SUNFIRE XTEQ 8 SUBWOOFER
SUBWOOFER
It’s so small that you’ll be able to enjoy deep bass while still enjoying domestic harmony. Sunfire has thrown all its technology at one of its smallest subwoofers… and to good effect.
Many audiophiles, for reasons of domestic harmony, are obliged to listen to smaller loudspeakers than they’d like, which means that although they can usually enjoy superb midrange and treble, they miss out partially—or almost completely—on deep bass. Those same audiophiles, again for reasons of domestic harmony, are also unable to add a large subwoofer in order to deliver that bass.
If this sounds like your situation, help is at hand, because for US manufacturer Sunfire has come to the rescue with its XTEQ 8 subwoofer, which is so tiny that you’ll be able to sneak it into the room under your jumper, install it by hiding it from sight under a chair or behind your equipment rack and then simultaneously rejoice in the sudden addition of deep bass to your music and the continuance of domestic harmony.
THE EQUIPMENT
Sunfire is able to claim an amplifier power rating of 1,800 watts for the tiny XTEQ 8 subwoofer—far more power than would be possible if it used a conventional ClassAB amplifier—and quite possibly, even a Class-D amplifier—because it uses an unusual tracking down-converter amplifier developed by the famous US designer Bob Carver, who founded Sunfire.
But why would you want a 1,800-watt amplifier inside a subwoofer? The answer to that is partly physics and partly marketing. In order to extract good low-frequency extension, low distortion, and high volume levels from a subwoofer, you need a large enclosure. The problem is that very few consumers want large enclosures in their living spaces. So manufacturers build enclosures that are smaller than optimum, and whenever they do this, they have to compromise by making a choice between reducing low-frequency extension, increasing distortion, or lowering maximum volume levels: in other words, ‘something’s gotta give!’
However, there is a ‘work-around’ to getting bass out of a small cabinet, and it’s one that hinges around the fact that one reason the volume drops off when a cone is mounted in a small enclosure is that the amplifier has to work harder to push that cone, which requires more power… lots more power. In the past, it was not practical to include a sufficiently high-powered amplifier in small subwoofers—they simply cost too much to build. But Carver’s tracking down-converter amplifier was the first one to break the rules: it could deliver enormous amounts of power
very cost-effectively, and it was this that enabled Sunfire to build such small subwoofers… and this new Sunfire XTEQ 8 is certainly small… indeed at just 267×315×270mm (HWD) it’s the smallest model in the XTEQ range. (There are two larger models, the XTEQ 10 and XTEQ 12.)
As with all products Sunfire builds, the model numbers of the XTEQ 8 actually mean something. The ‘XT’ stands for eXtended Throw, because the roll-surrounds fitted to the drivers in these models have Sunfire’s so-called ‘Asymmetrical Cardioid Surround’ geometry, which the company says: ‘ enables them to travel over a very long throw without distorting.’ The ‘EQ’ stands for Equalisation, except that in this case, the equalisation is automated. Each subwoofer comes with its own microphone and has a signal generator and measurement circuitry built in that can be used to measure the output of the subwoofer in your room, after which it can then automatically adjust the frequency response of the subwoofer for best performance in that room. It does this at four frequencies: 35Hz, 49Hz, 64Hz and 84Hz. (And if, for any reason, you don’t like the result of the automated circuitry, you can over-ride it, and instead set the equalisation ‘by ear’.)
There have been several improvements to Sunfire’s automatic equalisation circuitry over the years it’s been available, the most significant of which is to my mind that this latest iteration is by far the easiest and the fastest to use. However, another significant improvement was the switch from analogue to digital circuitry, which made the calibrations and equalisation more precise.
As for the final number in the model name—the ‘8’—that’s good ol’ imperial inches, showing that the XTEQ 8 has an 8-inch (203mm) diameter bass driver. And yes, that’s driver singular… there is only the one driver, and it’s on the left side of the subwoofer as you’re looking at it from the front. The circular thing that looks like a driver on the opposite side to the woofer (that is, on the right side of the subwoofer as you’re looking at it from the front) is actually a passive radiator—that is, although it has a cone and suspension, it does not have a voice coil or a magnet: its motion comes about entirely in response to air pressure variations inside the cabinet caused by the movement of the other side-firing bass driver: which is the reason some people call passive radiators ‘drone cones’. (They’re also known as auxiliary bass radiators, or ABRs). Whatever you decide to call them, Sunfire is at least honest enough to point out that it is a passive radiator: Some manufacturers don’t mention it at all, presumably hoping you’ll think you’re getting multiple drivers.
The rear panel of the Sunfire XTEQ 8 has both unbalanced (via RCA) and balanced (via XLR) inputs as well as two line-level outputs. The line-level outputs can be a simple pass-through (unaffected by any of the subwoofer’s settings) or high-passed through an 85Hz high-pass filter, using a switch located between the left and right output terminals. There’s also ‘Slave Input’ and ‘Slave Output’ terminals, which allow you to link multiple XTEQ 8 subwoofers together. By using the ‘Slave’ links to do this, all the settings you make on the ‘Master’ subwoofer will be replicated on the ‘Slave’ subwoofers, which greatly simpli- fies operation if you are using two or more subwoofers. Using dual subwoofers is a classic way to solve issues you may have with room modes, plus it’s also an easy, efficient, and cost-effective way of increasing bass levels in larger rooms.
A rotary control is used to adjust crossover frequency, and is adjustable from 30Hz to 100Hz, plus there’s a ‘Bypass’ setting at the extreme clockwise setting of the control. The phase control—also rotary—is continuously adjustable between 0° and 180°. The level control is rotary, with calibration markings only for ‘Min’, ‘0dB’ and ‘Max’. There are several fittings for use with the automatic equalisation circuitry, including an EQ LED, a ‘Start’ button, an EQ on/off switch and a microphone input. The other controls are a 12V d.c. trigger for remote power switching, a power LED and a mains power switch. Although the mains power switch has only two positions (off and on) the XTEQ 8 is fitted with a signal-sensing circuit that will turn the subwoofer off after a period of time during which it does not detect an audio signal. If you then apply an audio signal, it will switch on automatically. (I prefer three-position power switches—Off, On, Auto—but for no particular reason… it’s just an idiosyncratic personal preference.)
IN USE AND PERFORMANCE
When it comes to getting the ultimate performance from a subwoofer it is essential that
The circuit will automatically adjust the frequency response of the subwoofer for the best performance in your room