Polk Audio DSW MicroPro 4000, Small but mighty

• Relatively compact and very attractive in its "piano black" finish, yet capable of pinning us to our seats when the soundtrack gets serious

• Price: €1,825

• Specialists' rating: 5

• Text: Josep ARMENGOL

Thirty-seven years ago (1972), three friends who had just graduated from the University of Maryland (United States), led by Matthew Polk, decided to embark on the adventure of building their own audio components, especially loudspeakers. Today, Polk Audio remains one of the leading companies in this sector and has achieved remarkable popularity worldwide, thanks to products that perform very well and offer excellent value for money.

Its specialty is undoubtedly home theater, and within this field its catalog includes several "families" of loudspeakers for the different positions in a multichannel system, and for every budget. Among its active bass speakers, or subwoofers, the range includes no fewer than ten models, counting the previously known PSW and DSW lines and the brand-new DSW Micro Pro range, which sits at the top and itself consists of four models, from smallest to largest the 1000, 2000, 3000 and 4000. The last of these, the "flagship" of Polk Audio's subwoofers, is the subject of our Lab this month.

WHAT IT'S LIKE

There was a time when a subwoofer was little more than a box best hidden from view so as not to spoil the look of our room, which usually doubles as the living room. But this has been changing, thanks in large part to "digital" amplifiers capable of several hundred or even thousands of watts, which make it possible to achieve good bass pressure levels even with compact drivers and enclosures. The new Polk Audio DSW Micro Pro models follow this trend; in fact, the two most basic models (1000 and 2000) are cubes barely 30 cm on a side (yes, just over a foot) capable, according to their specifications, of reaching down to no less than 22 Hz. So compact, and finished in a luxurious glossy black lacquer (the famous piano black), that to see one is to want one.

Our "4000" is not much bigger: also almost cubic, in this case it measures about 40 cm on a side, although we had better be careful when moving it because it tips the scales at almost 30 kg. On the front is the active driver, 12 inches in diameter, with a trim piece (also piano black) mounted on the central plug, while the rear panel carries the array of usual (and not so usual) subwoofer connections and controls. The cube rests on four long rubber feet (which can be swapped for spikes if the floor is carpeted) that keep it about three centimeters off the floor. This clearance is necessary (though, as we will see, sometimes not sufficient), since underneath is the passive radiator, which ingeniously is not circular but square, making use of practically the entire available surface (precisely 12 inches on a side, the diameter of the driver). Of course, the enclosure is sealed (no bass reflex) given the presence of that passive radiator. As is well known, this may somewhat limit bass capability (which the radiator makes up for) and sensitivity, but in return the frequency response will be more linear and the bass more agile and fast.

As for the rear panel, the usual controls are the crossover frequency selector (continuous, between 40 and 120 Hz), two buttons for raising or lowering the volume, a switch to select off/on/auto-on by sensor (it switches off after 15 minutes without a music signal), apart from the main power switch next to the IEC power inlet, and both high-level (speaker binding posts) and line-level connections (stereo RCA inputs and outputs, plus a lone RCA for the LFE channel of an AV processor). Less usual, a MIC input reveals one of this subwoofer's particularities: an automatic correction system that equalizes its response to adapt it to our room and placement. A large heat sink occupying almost half the rear surface reveals that, despite running in highly efficient Class D, the internal amplifier can comfortably exceed a kW of power.

In the box, in addition to the subwoofer itself, we find the measurement microphone for the Polk Room Optimizer system, as well as a lightweight remote control that offers many other functions apart from on/off or volume control: four phase options, several preset placement options (if we have not performed the automatic calibration), a night mode, and so on. Without a display (which would in any case be hard to read from a distance), it is the illumination of the manufacturer's logo on the front (in blue, naturally) that indicates the functions we select with the remote control, using a somewhat cryptic system that we quickly get used to. For example, for volume (from 0 to 40), if we are at 24 it will blink twice slowly and four times quickly. Very ingenious.

TEST

Installation could not be simpler: just find a spot in our room where this compact and attractive cube fits, although it is advisable to leave at least ten or more centimeters of free space around it. Incidentally, the driver's powerful magnet is not shielded, so it is best not to place it near a CRT TV, to avoid distorting its picture.

Once it is positioned and connected both to the mains and to our audio-video processor (LFE input), we connect the supplied microphone and place it at our listening position. A long press of the room button on the remote control starts a sequence of low-frequency sounds with which the system measures our room's response and resonances, and adjusts itself to avoid exciting the modes that can result in boomy, muddy bass.

