Earlier this year, I reviewed PSB’s M4U 2 active noise-cancelling headphone ($399.99)—the firm’s first-ever headphone product. Candidly, I was very impressed by the M4U 2, not only because of the absolute levels of performance it delivered, which was quite high, but also and more specifically because of how well rounded and well thought-out the whole package was.  The draw, as I observed in my review, is that the M4U 2 is in a sense a “headphone for all seasons”—a headphone that offers all the convenience and noise-cancelling features listeners might want, but that can just as easily be configured to provide sonic purity for the purists. What is more, the headphone incorporates voicing insights that PSB founder Paul Barton has developed over a lifetime of loudspeaker design work. 

There really is so much to like about the M4U 2 (“M4U”, by the way, stands for “music for you”) that one might reasonably ask why PSB would need to release any other model. Yet now we have a sibling to the M4U 2, called the M4U 1, which is a passive headphone that sells for $100 less. I thought it might be useful to ask what market the M4U 1 is meant to serve and what its comparative advantages or disadvantages might be vis-à-vis the M4U 2.

Unboxing: What’s in the Box?

Packaging for the M4U 1 is closely patterned after that for the M4U 2, which is to say that it’s gorgeous and very appealing. Within the main carton are a fold-open pair of boxes, one contain a tray for the product manual and most of the headphone’s accessories and the other containing a tray that holds the headphones themselves (packed inside a semi-hard-shell case), plus a few more accessories. Once you get everything spread out on a table, here’s what you’ll find:

• One set of M4U 1 headphones.
• A matching semi-hard-shell case with zipper closure.
• One spare set of headphone ear pads.
• A flight or “airline” adaptor.
• A 1/8-inch to ¼-inch adaptor.
• A cleaning cloth.
• Two 1.5m signal cords—one with an iPhone/Blackberry-compatible inline remote and mic module, the other without.
• A minimalist and mostly graphical user’s guide.

Key Features Worth Knowing About

As you might expect, the M4U 1 share a number of design features in common with it more costly big brother, the M4U 2. But for those of you who are perhaps not familiar with the M4U 2, let me give you a brief list of highlights.

• The M4U 1 is a purely passive (that is, non-self-powered) headphone that features 40mm dynamic drivers.
• The headphone frame is sturdy, flexible, and made of polycarbonate. By design, the headphone frame folds to allow the ‘phones to fit in their compact carrying case.
• The headphone ear cups (or driver housings, if you will) are very sturdy and made of an ABS + polycarbonate material. Importantly, the ear cups are “Gyro suspended”, which is PSB-speak for a system that allows the ear cups to swivel up and down, and from side-to-side. You might think all headphones would be designed this way in the interest of comfort, but surprisingly many are not, so that we’re very glad that PSB has “done the right thing” with its design.
• A very cool and distinctive feature is that the M4U 1 features detachable signal cables and—please note—offers the capability for the cable to plug in to either the left or right ear cups of the M4U 1 (at the user’s option, of course). This cool touch means that the ‘phones can work comfortable with desktop audio systems where your electronics might need to be positioned on either the left or right hand side of the desk. Clever, no?
• Voicing: A truly big deal is that the M4U 1—like the M4U 2—is voiced for what PSB terms “room feel.” In practice, this means the frequency response curve of the M4U 1 is voiced to mimic the sound of a high quality loudspeaker as heard in a typical room environment (not an anechoic lab). Loudspeakers benefit from a certain amount of low frequency “room gain”, so that designer Paul Barton gave his headphone a touch of bass-lift that mimics that room gain. Barton, by the way, would point out that this is really important, given that the overwhelming majority of records are mastered for speaker-based systems—not for headphones. This is precisely the sort of insight that a veteran designer of Barton’s stature can bring to the party.
• An iPhone/Blackberry compatible signal cable with an inline remote/mic module means the M4U 1 can be used as a headset for smartphone users.
• A simpler straight-line signal cable with no remote/mic module may appeal to purists who prefer to keep their signal paths as simple as possible.

M4U 1 and M4U 2 Compared 

From 10 feet away, it would be hard to tell any difference between the M4U 1 and M4U 2, but when considered up close here’s how their differences stack up.

Points in Favour of the M4U 2

• