PSB Speakers M4U 2 Active Noise-Cancelling Headphone (Playback 59)

PSB Speakers M4U 2 Active Noise-Cancelling Headphone (Playback 59)

The famous Canadian firm PSB Speakers is the latest entrant in a growing group of speaker makers who have decided to enter the headphone marketplace, in this case with the introduction of the M4U 2 active noise-cancelling headphone ($400). But while PSB is not the first speaker maker to take up the headphone gauntlet, they may be one of the first to turn a designer of company founder Paul Barton’s formidable talents loose on an all-new, clean-sheet-of-paper design—and that make a concerted effort to put music first.

From the outset, the M4U 2 provides all the right features likely to make the product a commercial success. First, it is a noise-canceller, meaning that it steps into a proven, popular product category (just ask Bose). Second, it is—like all noise cancellers—a self-powered headphone, meaning that unlike many of today’s most ambitious $400 headphones it needs no outboard amplifier to sound its best. Third, it is set up to serve both as a headphone and as a headset because—for many thousands of listeners--smartphones have become the musical source components of choice. Fourth, the M4U 2 pays attention to all the little details so many competitors overlook: details such as ergonomics, beautiful industrial design, self-evident build quality, and exquisite packaging. But even with all these plusses going for it, we think the biggest plus of all is the M4U 2’s sound quality.

Here’s the deal; everything Mr. Barton has learned through decades of PSB speaker design has been poured directly into the M4U 2, and his experience makes a difference you can readily hear. As with his speaker designs, Barton has designed the M4U 2 so that it not only measures well in empirical lab tests, but also sounds good, as verified through carefully controlled listening tests. Barton has also leveraged his speaker-making expertise by deliberately voicing the M4U 2 to provide what PSB terms an “in-room” feel. In practice this means the M4U 2 response curve closely matches the in-room response characteristics of PSB loudspeakers—complete with a certain amount of low-frequency “room gain”, just as loudspeakers enjoy. Since most records are geared for playback through loudspeakers. Barton reasoned that it only made sense to give the M4U 2 a similar degree of bass lift. 

Going further, Barton also took an active role in creating the M4U 2’s amplifier/noise-cancelling system, striving to make it effective at blocking noise, yet also capable of preserving musical details and subtleties. Finally, Barton gave the M4U 2 a feature that, to our knowledge, no other noise cancelling headphone provides: namely, the ability to power up the headphone’s amplifier section without engaging the DSP-driven noise-cancellation circuitry, a step that reduces measured distortion considerably. Again this is a feature audio purists can easily hear and appreciate.

This review will address several different aspects of the M4U 2, including its design, ergonomic qualities, convenience features, and most importantly, its sound.


Basic Design, PSB M4U 2

•40mm PSB-designed dynamic driver in a closed-back headphone.
•Built-in amplifier/noise cancellation circuitry powered by dual AAA batteries battery life is approximately 55 hours). Surprisingly, the M4U 2 uses what PSB terms a “low noise linear amplifier”—not a class D amplifier as found in many competing designs.
•Noise-Cancellation System: Unlike some competing noise-cancelling headphones, the M4U 2 uses an analog—not a DSP-driven—noise cancellation system that uses four built-in microphones to detect room noise, rather than the usual two mics. PSB comments that, “We found that there was more accurate noise measurement collection using four microphones instead of the usual two-microphone set up, which yielded better cancellation across a wider bandwidth when used with our low noise linear amplifier.”
•Tri-Mode design. The M4U 2 provides three distinct operating modes:

oPassive mode: The M4U 2 can easily be driven by iPods, iPhones and the like, even when battery power is switched off.
oActive mode: The M4U 2’s amplifier is turned on, but noise-cancellation circuitry is not engaged.
oActive Noise-Cancelling mode: Both the M4U 2’s amplifier and noise cancellation circuitry are turned on.

•Headphone voicing is said to provide an “in-room feel,” meaning that the tonal balance of the M4U 2 closely approximates the sound you would hear from high performance speakers in a typical listening room (complete with the “room gain” most loudspeakers enjoy).
•Distinctive Stereo Monitor function: Both signal cables provide an in-line switch labeled “M” to denote the Stereo Monitor function. Here’s how the function works relative to the M4U 2’s three operating modes.

oPassive Mode: Pressing the “M” button has no effect.
oActive Mode: Pressing the “M” button suspends music playback so that the listener can hear external room sounds.
oActive Noise-Cancelling Mode: Pressing the “M” button suspends music playback and uses the noise cancellation system to amplify room sounds.

