Fact. The DB1D is the most powerful active subwoofer B&W has ever made. And if that fact doesn’t get your blood racing, how about that it has a low-frequency response that stretches down below 9Hz, as well as the ability to comfortably generate a sound pressure level of 92dBSPL across the pass band with negligible distortion?
Equipment
If you know something about subwoofers, you’re probably wondering how B&W manages high SPLs, low distortion and extended low-frequency performance simultaneously, since the three are usually mutually exclusive, as in if you optimise any two, you can’t expect the third.
When you see a DB1D in the flesh, and read the spec sheet, you’ll immediately know how B&W managed it. First, the cabinet is not exactly small! (It’s not exactly large, either, but it’s probably rather larger than you might have imagined.) In fact, the cabinet is exactly 460 by 429 by 410mm (HWD). Second—and you really can’t tell this from the photographs, the bass driver is a full 300mm in diameter, which is ‘way bigger than the drivers fitted to most subwoofers. Moreover, although you can only see one bass driver in most of the photographs, the B&W DB1D has TWO bass drivers (the second one also being 300mm in diameter). The Thiele/Small diameter for each cone is 250mm, which gives a total cone area of 981cm².
At this point, you’re probably thinking to yourself: ‘So what? Lots of subwoofers have two drivers.’ And if you’re thinking that, I have to tell you that you’re wrong. Although many subwoofers ‘appear’ to have two bass drivers, often only one of those two is a real driver—one with a voice coil, a magnet and all the trimmings. The other so-called ‘driver’ is actually a passive radiator, or ‘drone cone’, which does not have a voice coil, or a magnet—and sometimes not even a spider suspension. It’s just a cone. How could such a driver work? When the active driver’s cone moves ‘backwards’ into the cabinet, it compresses the air inside the cabinet, which in turn drives the cone of the passive driver outwards. When the active driver’s cone moves ‘outwards’ it rarefies the air inside the cabinet, which causes the air pressure in the room to force the passive driver’s cone back inside the cabinet. It’s this oscillating movement of the passive cone that creates sound.
Obviously, using a passive radiator is ‘way cheaper than providing a second driver but more importantly it also works completely differently, performing an entirely different function to an active driver. A passive radiator does not increase the overall sound pressure level, or the subwoofer’s power handling ability. It just provides some additional output over a very limited range of low frequencies, but in so doing, it ‘sucks’ some power from the main driver, which is then only able to deliver reduced output at those frequencies… so it’s a case of swings and roundabouts.
So why do some subwoofer manufacturers use one driven cone and one passive radiator? Frankly, one reason is that they’re hoping that many buyers will think they’re getting two drivers, and thus getting more ‘bang for their buck’.
The other reason is rather too technical to go into in the limited amount of space I have available for this review, but fitting a passive radiator means the manufacturer can make the cabinet a bit smaller than it would otherwise have to be, which makes the subwoofer a more attractive sales proposition, since most buyers prefer small subwoofers.
Providing two bass drivers, as B&W has with the DB1D, means twice the power handling capability, a 3dB increase in sound pressure level, minimal cabinet vibration due to the ‘equal but opposite’ action of the cones, which effectively cancels vibrations, reduced distortion (because the voice coils operate in the most linear region of the magnetic field) and a greatly increased ‘grip’ on the air in the room, due to the increase in the cone area. To get the same cone area from a single driver would require that single cone to be 40cm in diameter.
As for the cones in the drivers in the DB1D, they’re made from a brand-new material B&W originally developed for its flagship 800 Series Diamond loudspeaker. The construction of the cone is very similar to that originally used for B&W’s ‘Rohacell’ cones, which sandwiched a foam core between two skins of woven carbon-fibre however, unlike the ‘Rohacell’ driver, whose foam core is the same thickness everywhere across the cone, the core in this new ‘Aerofoil’ cone is not constant over the cone’s diameter, but varies depending on the distance from the point at which it attaches to the voice coil former. The curve is not dissimilar to the curve of an aircraft wing, which is no doubt the reason B&W calls the new driver an ‘Aerofoil’ driver. B&W says of these aerofoil cones: ‘these light, ultra-stiff drivers resist bending and flexing far longer than conventional cones, delivering controlled bass with outstanding precision.’
