Expert review and test of the Dynaudio Sub 3 Subwoofer by Australian Hi-Fi Magazine. Free pdf download included.

Dynaudio’s brand-new Sub 3 replaces the identically-sized Sub 250 in this Danish company’s line of powered subwoofers. Given that the Sub 250 was such a popular model, I wondered why this model hadn’t just been upgraded and called a Sub 250 MkII or some similar name. It turns out that the Sub 3 came about because the company’s engineers were working on trying to develop a smaller and lower-priced version of the Dynaudio Sub 600. To do this required developing a completely new bass driver, which in turn required a much higher-powered amplifier that had been inside the Sub 250. In the end, the Sub 3 incorporated so much of the ‘DNA’ of the Sub 600 that it was decided that ‘Sub 3’ would be a better descriptor for the new design.

The Equipment

Photographs don’t really give a true picture of the size of the Dynaudio Sub 3. It’s tiny.

In fact, if it were any smaller, Dynaudio’s engineers could not possibly have shoe-horned the new driver into the cabinet, because the new driver is 240mm in diameter. Despite the cone looking like those used on previous Dynaudio designs, the cone of the Sub 3 is made from a new material from Dynaudio that combines the company’s MSP (Magnesium Silicate Polymer) with aluminium and paper in what Dynaudio calls an MSP+ Hybrid drive unit. This new driver was designed specifically for use in subwoofers, with the new material providing two kinds of resonance damping.

Despite the Sub 3 enclosure being only 275×267×325mm (HWD), the front baffle is 37mm thick—twice as thick as I’d expect—which has the effect of reducing the volume of air inside the cabinet even further than the small size would dictate, so the volume is around 18-litres. Needless to say, this means Dynaudio’s engineers had to use a sealed enclosure, rather than a ported one, and also increase the power of the amplifier in order to be able to drive the cone hard enough to compress and rarefy the air trapped inside the enclosure. Dynaudio rates the amplifier inside the Sub 3 as having a power output of 300-watts.

The amplifier plate on the rear of the Sub 3 is unusual. Yes, it has the usual volume and crossover controls (both rotary, without any setting indications), plus a two-position phase switch (0/180°), but there’s also a three-position slider switch labelled ‘SAT highpass’ with positions marked ‘Flat’, ‘60Hz’ and ‘80Hz’, plus inputs marked ‘Sub/Sat’, inputs marked LFE/Slave In, and outputs marked ‘SAT output’ and ‘Slave OUT.’ There’s also a two-position ‘Slave/Sat’ switch.

All of which suggested to me that Dynaudio has envisaged that the Sub 3 could be used in four different applications.

1: The obvious one, which is that it would simply be added to an existing system to deliver additional—and possibly more extended—bass, as a stand-alone item without any interaction with other components in the system, like any other subwoofer to augment the low-frequency output of the main loudspeakers. (That is, both the subwoofer and the main speakers will reproduce low frequencies.)

2: In a two-channel sub/sat system,

 sending the entire audio signal to the sub prior to amplification, then letting the Sub 3 take out the lowest frequencies for amplification and delivery, then passing only the high-frequencies on to an external amplifier to power the pair of satellite speakers—or, perhaps, to powered satellite speakers, thus avoiding using an amplifier entirely. (That is, only the subwoofer will deliver low frequencies, and not the main speakers.)

3: In a multi-channel home theatre system, in which case it could be connected using either the first or second methods.

4: As ‘Slave’ subwoofer in order to regularise the sound pressure levels in a listening room to remove the inevitable high- and low-pressure areas caused by the room’s dimensions (a.k.a. ‘room modes’).

In this last case, it should be directly connected to another Sub 3 subwoofer (or subwoofers).

Depending on how you want to use the Sub 3 will depend on what features and connections you use, so it’s hardly a surprise that the Owners’ Manual that tells you what everything does, how to connect it and how to use it is 44 pages in length. It also means that it should be hardly a surprise that there are mistakes in the manual, one of the most egregious being the advice (on page 18) that if you use the LFE input, ‘the signal should not already be processed by the processor/receiver’. This is incorrect. If you use the LFE input, the signal SHOULD have been pre-processed. (Hopefully this mistake will have been corrected by the time you read this review.) However, my advice would be that unless you’re going to use the simplest subwoofer set-up (set-up 1 in the previous list), you should ask your hi-fi dealer to install the Sub 3 in your system for you.

