Dynaudio’s Sub 6 Active DSP subwoofer is clever… very, very clever. It’s so clever that when it knows what main speakers you’re using it will automatically adjust its output level and crossover frequency and frequency response so that you get perfect, seamless sound from the depths of the subwoofer’s bass extremities to the extreme highs of your main speakers.

There is a catch though… a limit to its cleverness. Well, two catches really, a perfect Catch 22. It relies on you telling it which main speakers you are using, and on you being clever enough to make sure those main speakers are made by Dynaudio. But, given the proven, documented high quality of Dynaudio’s loudspeakers, and the number of main speakers in the company’s range, I can’t see either catch becoming a deal-breaker.

The Equipment
I don’t think I have ever been so fooled by the size of a subwoofer as I was when I unpacked the Dynaudio Sub 6. It’s tiny. Really tiny. Gee, I thought, it sure looked bigger in the pictures in the brochure. But if I was fooled by the size of the Sub 6, I was absolutely flummoxed by its weight. When I leaned over to pull it out of its box, it didn’t budge. Mmm, I thought, it must be stuck. After enlisting my significant other to hold the box down firmly, I tried again. No luck. I then enlisted the aid of the third human member of the household to give us both a hand. And out it came. So not ‘stuck’, just heavy… really heavy. ‘Way too heavy for its size. What is Dynaudio putting in this thing anyway? Lead?

It turned out that what Dynaudio is ‘putting in this thing’ are two absolutely massively-constructed 240mm diameter bass drivers, each with a gigantic ferrite magnet, plus a power amplifier to drive them that is rated with an output of 500-watts. Plus the cabinet is solid as too, because it has to constrain the enormous internal air pressures generated by the two bass drivers without falling apart at the seams.

Those two drivers are at opposite ends of the unusually-shaped (and sized) cabinet. I say ‘unusually’ because it’s far, far wider than it’s deep… or than it is high. For the record, it’s 470×333×268mm (WHD).

The reason for these odd dimensions is that the Dynaudio Sub 6 is designed to be operated close to a wall, so the two bass drivers get acoustic assist not only from the floor, but also from the wall.

As for there being two drivers, and them being on opposite sides of the cabinet, for those reasons, for the design, read on…

There are many reasons Dynaudio would have wanted to use two drivers rather than just one. Curiously enough, the most important one is not the one that immediately springs to mind, and it is that Dynaudio wanted to minimise cabinet vibration. You can use two drivers to do this by means of force-cancelling. If you use just a single driver in a subwoofer, Newton’s Third Law of Motion (‘For every action, there is an equal and opposite reaction’) means that every time the cone moves outwards, it will create an opposite force on the cabinet, and the same when the cone is moving inwards, and because there’s nothing to cancel those forces, they must be dissipated by the cabinet. When you use two drivers in a subwoofer, mounted opposite each other, the counteracting forces cancel each other out, so the cabinet is not required to do anything at all other than constrain the huge increase in internal air pressure when the cones move inwards, and the partial vacuum created when they move outwards.

Another reason is that using two drivers means that Dynaudio is moving more air thanks to the increased cone area, thus delivering louder sound into the room. Regarding which, although Dynaudio rates these drivers as having a diameter of 240mm, the actual overall diameter of the basket is 230mm and that of the cone alone is 150mm. The Thiele/Small diameter is 175mm, which gives an effective cone area (Sd) of 240cm², which means that if Dynaudio had elected to use just a single driver in the Sub 6 and wanted to move the same amount of air, that driver would have to have had an overall diameter of around 305mm.

Yet another reason for having two drivers is that by splitting the driving amplifier’s output between two drivers, the overall amplifier power can be much higher, so the 500-watt output of the amplifier becomes 250-watts per driver. And higher amplifier power translates to higher sound pressure levels.

The drivers in the Dynaudio Sub 6 were built specifically for subwoofer use by Dynaudio itself (the company is one of the few in the world that makes all its own drivers) and the cones are made from a combination of aluminium, paper, and the same Magnesium Silicate Polymer (MSP) material Dynaudio uses in the bass drivers it manufactures for use in its two-way and three-way loudspeakers. Incorporating aluminium and paper into the magnesium silicate polymer not only stiffens the cone, which makes it more effective at delivering frequencies below 20Hz, it also damps resonances over a much wider frequency range than would be possible otherwise.