If you’ve been following my description so far, you will have realised that in the DB1D, because the polarity of the cones is the same, both cones move outwards at the same time, and also inwards at the same time (a complementary motion B&W describes in its literature as being ‘balanced’.) This means that each driver is working in the opposite direction to the other, and thus working ‘against’ each other, which requires the amplifier driving them to work very hard indeed. Or it would have to work hard if it were not sufficiently powerful to be able to manage this task with ease, and since the amplifier B&W is using inside the DB1D is rated with a power output of 2,000-watts, I’d be the first to say that it was sufficiently powerful to accomplish this ‘with ease.’
To deliver this kind of power, B&W is using a Hypex Class-D amplifier designed by Bruno Putzeys, who is sometimes called the modern ‘father’ of Class-D design. (Class-D amplifiers have been around since before Putzeys was born, but he was the first to produce efficient, cost-effective designs suitable for use in consumer electronics components.) I wasn’t prepared to pry open the DB1D’s cabinet to check the type of Hypex module that’s being used, so it’s a total guess that it’s a Hypex UCD2K, and a further (and possibly even wilder) guess that it’s driven by a 3KA700 switch-mode power supply (which is also made by Hypex).
If you’ve been looking at the photos of the B&W DB1D that accompany this review you should have noticed something quite strange. It has no controls—no volume control, no crossover frequency control, no phase control… in fact none of the controls you’d usually find on a powered subwoofer. ‘Ah!’ you say, having noticed that RS-232 port, ‘it’s controlled from your computer, like B&W’s earlier DB Series subwoofers.’ Well, no, that’s not true… you cannot control the DB1D using your computer (Actually, you can, but that RS232 interface only enables the DB1D to be incorporated into a remote control home automation system).
No, the reason there are no controls (and no remote control either, for that matter) is that B&W has gone all ‘appy’ and the DB1B is now controlled via Bluetooth using a phone or tablet, with the B&W ‘DB Subwoofers’ app, available for iOS or Android, but you must be running iOS Version 10 (or later) or Android Version 5 (or later). This app gives you control over volume, crossover frequency, phase, plus the slope of the high-pass filter (12dB/octave or 24dB/octave).
But B&W’s ‘DB Subwoofers’ app does much, much more than this. By using the microphone in your device, and test tones built into the subwoofer, it can equalise the frequency response of the subwoofer to deliver a flat frequency response at your listening position, almost irrespective of where you position the subwoofer, or the size and shape of your listening room.
Once you’ve equalised the response, you can then choose to listen to the equalised response, a ‘flat’ response, or a response that you’ve tailored to suit your personal preference, using the 5-band equaliser built into the B&W DB1B.
Despite being powerful, I don’t think the app is particularly well-designed. Firstly, it’s certainly not intuitive. You’re really going to have to download the manual to get a grip on what’s going on. Perhaps my biggest issue is that it doesn’t show the choices you’re able to make. Here’s an example: When the AUTO ON display shows < Enabled > you can’t see the three choices you have for this option, which are ‘High Sensitivity’, ‘Low Sensitivity’ and ‘Disabled’. Here’s another: Where the screen shows INPUTS you can only see a choice between XLR and RCA. Hidden behind this façade are Stereo, LFE and Disabled Choices, and layered beneath these are Input Gain adjustments (–10dB to +10dB) and layered beneath these, the manual EQ functions. I also don’t think the control layering hierarchy is logical… but that could just be me. Remember though, that I didn’t have the luxury of having the DB1D’s features demonstrated to me by a hi-fi dealer in the same manner that a normal consumer would be, so I was starting from scratch. Luckily, I had B&W’s excellent Owner’s Manual in front of me to help out, in which you’ll find pictures of all of the ‘screens’ of the app, and where they’re located.
