Expert review and test of the GoldenEar SuperSub X Subwoofer by Australian Hi-Fi Magazine. Free pdf download included.

Have you ever had a subwoofer attack you? Well, by ‘attack’ I actually mean ‘move menacingly towards you.’ I have. It was a bit scary. What was happening was that the drivers in the subwoofer were generating so much force that the cabinet was vibrating more in one direction than the other, which caused the cabinet to move towards me… or at least it did until I turned the volume down, which stopped it in its tracks.

GoldenEar is obviously aware of this phenomenon and has taken two steps to avoid it happening with its newest subwoofer, the SuperSub X, which also happens to be the smallest and lightest subwoofer in its ‘SuperSub’ series… and so would be—theoretically at least—the most likely to move of its own accord.

The Equipment

The first design approach involves actively preventing any unwanted driver movement from causing the cabinet to move. In the SuperSub X this is achieved by mounting the two active drivers on either side of the cabinet, so that any unwanted motional forces they create are equal and opposite… and, as all erudite readers of this august journal would be aware, Isaac Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction, so that two forces that are equal and opposite each other will cancel each other out. GoldenEar has left nothing to chance, however, so it’s also fitted four extremely compliant flexible rubber feet to the SuperSub X. These not only absorb any remaining unwanted motion, but also keep the down-firing passive radiator the correct distance from the floor so its output will properly contribute to the soundfield.

The active drivers inside the GoldenEar SuperSub X have circular cones made of strong, thick, paper pulp, with large paper pulp dustcaps. The mounting hole diameter of each driver is 205mm but the effective diameter of each cone is 165mm. There are two other ‘drivers’ inside the SuperSub X, but they’re passive radiators, lacking voice-coils and magnets, and are therefore driven not by your amplifier’s electrical power, but by the air pressure differences inside the cabinet caused by the movement of the two active drivers.

The two passive radiators (GoldenEar calls these units ‘quadratic planar infrasonic radiators’) are rectangular-ish in shape with a long side of 220mm and a short side of 190mm. Like the powered drivers, the passive radiators are mounted on opposite ‘sides’ of the cabinet, but this time the ‘sides’ are in fact the top and bottom of the cabinet, with one driver facing upwards and the other facing downwards.

The upwards-facing driver is protected by a black metal perforated mesh grille (as are the side-firing active drivers) but the down-facing driver is grille-free.

Using passive radiators to harness the otherwise wasted energy from the rear of the driven cones is a very sensible approach that enables higher sound pressure levels to be generated than would otherwise be the case, and extends the low-frequency response further downwards than would otherwise be possible. According to GoldenEar’s Sandy Gross, using passive radiators (rather than a bass reflex port) enables the SuperSub X to, in the company’s words, ‘perform like a well-tuned transmission line but with superior transient performance and control.’

We like that it enables the cabinet to be sealed, which means that common small household pests (cockroaches, mice… even possums!) will be unable to use the warm, cosy interior of the subwoofer as a home (as they have been known to do with bass reflex enclosures). The amplifier inside the SuperSub X is a Class-D design rated by GoldenEar as having a power output of 1,400-watts. Again, according to Sandy Gross, its circuit design is based on circuitry that was originally developed for GoldenEar’s Triton One powered loudspeakers (where the low-frequency section of the speaker is powered, but the midrange and high-frequency sections are passive). I know that many audiophiles have it in for Class-D designs and, when we’re talking about wideband amplification, particularly at high frequencies, I agree that Class D has its peculiarities. But there’s absolutely no reason not to use a Class-D amplifier in a subwoofer, because it’s never going to be called on to deliver any high frequencies and the load it has to drive is known, so the Class-D circuit can be optimised for it. So in fact, a subwoofer designer would be insane not to use a Class-D amplifier… plus, of course, an SMPS to supply it with voltage and current.

You should not be surprised to learn that the controls for the SuperSub X are on the rear panel, because it’s the only surface they could be on—except for the front panel of course, and you wouldn’t want to destroy that beautiful expanse of piano-black gloss paint, would you? The essential volume and crossover frequency are rotary controls with a very smooth, silky action and a rather gorgeous shape. Why settle for circular control knobs when you can have ones like this? The crossover frequency control enables adjustment from 40Hz to 150Hz, with a single midway calibration point at 95Hz.

There are only two inputs—left-channel and right-channel—both via gold-plated RCA connectors. If you’re using an LFE output from your amplifier or receiver, it should be plugged into the left-channel input. A switch alongside the crossover frequency control lets you switch between left/right in and LFE in. Alongside this switch is a chameleon LED that indicates power status. It’s marked both ‘Auto’ and ‘On/Off’ but you have no other control over the delivery of power to the SuperSub X, because there is neither a mains power switch, nor a secondary one: Once you have plugged in the power cord, the SuperSub X automatically powers up, after which you have only the options of using the ‘Auto’ mode, so that when it detects an audio signal at one or the other of its inputs, it will switch itself on and then stay on until it has not detected any type of audio signal for around 20 minutes, after which it will switch to standby mode, or the ‘On’ mode, in which it stays on all the time.

So the only way of ensuring the SuperSub X is truly ‘off’ is by switching the mains power off at the 240V wall socket. Also missing is any type of phase switch—either a two position (0/180°) toggle switch or a rotary (0–180°) control. This will very slightly restrict your ability to correctly tune the SuperSub X to integrate perfectly with your main speakers, but it’s not a deal-breaker.

The GoldenEar SuperSub X measures 325×356×335mm and weighs 14.1kg. It comes with a five-year warranty on the drivers and passive radiators, and a three-year warranty on the electronics.

 

In Use and Performance

The low-frequency nature of the sound produced by subwoofers means that they will always work best when placed in one of only a few specific locations in your listening room. GoldenEar’s Owner’s Manual has some appropriate advice about this, but you’d be best-advised to use a rather more scientific method of establishing where you should put the SuperSub X in your listening room. That method is too lengthy to detail in this review, but you can read about it here: www.tinyurl.com/subwoofer-placement. (Just to make it clear, the best position in a room for a subwoofer is the best for every subwoofer, so you only have to determine the best specific location the once. If you later decide to upgrade your subwoofer, it would go in the same position.)

After you have correctly positioned your subwoofer, you need to adjust the output level and crossover frequency to ensure correct integration with your main speakers. (And if, for aesthetic or other reasons you’ve chosen a non-optimal position in your room for the subwoofer, this fine-tuning will be even more essential.) Again, GoldenEar’s Owner’s Manual has appropriate advice about this, but there is really no substitute for using test equipment to do it. Luckily, the only ‘test equipment’ you will need is your mobile phone, a low-cost app for it and an equally low-cost CD. The calibration process is very simple but, like the positioning procedure, too lengthy to outline in this review, so you can read how to do it here: www.tinyurl.com/subwoofer-calibration

As has been pointed out on these pages many times, size does matter when it comes to subwoofers. All other things being equal (and here I’m talking about the on-board amplifier power and the sophistication of the DSP circuitry on-board) it’s the subwoofer with the largest driver (or drivers) and the largest cabinet that will produce the highest undistorted sound pressure levels at the lowest frequencies. That said, the development of high-power Class-D amplifiers and the easy availability of DSP processing has meant that the performance of modern ‘small-cabinet’ subwoofers such as the SuperSub X can easily match—or exceed—the performance of large subwoofers from the last century that lacked these refinements. You do have to pay the piper of course, because high-power Class-D amplifiers, digital signal processing and specialised stiff-suspension low-frequency drivers (and passive radiators) don’t come cheap. That old drag racing aphorism comes to mind: ‘The only thing that goes faster than cubic inches is rectangular dollars.’

One of my go-to discs when I first fire up any subwoofer is the DVD of Gaspar Noé’s truly awful film from 2002, ‘Irreversible’. It’s so awful that it is reported that many cinema-goers walked out at its premiere. The reason for the walkout might certainly have been the subject matter but it might also have been that for about the first 30 minutes of the film Noé mixed into the soundtrack a low-frequency (28Hz) sine wave signal at low level. While producers often add low-frequency sounds to their movies to induce a sense of foreboding, it’s claimed that Noé added this particular sound only to try to drive people from the theatre in order to drum up publicity for it. I can report that the SuperSub X had absolutely no problem reproducing this low frequency attention-getter… though the frequency is so low that many people won’t hear it at all, whilst others will hear it without realising it’s on the soundtrack, and not caused by nearby traffic.

I then played the relevant sections of other movies I have purchased for the low frequencies on their soundtracks (why else would anyone own the ‘Jurassic’ movies, and most particularly ‘Jurassic World’, whose plot is so full of holes the genetically-modified dinosaur whose escape causes all the mayhem could have escaped through any one of them. Still, given the number of mistakes in the movie, why should I be surprised?). Through-out, the GoldenEar SuperSub X proved itself to be a solid performer, producing low-frequency sound effects so accurately you really could imagine that that’s the sound a body makes when it hits the ground, or when a truck crashes into a tree. The sound of thunder was particularly well-reproduced. I found that I achieved the most realistic results when I maintained the subwoofer’s volume at appropriately realistic levels, so that the low frequency volume was correctly balanced with the overall volume of the movie. I’ve heard many systems where the subwoofer volume has been amped-up to unrealistic levels, presumably in an attempt to make the sound more exciting. You should always resist this temptation for aesthetic reasons, but with the SuperSub X, you’ll need to do it not only for reasons of aesthetics, but also because it tends to lose a little focus if it’s worked too hard.

Switching to musical fare took a lot of pressure off the SuperSub X, because unless you’re heavily into pipe organ works, most music does not actually dig too deeply into the lowest musical octave, which extends from 20Hz to 40Hz. (Any search for deep bass in an audio system should keep in mind that the lowest ‘C’ on a piano—which on most pianos is only three notes shy of being the lowest key on the keyboard—is a frequency of 32.6Hz and that the lowest note on a four-string electric bass guitar (‘E’) has a frequency of 41.2Hz. The tuned pitch of a kick drum varies depending on the ‘sound’ the drummer prefers, but it’s rarely below 40Hz and mostly up around 50Hz—though a kick drum does have lots of energy above and below its tuned frequency).

I found the SuperSub X to be a very musical subwoofer, delivering correctly pitched and timed bass no matter what musical fare I played. However its performance certainly varies depending on how much you’re asking it to do. It’s at its best when partnered with large, three-way floor-standing speakers, where it adds substantial extra impact and depth to the deepest bass notes, and is able to do this fast and fluidly while still delivering high volume levels. If, on the other hand, you partner it with small, two-way bookshelf loudspeakers, the sound is still fast and fluid, and you’ll hear all the wonderful bass sound you’ve been missing by owning only a pair of two-way speakers (because with such speakers you will be missing out on both the deep bass and the not-so-deep bass), but with this type of pairing you’ll have to keep a weather eye on the volume levels, because if you ask too much of the SuperSub X by turning the volume too high, the clarity of the lowest bass will fall off, and rhythm and pace will become less defined.

As with all subwoofers, the idea is that you turn the level up until you can hear the contribution from the subwoofer, then turn it back down slightly, until you can’t. It sounds counter-intuitive, but it works!

Conclusion

Whether you’re looking for a subwoofer for a home theatre system, or one for a two-channel system, and whether you have large speakers or small, GoldenEar’s SuperSub X will deliver the deep bass you’re missing out on.  # Rob Giles

Laboratory Test Results

Newport Test Labs measured the frequency response of the GoldenEar SuperSub X when its crossover was set to maximum as being 30Hz to 150Hz ±3dB. When the crossover is set to minimum, Newport Test Labs measured the frequency response as being 22Hz to 120Hz ±3dB. The frequency response when the LFE input is used was exactly the same as that when the crossover control was set to maximum: 30Hz to 150Hz ±3dB. None of the measured responses marries up with GoldenEar’s specification of 12Hz to 250Hz, but GoldenEar’s specification doesn’t state any dB envelope. As you can see from Graph 1, the GoldenEar SuperSub X certainly produces output at 12Hz and at 250Hz, but at 12Hz the output is down 20dB, and at 250Hz it’s down 25dB!

Graph 1 shows that if you set the crossover frequency to 150Hz, the SuperSub X’s output will be at its most linear over the range 40Hz to 130Hz, where it’s approximately ±3dB, which is an excellent result. If you set the crossover frequency to 40Hz, the SuperSub X will be the most linear over the range 25Hz to 80Hz… again an excellent result. This means if you pair the SuperSub X with a pair of bookshelf speakers and use the maximum crossover setting, you’ll handily extend response almost flat all the way down to 40Hz, and if you pair the SuperSub X with a large pair of floor-standers and use the minimum setting of the crossover control, you’ll equally handily extend the response almost flat down to 25Hz.



Graph 3 shows the nearfield responses of the bass driver(s) and passive radiator(s). You can see that the passive radiators’ maximum output occurs at 25Hz, rolling off very steeply below this frequency, as you’d expect. Above this frequency the passive radiators still produce significant output up to around 80Hz, and there’s some interaction between them at the drivers visible as a slight trough around 43Hz and a slight peak at around 55Hz. As for the drivers, you can see the response below about 30Hz is the same no matter what setting of the crossover frequency control you use. Above that, the passive radiators also exert some influence on the response of the drivers themselves, more so at lower settings of the crossover frequency control, but the response of the bass drivers is still remarkably linear, particularly at the 150Hz setting of the crossover.

Overall, excellent performance from such a small powered subwoofer. # Steve Holding

POSTCRIPT: In order to use any main speakers in conjunction with the GoldenEar SuperSub X you will need to ensure correct integration of the subwoofer's output with that of the main speakers by setting the subwoofer's volume, phase and crossover frequency controls correctly. You can read an article on a simple, effective method of how to do that HERE