The enclosure of the Dynaudio Sub 6 is totally sealed: There is no bass reflex port. This is good for two reasons. Firstly, you won’t have to worry about audible ‘chuffing’ sounds, which can sometimes occur at high volume levels, even with the best-designed bass reflex ports. Secondly, you also won’t have to worry about small beasties using the bass reflex port as the entrance to their nest. (Editor’s Note: Lawson is referring to the fact that here in Australia, it’s not unknown for small rodents to make their homes inside loudspeaker—and subwoofer—cabinets that have bass reflex ports. Indeed there’s been one case of a native brushtail possum taking up residence inside a speaker cabinet, and not only is a possum a marsupial, rather than a rodent, but it could hardly be classified as being ‘small’ either. Apparently, sound does not interrupt their sleep. And if you’re not Australian, you need to know that brushtail possums are nocturnal, semi-arboreal marsupials of the family Phalangeridae, that are renowned for the noises they make whilst mating.)

The rear of the Dynaudio Sub 6 is home to a digital display that is distinguished by having champagne-coloured writing over a blue background, which dims if you haven’t used it for more than 12 seconds. A bright green LED underneath this display glows to indicate the subwoofer is on. The digital display is used to indicate the status of the DSP (and other) circuitry inside the Sub 6, all of which can be adjusted via a rotary control (to the right of the display), which has a ‘turn to adjust’ / ‘push to select’ action… though it’s one that I found not to be particularly intuitive, though certainly it was obvious enough that I didn’t need to read the Owner’s Manual in order to be able to correctly set all the available menu options… of which there are many.
Those many menu options include adjusting the input sensitivity of the Sub 6 (to best-match your amplifier’s line-level output, but probably most usefully to match an AV processor’s LFE output voltage), accessing a three-band parametric equaliser (frequency, gain and Q are adjustable for each of the three bands), setting the delay time before the Sub 6’s auto-standby circuitry kicks in (which includes being able to tell it not to kick in at all), plus, of course, the usual low-pass crossover frequency settings, adjustable from 40Hz to 120Hz (including a Bypass mode for use with LFE outputs).

Rather confusingly, the crossover frequency and Bypass settings are hidden under a sub-menu item titled ‘Presets’ and further buried under the sixteen presets that ensure the Sub 6 will integrate perfectly with Dynaudio loudspeakers. On the software version I was supplied (which I was assured was up to date, but can always be updated via the ‘Service’ USB socket to the left of the display), there were presets for the Dynaudio Special 25, Special 40, Contour 20, Contour 30, Contour 60, Contour 1.4LE, Contour 3.4LE, Confidence C1, Confidence C2, Confidence C4, Evidence Platinum, Evidence Temptation, Evidence Master, Focus 20XD, Focus 30XD, and Focus 60XD.

If you don’t own a pair of Dynaudio speakers, you’ll find you have to scroll through all 16 settings before you come to the ‘Do-It-Yourself’ options, after which turning the rotary control increments a 24dB/octave low-pass filter in 5Hz increments from 40Hz to 80Hz, and then in 10Hz increments from 80Hz to 120Hz and at the very end adds in the ‘ByPass’ setting. This might sound like it makes setting a chore, but it’s something you’ll only ever need to do the once, so it’s not really an issue.

But that isn’t the end of the available Menu options! You can also program in the distance from the subwoofer to your listening position, from the left-channel speaker to your listening position and from the right-channel speaker to your listening position. I briefly wondered why you’d need to do this at all until I looked below the display and realised that the Sub 6 has left and right channel outputs as well as left and right channel inputs. So yes, the DSP processor inside the Dynaudio Sub 6 can certainly apply delays so that the sound from the left speaker, right speaker and subwoofer arrive at your listening position at exactly the same time, no matter where your speakers (and the sub) are positioned, but to do this you need to connect your speakers to the Dynaudio Sub 6’s own outputs. This will be easy if they’re active speakers and will mean you also need to add external power amplifiers if they’re not. If you decide to go either route, I would advise using the balanced inputs and outputs provided—rather than the unbalanced ones provided—due to the long cable runs that would likely be required. (The reason being that using unbalanced cable would likely add excessive noise to the audio signal.)

I was a bit put out that what seemed to be a warning label on the rear panel of the Dynaudio Sub 6 warned only those who could speak Danish, Finnish, Norwegian or Swedish. I was so miffed at being linguistically left out that I put ‘Apparaten skall anslutes till jordat uttag’ into Google Translate, which told me the rear-panel warning said: ‘The appliance must be connected to a grounded socket.’ This seemed to me an important-enough warning that it merited being provided in other than Nordic languages, but since my subwoofer came with a three-pin power cord (active, neutral and earth), so the ‘appliance’ would be grounded by default, I figured that maybe it wasn’t a necessary warning in Australia. (Do Nordic mains plugs only have active and neutral terminals? I don’t know.)

Dynaudio’s Sub 6 is available in two different finishes: gloss white and satin black. I was supplied with the gloss white version, which I thought looked great… except for the black fabric grilles that were also supplied. Initially, I thought that someone in Dynaudio’s packing department had made a mistake and included black grilles instead of white ones. But it turned out that Dynaudio doesn’t make white grilles for the Sub 6; only black ones. Bummer! If this is a major turn-off for you, it’s easy enough to strip off the black cloth from the grille frames and replace it with white cloth or, indeed, any other colour cloth of your choosing. (Confession, I say ‘easy’ but I’ve not done it personally: I get my crafty sister to do it for me, and she’s the one who tells me that it’s ‘easy’.)

In Use and Performance
My other half had been impressed by the Dynaudio Sub 6 from the minute it came out of the packaging (she being one of the three of us required to extricate it from said packaging). ‘Hey,’ she exclaimed, ‘it’s narrow enough to fit against the wall behind the couch.’ And sure enough, loathe as I was to admit it, the Sub 6 fitted behind the couch perfectly, and those side-firing bass drivers still had plenty of room to breathe. It thus became, to all intents and purposes, an ‘invisible’ subwoofer.

Invisible to the eye, maybe, but certainly not invisible to the ears! Despite its diminutive size, Dynaudio’s little Sub 6 really packed a wallop, even from behind the lounge! It certainly sounded ‘way bigger than I thought it would, no doubt partly because of the trick of using the wall to give the bass extension and volume a helping hand, but also no doubt because of that 500-watts of Class-D power on-board and the incredible excursive ability of the two bass drivers. The drivers may be relatively small in terms of diameter, but the extent to which they can move back and forth is amazing, and the energy any driver can deliver is a function of both its cone area and its excursion.

To my ears, the bass delivered by the Dynaudio Sub 6 was very deep, very powerful and very, very clean. It was also exceptionally fast. No matter what I played, I was left with no doubt at all that the Dynaudio Sub 6 could keep up the pace. Kick-drum sound was exactly synchronised with the sound of rim-shots, timpani were clock-work timed with the orchestra and the precision of the pitching was perfect. Listening to electric bass, the sound of plucked strings was stomach-impacting, and I could even hear the pitch change as the bass strings bent… no mean feat at such low frequencies.

Best attribute of all, there was none of that sense of ‘sonic slowness’ that can sometimes dog the deep bass from subwoofers that depend on bass reflex ports to augment their low-frequency output. Tonal quality was also excellent, such that I was always able to hear instantly whether I was listening to an electric bass or a double bass or to a real Fender Rhodes rather than just a Korg pretending to be one.

Given the Dynaudio Sub 6’s outstanding performance in my music-only listening sessions, I pretty much knew what to expect when I used it in a multi-channel home theatre setting, and all my highest expectations were met, because this is a subwoofer that can dig down below 20Hz to frequencies that are these days mostly the ambit of the Foley studios that create the fake background sound effects that make modern-day movie sound sound so real, whether it’s the rolling thunder of an impending storm, the sound of a rocket launcher or the foot-falls of a Tyrannosaurus Rex.

(Interesting Factoid: Foley studios and the people who work in them—Foley artists—take their name after Jack Foley [1891–1967], who pioneered the sound effect techniques used in filmmaking.)

The abilities of the Dynaudio Sub 6 are such that when using the Dynaudio Sub 6 in a home theatre system, its low-frequency performance—in terms of both extension and level—will enhance your enjoyment of whatever movie or sports event you are watching, irrespective of the low-frequency ability of your main front speakers.

Conclusion
The well-known phrase ‘good things come in small packages’ perfectly describes my opinion of Dynaudio’s Sub 6 and, in what could very well be a world first, that opinion is shared by my wife, so I expect that, since I have a birthday coming up, one could very shortly be entering my life.

But not a white one thanks dear… I prefer black. Lawson Short

 

Readers interested in a full technical appraisal of the performance of the Dynaudio Sub 6 Subwoofer should continue on and read the LABORATORY REPORT which can be seen on hte original magazine pages as PDFS - click the graphs shown right. Readers should note that the results mentioned in the report, tabulated in performance charts and/or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.