Subwoofer Guide
Subwoofers can be a wonderful addition to provide improved bass reproduction for compact loudspeakers. Most are active; passive ones are rare. Active subwoofers require a separate power supply and have their own amplifier.
It's important to remember that with loudspeakers, placement is key. (We covered this in more detail in this article.) With subwoofers, the settings also play a crucial role. Both the position itself and the woofer's controls must be adjusted with sensitivity and careful listening to correctly set the crossover frequency, level, and phase.
To position the woofer, first find a spot in the room that creates as little symmetry as possible with the surrounding walls. In many cases, this spot is about one-fifth of the room's length and width. Here, the distances to the walls are large and at the same time sufficiently different, so that the sound waves reflect as little as possible.
The crossover frequency determines above which frequency the sub's bass tones are no longer processed. This can be set both on the subwoofer itself and on the AV receiver. Normally, the crossover frequency is set to 80 Hz. Mini speakers usually require the frequency range above that, while floor-standing and compact speakers require the range below.
For level adjustment, it is advantageous to have a level meter or a corresponding smartphone app available. However, even without these aids, a listening test will be unavoidable, as it should be performed even after using tools – and with music that has plenty of bass. The more examples you use, the wider the bass range can be explored. Afterwards, the crossover frequency is fine-tuned. The rule here is: If the sub is no longer explicitly audible, but its sound is perceived as missing when it's turned off, you have ideally set it.
Finally, the phase makes everything a bit more coherent. Since it is rather subtle, its adjustment is done last. It describes temporal differences between signals and the signal components of sound waves. This means that adjusting the phase is intended to correct the travel time of the sound waves. The phase can be most successfully adjusted from the ideal listening position. From there, typical bass frequencies are selected, and attempts are made to experiment by ear. For example, if you play a piece with a very deep voice, you can determine from the listening position at which setting the voice sounds most natural and full.
When everything fits, the time-correct behavior is also important, because high tones travel faster through the air than low ones. Here, too, the listening position makes the decisive difference, because the phase setting, in particular, refers to a specific sweet spot. The goal is for the subwoofer waves to arrive at the ideal listening position in phase, meaning at the same time. The bass should sound full, powerful, and above all, deep. If that is the case, it is correctly adjusted. It combines punch with impeccable impulse fidelity and provides true listening pleasure.
Bowers & Wilkins DB3D
The British manufacturer Bowers & Wilkins has developed new, space-saving active subwoofers that are impressive to listen to. The design is sophisticated, the materials are high-quality, and the technical side has also been developed with foresight. The series consists of three models, with the 25 kg DB3D being the smallest of the devices. It stands out for its precise depth. Whether high-gloss black, red walnut, or satin white – the woofer is very flexible and integrates into any speaker system.
There are no controls on the back, as the DB3D is set up using the free configuration app. This saves users a lot of work. The app is available for Android and iOS-based devices and helps with both room positioning and the adjustment of audio and output presets. The integrated Room-EQ system allows for room correction without additional software or microphones.
In addition, the amplifier module, including cooling fins and connections, is located on the underside of the housing. The DB3D has two XLR, RCA, and 12V trigger connections each, as well as a 9-pin D-Sub RS-232 input. The model stands on appropriate feet, and this design solution makes the device particularly suitable for placement in living rooms. As is known from the popular 800 Series Diamond, the DB3D also features lightweight and ultra-stiff Aerofoil diaphragms. Since the electronics are located on the underside, these can work back-to-back to minimize cabinet vibrations. Thus, the baffles enable a clean, controlled bass sound. The amplifier power is a considerable 1000 watts, which is why the use of a correspondingly sophisticated amplifier is necessary.
Once the woofer is in operation, it provides deep and crisp bass. Even with high crossover frequencies, it blends excellently with the mid-range of small speakers. The compact DB3D impresses with its precise and clean contours and also offers excellent impulse fidelity.
SVS SB-2000
As one would expect from the loudspeaker and subwoofer manufacturer SVS, the SB-2000 naturally convinces with its enormous bass power, high level stability, and robust construction, rightfully making it one of the long-term favorites in the woofer sector. The active subwoofer weighs almost 16 kg, has a black MDF cabinet in ash or piano finishes, rounded corners, and a metal grille. The 12-inch drivers have a cast aluminum basket and radiate forward, perfectly complementing the model's modern look.
Great emphasis was placed on the internal values of the compact woofer. Thus, the voice coil is particularly powerful due to its extensive dimensioning, while the centering spider ensures acoustic linearity. A long-throw rubber surround ensures good durability and is, along with the centering spider, another flexible connection that connects the oscillating part and the basket. SVS also considered impulse fidelity, which is why the aluminum-polypropylene membrane is light and equally stiff.
Let's move on to the Class D amplifier. This delivers a continuous RMS power of 500 watts, and even up to 1100 watts for short periods, for example, to support an explosion in a film. Due to the Class D principle, little heat loss is produced during amplification, and the amplifier also consumes particularly little energy in standby mode.
The heart of the modern woofer is located at the back. Stereo RCA inputs and outputs, a continuously variable phase and volume control, and an adjustable crossover frequency have been placed on the rear. Below that is the power amplifier. In addition, the sub can be looped in as a crossover between the preamplifier and power amplifier.
The pure bass power of the SB-2000 speaks for itself and goes hand in hand with excellent level stability. The contours are precisely audible, and the sub offers convincing impulse fidelity. Thus, the active subwoofer delivers on its promise: music and film sounds are reproduced without restriction, full and powerful.
Conclusion
Hi-Fi enthusiasts can learn a thing or two from home cinema fans, as they have long known that subwoofers can be an ideal complement. When properly set up, they blend harmoniously into the overall sound. The DB3D ideally fits into the stylish design of Bowers & Wilkins products and can be perfectly combined with the new 706 S2, for example. Furthermore, it is pioneering in terms of craftsmanship, mechanical design, and electronics. The powerful SB-2000, in turn, is solid and offers precision and impulse fidelity in addition to its timeless design.
Update 05.12.2017:
In this video, created during our home cinema re-opening, Raphael Vogt explains the basics of subwoofers:
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