Australian HIFI - - ON TEST -

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 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

Us­ing pas­sive ra­di­a­tors to har­ness the oth­er­wise wasted en­ergy from the rear of the driven cones is very sen­si­ble

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