• Headband frame is made of Polycarbonate and is adjustable via “click fittings.” The frame is collapsible to all the headphones to fit in a relatively compact travel case.
•Ear cups (or as PSB calls them, “Driver enclosures”) are made of ABS plus Polycarbonate.
•Both the headband frame and ear cups feature comfortable, Leatherette-covered pads.
•Comfort Fit Gyro-Suspended Ear Cups/Pads: The M4U 2 ear cup mounting system allows ear cups to swivel vertically and laterally for an optimal fit.
•Detachable, user-replaceable 1.2.-meter signal cables—one configured for monitoring applications and the other for headset capabilities. The headset cable provides a built in mic/remote module compatible with iPhones and Blackberry phones.
•Dual signal cable inputs: The M4U2 allows users to plug the headphone’s stereo signal cable into either the left or right-side ear cup, according to their preference.



•Spare set of Leatherette-covered ear pads.
•Airline adapter.
•3.5mm mini-jack plug to 6.3mm phone jack plug adapter.
•Two 1.2-meter signal cables with 3.5mm mini-jack plugs on the headphone side.

o“Monitoring” cable, targeted primarily toward audio purists, also provides a 3-conductor 3.5mm mini-jack plug for connecting to personal digital music players, tablets, etc.
oHeadset or “remote/mic” cable, targeted toward smartphone users, features a 4-conductor 3.5mm mini-jack plug compatible with iPhones and Blackberry phones.
oBoth cables feature the room monitor function switches as mentioned above.

•Cleaning cloth.
•Zipper closure carrying case made of molded EVA.


Let me come right out and say it; PSB’s M4U 2 is hands down the best sounding noise-cancelling headphone I’ve yet heard, and it is the only one that invites side-by-side comparison with today’s best passive $400 headphones, which is saying a mouthful. This statement implies several things.

First, the voicing curve of the M4U 2 is wonderfully smooth, evenly and accurately balanced, and blessed with a judicious touch of bass lift that, as advertised, does convey the sense of hearing a fine loudspeaker in a real-world listening room, complete with “room gain.” Not long ago, I had the privilege of meeting with PSB’s Paul Barton and a small group of journalists for a guided tour of Canada’s National Research Council (NRC) acoustics labs—the very facility where PSB’s speakers and where the M4U 2 headphone went through performance verification tests. During the tour, I had the opportunity to participate in some blind listening tests in the NRC’s IEC-certified listening room, and thus to evaluate the sound of several PSB speakers, plus some competing models. Every time I plug in the M4U 2’s, I’m struck by how similar their voicing is to that of some of PSB’s top loudspeakers such as the Synchrony 1 or the new Imagine T2 floorstanders. If you know how good PSB’s top speakers are, then you’ll appreciate that this is high praise indeed.

Next, let me go further to argue that the M4U 2 can, in subtle but significant ways, outperform even the best of PSB’s speakers. I would say, for example, that the M4U 2 offers a more transparent, detailed, and open sound than most loudspeakers do—a sound that gives the headphone an effortlessly vibrant and engaging quality. I would also point out that the M4U 2’s offer deeply extended, powerful, and yet well-defined bass response, bass that few sensibly priced loudspeakers could ever hope to equal.

But one of the most important differentiators of all is that the M4U 2 is very easy to drive—both in passive and active modes—so that it provides vigorous, expansive dynamics without ever sounding like it is working hard. True, you can get dynamics this good from some speaker systems, but to do so you’ll need good, powerful (and often expensive) amplification and carefully picked speaker cables. But with the M4U 2, the amp and cables are already provided, making a true plug’n’play audiophile headphone.

Headphone aficionados often argue that open-back headphone designs often enjoy a small but worthwhile edge in terms of openness and transparency—a stereotype with which I might generally agree, but the M4U 2 seems for the most part to be an exception to the rule. It has none of the compressed, closed-in sound that some listeners associate with closed-back designs; on the contrary, it sounds unfettered and alive.

Are the M4U 2s fully the equal of today’s best roughly $400 passive headphones? I would say that, when push comes to shove, they do not, though the gap is amazingly narrow. Three great passive headphones that I think offer slightly higher performance than the M4U 2 would be the $395 Fischer Audio FA-002W High Edition (click to read the review), the $399 HiFiMAN HE-400 with Rev2 drivers (click to read the review), and the 399.99 (MAP) Shure SRH1440 (watch for Steven Stone’s upcoming Playback review). When backed by appropriately high-quality headphone amplifiers, each of these ‘phones can potentially offer a bit more midrange and treble detail, even more open and extended highs, and difficult to describe quality of heightened resolution and focus. But the tradeoff, please bear in mind, is that those competing ‘phones really need good outboard amps to work their full magic, whereas the M4U 2, which comes very close in overall performance, comes with its own amp already built-in and ready to travel. Add in the fact that the M4U 2 is a noise-canceller with headset capabilities, and you can easily see why the PSB headphone would likely be the go-to choice for pragmatic, real-world listeners (especially for those who find the idea of springing for an outboard headphone amp a little far-fetched in the first place).