Some of the obvious but completely understandable omissions on the Sub 3’s list of features and facilities are balanced line-level inputs and outputs, and speaker-level inputs and outputs. In practise this means the electronics you’re using with the Sub 3 will need to have a line output available (pre-out or record-out) or a dedicated subwoofer (or LFE) output in order to allow connection. There are few components that would not be able to manage this, but since there are a few out there I feel obliged to mention it.

In Use and Listening Sessions

Given the quality of the driver, the power output of the amplifier, and the extensive features on the Sub 3, Dynaudio was always going to have to make some compromises in order for the subwoofer to sell at its recommended retail price. One of those is that the rotary volume and crossover frequency controls are not of the same standard as I’ve experienced with previous Dynaudio products, with the controls having a rather coarse ‘feel’ when they’re being rotated and on my sample, the edges of both knobs scraped on the amplifier plate for a portion of their rotation. Neither of these minor failings should be any cause for concern, since the controls will only have to be set at the time of installation, after which they’d remain in the same position until you move the Sub 3 to another room. Another economy is the provision of a two-position phase switch, rather than a rotary control, about which more in the following paragraph.

All subwoofers need to be correctly positioned in a room and have their controls carefully adjusted to provide optimum performance, and the Dynaudio Sub 3 is no different in this regard, though the fact that it is so small and does not have a bass reflex port will mean there will be far more positioning options available for it than would be the case if it were larger and had a port. However, because it has only a two-position phase switch, rather than a variable one, you will have to pay close attention to correct time alignment, and ensure that the subwoofer is the same distance from your listening position as your main front speakers (though it need not necessarily be in the same plane as them). However, if you’re using the Sub 3 with a home theatre receiver that has time alignment compensation built in, you’ll be freed from even this minor restriction.

That the subwoofer is positioned correctly in the room and the controls are adjusted in such a way as to ensure a seamless transition of sound from the subwoofer to your main speakers is so important that you should take the time and trouble to do both. Full instructions on where to position the Sub 3 can be found at www.tinyurl.com/subwoofer-placement, and full instructions on how to correctly set the phase, crossover and volume controls can be found at www.tinyurl.com/subwoofer-calibration.

I started off by listening to music using the Dynaudio Sub 3 in concert with a very large pair of floor-standing loudspeakers which already had excellent bass response (with the crossover control set to 50Hz). Why? Because despite what the manufacturers of large floor-standing loudspeakers put in their specification sheets, even large floor-standers have trouble reproducing audio signals in the 16Hz to 32Hz region, so a subwoofer can be used to add authority to this deepest audible octave. The Dynaudio Sub 3 acquitted itself marvellously well in this role, not least because the bass it delivered was ultra-fast, without even the suggestion of unwanted overhang. The Sub 3 certainly added extra depth to organ music, but it even added extra ‘body’ to piano. But if you do use the Sub 3 in such a role, you’ll need to keep the overall volume at ‘reasonable’ levels, because there’s only so much you can ask a small subwoofer to do.

Next I switched over to a fairly substantial pair of bookshelf loudspeakers and this time, rather than just ‘adding’ the Dynaudio Sub 3 as I had with the floor-standers (that is, not using the Dynaudio’s internal crossover), this time I wired the Sub 3 so that it was producing all the low bass, so the bookshelf speakers now had to handle only the upper portion of the audio spectrum. I started my sessions with the high-pass switch set to 60Hz, but the Sub 3 was so easily handling the bass that I changed the setting to 80Hz, so the Dynaudios were delivering even more of the bass. They rose to the occasion, despite now having to deliver high-impact, high-energy bass sound from such instruments as drums, bass guitars, double-bass… plus of course, keyboard instruments such as piano and synthesiser. Listening to Bruce Dunlap (guitar) and Dan Kolton (double-bass) playing Threedledum (from Stereophile Test CD3) the depth and tone of Kolton’s double-bass was reproduced beautifully. I was also enamoured of the way the Dynaudio Sub 3 delivered the electric bass and frenetic drumming on Haley Grace’s Running (from her album ‘Ghost of a Girl’). This proved to me that the Dynaudio Sub 3 is a very musical-sounding subwoofer, with very low distortion, and that the bass it delivers is as clean as a whistle, without any sonic ‘character’ of its own, so it will meld with all loudspeakers you match with it, irrespective of their brand.

