables from your signal source to their respective "LEFT IN", "CENTER IN" and "RIGHT IN" connectors. Then connect the subwoofer to your main monitors with XLR cables from the "LEFT OUT", "CENTER OUT" and "RIGHT OUT" connectors. All "L, C and R OUT" channels are high pass filtered with the filtering frquency fixed at 85 Hz (12 dB/octave). The placement will affect the phase difference between the main monitors and the subwoofer, and also the bass roll-off rate. These effects can be compensated by the use of the controls in the amplifier unit; but we recommend that at first you leave the switches untouched and concentrate on finding the position where the subwoofer gives the smoothest response, and only then use the controls to fine-tune the balance and phase alignment between the subwoofer and the main monitors. To begin with, place the subwoofer slightly offset from the center of the front wall. The recommended distance to the wall is less than 60 cm / 24" measured from the subwoofer's drivers. This position gives increased acoustic loading (and SPL) due to the proximity of the front wall and floor and avoids low frequency cancellation and comb filtering. Front wall cancellation for the 85 Hz high pass filtered main speakers can be eliminated by placing them at least 110 cm / 43" away from the front wall. In a multichannel system the main monitors should ideally be positioned symmetrically and at an equal distance Bottom row REAR L, C, R CHANNELS IN/OUT: Use these connectors for the Rear Left, Center and Right channels of a surround sound system. The connection is made in the same way as with the Front channels. The rear channels are also high pass filtered at 85 Hz. Once all connections have been made, the subwoofer and main monitors are ready to be powered up. Positioning in the room The placement of the subwoofer in the room affects the overall frequency response and sound level of the system dramatically, as at low frequencies the effects of the room are strong. Even a slight change in the subwoofer's location can make a marked difference in the frequency balance and often patient and methodical experimentation and testing is needed to find the optimum placement. Subwoofer placement Near to a wall 20 cm (8") Bass Roll-Off setting -2 dB -6 dB -2 dB In a corner Flush mounted GENELEC GENELEC GENELEC GENELEC Table 1. Suggested Bass Roll-Off settings Figure 3. Flush mounting the subwoofer. Note the clearance needed on the reflex port side. HEAVY WOODEN OR CONCRETE WALL ABSORBING MATERIAL HEAVY WOODEN OR CONCRETE WALL HEAVY WOODEN OR CONCRETE WALL ABSORBING MATERIAL VIBRATION ISOLATORS f ~ 2-8 Hz VIBRATION ISOLATORS f ~ 2-8 Hz VIBRATION ISOLATORS f ~ 2-8 Hz Figure 4. Flush mounting the subwoofer in a non-absorbing wall. Figure 5. Correct flush mounting in a semiabsorbing wall. Figure 6.Incorrect flush mounting in a semiabsorbing wall. from the listening position (see ITU-R BS.775-1 recommendation for speaker placement for multichannel audio). If the frequency balance is not right, try moving the subwoofer slightly to the left or right so that different room modes are excited at different levels. Positioning the subwoofer close to a corner will boost the bass level at lower frequencies and may cause asymmetrical spatial imaging. If you are using two subwoofers, try placing them asymmetrically relative to the side walls. Sometimes moving the subwoofers apart into the front corners helps with problematic rear wall reflections and the loss of mutual coupling is compensated by the bass boost caused by corner positioning. Although the 7073A subwoofer is magnetically shielded, it may cause some picture distortion if placed near very sensitive video monitors or computer displays. grilles or place the subwoofer so that there is less than 10 centimeters (4") of free space in front of the grilles. The reflex port and connector panel should always have a clearance of at least 20 centimeters (8") to any objects to ensure proper function of the port and cooling for the electronics attached to the connector panel. absorbing front wall structure and the depth of the absorbing material exceeds the depth of the 7073A cabinet, there is a risk of low frequency comb filtering due to the reflections from the wall behind the subwoofer (See Fig. 6.). Setting the input sensitivity The subwoofer requires input sensitivity alignment to the source to obtain a correctly balanced system. The input sensitivity control is located on the connector panel of the subwoofer. An input voltage of -6 dBu with a -6 dBu input sensitivity setting will produce 100 dB SPL @ 1m in free field. To obtain a 110 dB SPL output an input voltage of +10 dBu is required when the input sensitivity is set to 0 dBu. Flush mounting the subwoofer If the 7073A subwoofer is flush mounted into a wall or a cabinet, it is important to ensure unrestricted airflow from the reflex port and cooling for the electronic components. This can be done by making the recess 20 centimeters (8") wider than the subwoofer. Place the subwoofer into the right end of the recess with the drivers' side facing the room. This leaves 20 centimeters (8") of free space on the connector panel and reflex port side. The height and depth of the recess should not be any bigger than those needed to fit the subwoofer flush with the wall surface (See Fig 4-5). If the 7073A is flush-mounted in a semi- Setting the Bass Roll-Off switches The acoustic response of the subwoofer may have to be matched to the characteristics of the room and the positioning in which it will be used. To adjust the subwoofer to match these characteristics use the ''Bass Roll-Off' control switches located on the connector panel. Table 1 Minimum clearances to walls or other objects The power amplifiers are attached to the lower part of the aluminium grilles, which function as a heatsink. Do not cover the Finally, set the -180° phase switch (DIP 4) to the opposite setting and deactivate the test signal. Phase Difference: 0° Phase Difference: 90° 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 85 Hz 85 Hz Phase Difference: 180° Phase Difference: 270° 85 Hz 85 Hz center main monitor while the subwoofer reproduces the frequencies below 85 Hz. Position the microphone at the listening Figure 7. The effect of phase difference between the subwoofer and the main monitors position and adjust the input sensitivity of the subwoofer until frequencies below and above 85 Hz are reproduced at equal level. provides some suggestions for the "Bass Roll-Off" switch settings. When both rolloff switches are set to "OFF", a flat anechoic response is obtained. 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 position which gives the lowest sound level at the listening position. 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 correctly and the frequency analyser should show a smooth response around 85 Hz. 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 available, the following coarse phase matching can be applied. Overload indicators The mode indicator LED on the connector 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 ...