Let me offer several more observations prospective M4U 2 customers might want to know about. First, unlike the overwhelming majority of noise-cancelling headphones I’ve tried, the M4U 2 offers a really sensitive and good-sounding passive mode that presents an easy-to drive 32 Ohm load to iPods and the like. Thus, should the batteries die and you don’t have a spare set handy, the passive mode is really very good and eminently listenable. Second, the M4U 2’s best sounding mode is without a doubt the Active Mode with noise-cancelling features turned off. Purists will find the M4U2 sounds, well, purer, more vibrant, detailed, and alive with the amp on than with it off. Interestingly, when the amp is turned off, the input impedance of the M4U 2 becomes a super easy-to-drive 10kOhms. The Active Noise Cancelling Mode sounds similar, but not identical, to the Active Mode, with bass and lower mids that are not quite a free flowing and expressive as when the noise-cancellation circuitry is disabled. According to published PSB specifications, distortion is somewhat higher with the Noise Cancellation turned on.

Noise reduction capabilities for the M4U 2 are very good, with no additive electronic noise from the noise-cancellation circuitry. Some noise-cancellers create a sonic “robbing Peter to pay Paul” scenario, where noise goes down in one part of the audio spectrum but seems to increase in other parts of the spectrum—a problem the M4U 2 simply does not have. I would say, though, that the noise reduction capabilities of the M4U 2, good though they may be, are not quite the equal of the unusually versatile and effective noise reduction circuits found in Audio-Technica’s superb new ATH-ANC9 noise-cancelling headphone. The tradeoff, though, is that the M4U 2 is unquestionably the more refined musical performer of the two, which we count as an important advantage in the PSB’s favor.

Caveats: Most of my reactions to the sound of the M4U 2s were very positive, though I do have a few minor nits to pick, most of which relate back to the fact that when powered up the M4U 2s have a lot of gain and are extremely sensitive. For the most part high gain and high sensitive are good things, but the one drawback is that any unintentional noise or hard, sharp transient sounds will be vigorously amplified right along with the music.

Thus, I found that when I first pressed the Stereo Monitor buttons on the M4U 2’s signal cables (with the power turned on), I heard a hard, intense “CLAAaack!” though the headphones. As near as I could tell these sharp transient noises didn’t do any real damage, but they scared the bejibbers out of me when they first occurred. Similarly, swiveling the M4U 2’s signal plugs within the output jacks of an iPod or iPhone occasionally induced surprisingly loud “ticks” or “pops” (possibly due to unseen dirt or grit in the jacks). I also discovered that, through the M4U 2, marginally noisy source components could suddenly start to sound annoyingly noisy. Any hum or sonic “hash” that’s present in the source will be reproduced through these ‘phones, loud and clear.


One way to get the measure of the M4U 2 is try it on the cover of the Rolling Stones’ “Under My Thumb” from saxophonist Tim Ries’ Stones World: The Rolling Stones Project, Vol. 2 [Sunny Side Records]. On this album, as on Ries’ earlier The Rolling Stones Project, the objective has been to provide wildly inventive and yet still quite recognizable jazz/world-music re-creations of popular Stones rock classics—old and well-loved songs made brand new again. For “Under My Thumb”, which was recorded in Puerto Rico, Ries tapped the talents of an all-star Latin jazz ensemble and the results are, through a capable headphone at any rate, simply breathtaking.

The song is driven forward by an intensely syncopated, very high energy Latin percussion section and electric bass guitar, with melodic lines supplied by a red-hot horn section and Ries’ sax, with the whole works capped off with snarky Latin vocals served up with just the right amount of Jagger-esque swagger. Right off the bat, you notice that lower frequency instruments have plenty of weight, depth and punch, yet are not even vaguely loose or sloppy-sounding. On the contrary, bass transient are—please pardon the pun—“tight as a drum” with tons of crackle and snap. The horn section in general, and Ries’ sax in particular, have excellent tonal purity and a lovely burnished glow, but what is particularly gripping is the sheer amount of “bite” and dynamic energy they provide—qualities the M4U 2 capture with impressive vividness and transparency. Finally, we come to the vocals, which are so jaunty and irreverent that seem almost to have the feel of Antonio Banderas channeling the spirit of Jagger himself. Again, the M4U 2’s do a great job retrieving each little inflection and point of emphasis, making the vocal lines sound much more lively and realistic. Can the M4U 2s do low-level details? Yes, they can as you’ll see if you listen to the very end of the track, where you’ll hear the now distant voice of the vocalist (who has stepped away from his mic) saying softly, but with palpable satisfaction and pride in the ensemble’s performance, “Yeah, man… …that’s what I’m talkin’ about.”