The DB1D loaned to me for this review by Bowers & Wilkins Australia was flawlessly finished in a superb piano black lacquer. Your other options are a white piano lacquer or a real wood Rosenut veneer. No matter what colour you choose, the cloth on the two grilles will be black.
Automatic room equalisation
The provision of automatic room equalisation makes the B&W DB1D far less sensitive to room placement than if the EQ were not fitted, but sensible room positioning will minimise the need for equalisation and result in better overall performance. The process for determining this is fairly simple, but the explanation of how to do it fairly lengthy, so you’d be best advised to read the article at which will explain how to go about it. However, when you end up with your list of suggested positions, you should disregard any where one of the two drivers in the DB1D would be close to a rear or side wall. Also, use only positions that are forward or off to one side of the listening position, not behind it. And if one or more of the suggested positions is in the same plane as the left and right speakers, prefer this position over all the others.
Once you have determined the best room position, you then use the automatic equalisation calibration system built into the DB1D which is controlled by the app. I ran into a problem here, because the calibration system didn’t work with my Android phone. This is due, according to B&W to ‘microphone incompatibilities’. A list of phones that don’t have ‘microphone incompatibilities’ can be found on B&W’s website. Luckily my better half uses an iPhone, so I loaded the DB Subwoofer app onto that and in a few more moments we were away!
B&W’s calibration system allows you to optimise the DB1D’s frequency response for the prime listening position only (the ‘sweet spot’), for a ‘couch’ (two or three listeners sitting alongside each other) or for an ‘average’ that ensures the low frequencies will be ‘averaged’ over the entire room. But the first thing you have to do is ‘calibrate’ your phone’s microphone, which you do by placing the phone very close to the cone of one of the DB1D’s two bass drivers (it doesn’t matter which one). This is a ‘near-field’ test that allows the app’s circuitry to generate a correction file to compensate for the phone microphone’s frequency response.
After then selecting your preferred calibration technique you press ‘Next’ after which the DB1D generates a series of test tones, during which you position your phone at the positions advised on your phone’s screen by the app. I was rather surprised to find these test tones were sine sweeps (repeated over and over if you’re testing multiple positions) rather than band-limited pink noise, which I would have thought was far more suitable for low-frequency testing (sine waves are particularly susceptible to room modes), but I guess B&W’s engineers know what they’re doing.
Once the calibration is complete, pressing ‘Next’ takes you to a final screen on the app which advises the frequencies at which the DB1D has applied compensation. Unlike some subwoofers where you have to use the calibrated setting, the B&W DB Subwoofer app allows you to switch between a calibrated setting and an uncalibrated one. You can also create your own ‘DIY’ frequency response by manually adjusting the DB1D’s equaliser. If you decide to do this, I would recommend putting a real-time spectrum analyser app on your phone, playing pink noise through the DB1D, then adjusting the equaliser for the flattest response. There’s plenty of room for adjustment, since the equaliser has centre frequencies at 20Hz, 28Hz, 40Hz, 56Hz and 80Hz, each one of which is adjustable over a 15dB range (–10dB to +5dB).
Of course it’s not only about matching the DB1D’s response to the acoustics of your room, you also have to match the high-frequency roll-off the subwoofer to the low-frequency roll-off of your main speakers. If your main speakers are made by B&W this will be super-easy, because the low-frequency roll-offs of all current (and quite a few older) B&W models are already pre-programmed into the DB Subwoofer app. If you’re not using B&W speakers, you have to choose the ‘Other Speaker’ setting, which then opens a dialogue that lets you choose select the low pass frequency anywhere between 25Hz and 150Hz (or Off if you’re connecting the DB1D to an LFE output), the crossover slope (12dB/octave or 24dB/octave, as noted previously) and the phase (0°, 90°, 180°, or 270°).
