One of the biggest problems with today’s subwoofers is their integration to the main or satellite speakers. The problem gets even hairier when multichannel in a surround setup enters the equation. The key to this dilemma lies in the phase relationship of subwoofer to main speakers at the crossover frequency. Genelec has addressed this problem to some extent with the bass management system in its LSE series of powered subwoofers.
Product PointsApplications: Studio, post production
Key Features: 12-inch woofer; Laminar Spiral Enclosure; onboard 250W amplifier; bass management controls
Contact: Genelec at 508-652-0900, Web Site.
The LSE (Laminar Spiral Enclosure) is a long sheet metal spiral with a large cross-sectional area that has been wound into an enclosure with a good size vent at the bottom. Such a vent allows the movement of large amounts of air at low velocity, which is said to maintain a constant frequency response over the full range of low frequencies.
The 7070A ($2,395) is a single 12-inch active system and is in the middle of the LSE line of subwoofers with the smaller 7060A single 10-inch and big brother 7071A with dual 12-inch drivers. The 7070A is powered by an internal 250W amplifier and is rated ±3 dB from 19 Hz to 120 Hz with an 18 dB per octave subsonic filter below the 19 Hz lower limit. Physically, the 7070A measures 25 inches x 22 inches x 20 inches and weighs in at a hefty 110 pounds. Two steel rod handles from the solid front 2-inch thick surface to the back 2-inch thick surface makes for fairly easy maneuvering (considering the weight) as all of the corners are rounded and can be slid or rolled around by one person with no trouble.
The built-in bass management system has six inputs and outputs for L/C/R front and L/C/R rear plus a discrete LFE input and a sum output which carries the unfiltered sum of all the inputs for driving multiple subwoofers. All of the inputs and outputs are balanced with XLR connectors. The six main outputs are high-pass filtered at 85 Hz with a 12 dB per octave slope while the frequencies below 85 Hz are low-passed and feed directly to the subwoofer. I have found 85 Hz to be a good frequency to high-pass using small two-way main speakers, as they do not have to work as hard trying to produce the lower frequencies. This usually results in lower distortion and increased headroom because of reduced cone excursion. Also by rolling LF off the mains you are not trying to reproduce some of the same frequencies with the sub and the mains, which can result in phase cancellation problems.
That said, it is still a real challenge trying to seamlessly mate sub to main. To me the biggest problem is always where to place the subwoofer, since they are not small and need to fit in with the other components. Once a suitable location is established, Genelec has provided a clever way to get the sub/main phase alignment in the ballpark by using two DIP switches and a built-in 85 Hz oscillator.
The test tone generator is connected to the subwoofer’s Front Center Out channel, so in a stereo system it is necessary to temporarily connect either the left or right speaker to this output (not perfect but it seems to work). Once the oscillator is turned on you toggle the 180-degree phase switch on and off, and set it to the position which gives the lowest sound level at the listening position. Next you toggle the 90-degree phase switch on and off and again set it to the position which gives the lowest sound level. Finally set the 180-degree phase switch to the opposite setting and deactivate the test signal. I found that this procedure works well in getting the subwoofer set up initially. Then go back and make small sub location changes for finer tuning.
An input sensitivity control is provided to match subwoofer level to main output while a pair of bass rolloff DIP switches allows for -2 dB, -4 dB or -6 dB attenuation of the lowest frequencies when the subwoofer is flush mounted, placed near a wall or in a corner.
The 7070A has a nice bypass control feature that allows you to listen without the effects of the subwoofer or the high-pass filtered main speakers. Both 1/4-inch and RJ11 connectors are provided so that you can activate the bypass from the listening position. Nice feature.
I first tried to set up the 7070A with three ceiling mounted Thiel Power Point speakers (PAR 5/03) . I use the Thiels for surrounds in my setup because they work better than any floor speaker I have tried while giving me more space. In this instance the Power Points were connected as front speakers – which I knew would be a challenge integrating to a subwoofer, but the idea of a full-range system without speaker stands was very appealing and since the Power Points are basically flat down to 70 Hz or so, it seemed like it could work. Not.
No matter where I placed the subwoofer I could not get the transition from main to sub without some sort of cancellation, regardless of DIP switch settings. Maybe it was just asking too much to integrate ceiling main speakers with a subwoofer on the floor, but it was worth a try.
Next I set up the 7070A with my reference SLS S8R monitors on RPG stands, placing the sub between the left and center front speaker. Using the built-in oscillator I went through the DIP switch phase routine and it worked as well as any sub I have tried with these speakers. Close but no cigar, the integration was not bad, but because the S8Rs go down to 40 Hz in my room, I preferred the less extended but more cohesive sound without the subwoofer.
Finally, I tried the 7070A with a pair of the new Genelec 6040A stand-mounted 7-inch two-way powered speakers. Not as familiar to the pro world as the home theater market, the 6040As are beautifully made with rounded corners and integrated stands. The two 120W amplifiers are located in the base and the total height of the system is almost exactly one meter. Like the Genelec pro speakers, the 6040As have a similar amplifier setup with DIP switches for bass tilt, rolloff and treble tilt. I set all of the switches to off – the factory default setting, placed the subwoofer between them and voila! The integration was as good as I have heard any subwoofer integrate to main speakers. When switched to the Bypass mode you could hear the 7-inch woofers of the 6040As working overtime trying to reproduce the lower bass frequencies. With the sub switched in, the bass extended another octave or more and the upper bass became cleaner and more articulate.
The integration from top to bottom was smooth and seamless, something you rarely hear in a sub/satellite setup. I see no reason why the 7070A would not work equally well with any of the Genelec pro speakers, especially the two-way 1030As and the 1031As. Genelec engineers have done their homework on this subwoofer, providing good solid bass down to 20 Hz and a flexible bass management system that really works. When you consider all of the features and the quality of this subwoofer, the price tag of $2,395 is not out of line.