To get a better sense for what the M4U 2s could do, I put on one of my favorite orchestral test/demo tracks, the Sir Neville Mariner/Academy of St. Martin in the Fields performance of Gordon Getty’s “Plump Jack” Overture [Pentatone, SACD]. Though just a little over twelve minutes long, this composition manages to showcase most of the sections and many of the moods a full-scale symphony orchestra, making it a very useful vehicle for evaluating audio components of all kinds. Frankly, many headphones have proven less than satisfactory devices for reproducing the sounds of orchestras at play, either because they lack adequate subtlety, detail, tonal purity, dynamic clout, or some combination of the above. But happily, and impressively, the M4U 2 had no such problems, demonstrating a terrific ability to adapt to the requirements of the passages at hand. As heard through the PSBs, loud, low frequency percussion passages sent deep but clear waves of base energy into my ear canals, while seconds later lighter-hearted string and woodwind passage tapped the headphone’s openness and transparency to capture a more ethereal and delicate feel. Granted, some of today’s very best $400 passive headphone can, if fed by appropriately sophisticated source components and amps, eek out a slightly more open and revealing presentation overall. But among real-world headphones that don’t need outboard amps, etc., the M4U 2s offer an almost unprecedented combination of power, control, and openness. Few passive headphones, and no noise-cancelling headphones that we have yet heard, can match the M4U 2 in these respects.


Consider this noise-cancelling headphone if:

•You want what may well be the best-sounding noise-cancelling headphone on the planet—one that truly puts music first.
•You like the idea of a self-powered headphone that offers two Active modes, giving you the choice of engaging noise-cancellation or not.
•You want a headphone that offers the smooth, accurate, neutral voicing of a fine loudspeaker system and that makes a really credible attempt to re-create the kind of low-frequency room gain that loudspeakers enjoy.
•You want an active headphone whose passive mode actually sounds good and thus is more than an afterthought thrown in just in case the batteries fail.

Look further if:

•You are a purist and like to push sonic limits; a handful of passive headphones in this class may offer higher absolute performance limits, but note that to tap those performance capabilities you’ll likely need to spring for a costly, high performance outboard amp.

Ratings (relative to comparably priced noise-cancelling headphones):

•Tonal balance: 10
•Clarity: 10
•Dynamics: 9.5
•Comfort/Fit: 9.5
•Noise isolation/cancellation: 9
•Ease of Use: 9.5
•Value: 10


PSB’s M4U 2 is one of the most cleverly conceived, well executed, versatile, and good sounding headphones that $400 can possibly buy. It literally offers something for everyone: sufficient sound quality to please purists, cool-looking industrial design and great fit and finish for those who demand headphones that look as good as they sound, terrific comfort and ease of use for those who will spend long hours listening to their ‘phones, headset functionality for an ever-growing number of smartphone users, and effective noise-cancellation for those constantly on the go. This is why we call the M4U 2 a “headphone for all seasons.”

The M4U 2 is certainly not cheap, but it is arguably a bargain for what it is and does. Seriously, this could be as much headphone as many users might ever need or want. As we see it, the really impressive thing is that this is Paul Barton’s first-ever headphone design; it’s simply amazing to see how many things he got right on his very first try. Well done, Mr. Barton.


PSB Speaker M4U 2 Active Noise-Cancelling Headphone
Type: Circumaural (over-the-ear), closed-back headphone with active noise-cancelling capabilities.
Accessories: As listed under “FEATURES”, above.
Driver complement: 40mm dynamic driver in closed-back housing
Frequency response: 20 Hz – 20kHz, ± 1 ½ dB

Active Mode: 0.25%
Active Noise Cancelling Modes: 0.5%

Sensitivity: 102 dB

Passive Mode: 32 Ohms
Active & Active Noise Cancelling Modes: 10k Ohms

Weight: 12.8 oz.
Price: $400.00

Manufacturer Information
PSB Speakers International
(800) 263-4641 (Toll Free)

blog comments powered by Disqus

Featured Articles