I tested the subwoofer without this adjustment (if it has been done, just press reset on the remote) and with it, in two different positions in my room, and to my surprise (you may call me a cynic, but some of these systems have disappointed me in the past) the improvement is clearly noticeable, and in both cases (near two different walls) the system was able to correct the response properly. In the absence of a precise measurement (of little use in this case, since we have no information about what the system does and cannot adjust it), it is easy to hear: a jazz track with a hard-working double bass player was enough (I always have a Ray Brown album handy for this), and without correction some notes swallowed up the others, whereas with the correction applied the response was more linear, the track much more pleasant, and details that would otherwise have been masked could be heard.

In this preliminary phase of the test, I was also able to discover two virtues of this Polk Audio: its bass extension (not a single note was missing at the bottom) and its speed, since I could follow the brilliant musician's fingers even in the liveliest moments. And something no less important: this subwoofer is very quiet; only within a hand's breadth of the driver can a faint electrical hum be heard, and this is something very few can boast of (more or less pronounced humming is common). Bravo.

After these tests, expectations for this subwoofer's performance with movies were very high, and the truth is that it did not disappoint me. Whether in scenes full of explosions with plenty of low frequencies (U571), in passages from movies with lots of action and effects (The Mummy 3 at the Yeti monastery, or Hellboy 2 fighting the giant in the market), or simply in gripping moments of a thriller (Max Payne), thanks to this Polk Audio we were never short of an ounce of emotion or impact. When a subwoofer "works" as well as this one, home theater takes on a new dimension, and one wonders how those who still doubt the usefulness of these dedicated low-frequency speakers can live without one. Make no mistake: along with installing a big screen, this is the most noticeable change you can make to any system.

As for sheer bass extension, using a test tone disc I was able to verify that the impressions matched its actual capability. Down to 30 Hz the response is trouble-free; below that we start to lose reproduction capability down to 25 Hz, and below that there is hardly anything down to 10 Hz, the lowest tone on my disc. Although the brand states 16 Hz, from what I have tested, genuinely getting below 30 Hz in my room is a real achievement, and for me this result qualifies the Polk Audio "4000" as excellent, since very few soundtracks have effects below those frequencies.

The only "but" is that in effects-heavy scenes the available power may be excessive: despite its almost 30 kilos of mass, when the level of bass being emitted starts to get wild... it moves it! I checked that the rubber feet were properly tightened, but even so, this subwoofer's internal potential is so tremendous that we will have to devise some way of securing it. Those with carpet should definitely fit spikes to leave it literally nailed to the floor. If our floor is hard (as in my case), one solution may be to use a small rug (with a non-slip backing) and put the spikes on it, or to leave it on the rubber feet but load it with a fair amount of weight on top (books or magazines, perhaps), although it would be a shame to hide its beautiful glossy black surface that way.

CONCLUSION

I have always considered Polk Audio products to offer good value for money, but I perhaps suspected that this was due more to how low the second factor (price) was than to the weight of the first (quality). This DSW Micro Pro 4000, which is not exactly cheap although it offers a lot for what it costs, has convinced me otherwise. Since we are making confessions, I also admit that I have never had much faith in those recent-generation, compact subwoofers that nonetheless claim capabilities that defy the laws of physics. Well, this Polk Audio has freed me from that prejudice too, because I am well aware of what a subwoofer with a 12-inch driver and a larger, even much larger, volume than this compact 40 cm cube can do, and I assure you that here you will not miss extension or impact, and its speed rises to the occasion.

It is a little beast, though very easy to tame thanks to the remote control and the automatic correction system with microphone, and a very beautiful beast thanks to its compact size and gorgeous glossy black finish. Recommended.

Jorge Gómez Consuegra, Manager of Joytel.



Dear Josep:

We are grateful for your thorough article, in which you have highlighted the key features of this new series of Polk Audio subwoofers, essentially the self-equalization system and adaptation to the room acoustics. We live in times when consumer electronics offers us innovations and features that do not always bring a clear advantage for the user, and it is gratifying that, from time to time, we can say that a particular innovation gives us a more enjoyable experience, in this case a musical or cinematic one (which is what it is all about).

Thank you also for highlighting Polk Audio's traditional value for money, which reveals the manufacturer's honesty.

Polk Audio DSW MicroPro 4000, Small but mighty

Specifications

FREQUENCY RESPONSE 16-140 Hz. CROSSOVER adjustable between 40 and 120 Hz. AMPLIFIER Class D, 1,200W rated (2,400W peak). CONNECTIVITY Line inputs (stereo RCA) or speaker inputs (stereo binding posts). DIMENSIONS 390 x 430 x 420 mm. WEIGHT 28.1 kg. DISTRIBUTOR Joytel (914471036).

Price: €1,825