My final foray with the Dynaudio Sub 3 was using it in a 5.1-channel home theatre set-up, substituting for the much larger subwoofer and much more expensive that usually occupies the real estate of my listening room floor, this time connected via the LFE input. At low listening levels the Sub 3 was totally impressive: I could very well have been listening to my own subwoofer (sob!). It was only when I really cranked up the volume and played movies with some seriously riotous and unmusical sound effects (foleyed rather than real, in most cases) that the Sub 3 again revealed slight limitations in exactly how loudly it can play. That said, my room is very large, and I was playing very loudly. In a typical home-theatre set-up in a normal-sized room, I think you’ll find the Sub 3 will easily be able to deliver far louder sound than you will ever need.

Conclusion

It’s a cruel trick of physics that the smaller a designer makes a subwoofer the more expensive the components inside it have to be, because you need a hugely powerful amplifier to compensate for the lack of volume inside the cabinet, and then a superbly-specified—and superbly robust—low-frequency driver to be able to deal with the motive forces generated by that amplifier. So Dynaudio is to be congratulated for delivering such a high-performance subwoofer in such a small cabinet at such a low price.

But when it comes to pricing, it isn’t only Dynaudio that’s delivering on this count, because the company’s Australian distributor is obviously also doing its bit: My googling showed that (adjusted for the exchange rate) the Australian RRP is actually lower than the discounted price for this model in the USA.

So whereas most Australian distributors merely aim for parity pricing with the US, BusiSoft is aiming even higher. Winner! # Stan Samuels

Readers interested in a full technical appraisal of the performance of the Dynaudio Sub 3 Subwoofer should continue on and read the LABORATORY REPORT published on the following pages. 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.

Laboratory Test Report

In Newport Test Labs’ laboratory tests,the Dynaudio Sub 3 proved to have a very flat, extended and linear frequency response when using the LFE input, and also when using the line input with the crossover control set to its maximum (150Hz) position.

Graph 1 shows three in-room responses from the Dynaudio Sub 3, all measured at a distance of three metres, using a pink noise input source. All traces are the averaged result of multiple measurements, and are unfiltered. The black trace shows the frequency response using the LFE input, and you can see that it extends from 22Hz to 400Hz ±3dB. This trace really shows the subwoofer’s maximum capability, which would never be used, since you’d normally feed a band-limited signal to the Dynaudio Sub 3 via its LFE input. You can see, however, that the Dynaudio Sub 3 is still very well-behaved, even when it’s reproducing frequencies it would not normally be expected to reproduce at all.

The red trace on Graph 1 shows the Dynaudio Sub 3’s frequency response when the crossover control is set to its maximum (150Hz) position. You can see that the trace extends from 22Hz to 240Hz ±3dB, the upper frequency of which is quite a bit higher than I would have expected from a 150Hz crossover setting. In fact the response is essentially flat out to 150Hz, after which it rolls off at around 12dB per octave.

The green trace on Graph 1 is the Dynaudio Sub 3’s frequency response when the crossover control is set to its minimum (50Hz) position. You can see that the trace extends from 17Hz to 90Hz ±3dB, so again the actual frequency response is quite a bit more extended than I would have predicted at this setting of the crossover frequency control.

Graph 2 shows the same traces as on Graph 1, but this time Newport Test Labs has used third-octave post-processing to smooth the traces to make the differences between the three responses across the region between 30Hz and 100Hz a little bit clearer. (The smoothing reduces the measurement accuracy at very low frequencies, so you should ignore the traces below 30Hz.)

The Dynaudio Sub 3 is a very well-designed subwoofer that delivered excellent performance in Newport Test Labs’ tests. #  Steve Holding

POSTCRIPT: In order to use any main speakers in conjunction with the Dynaudio Sub 3 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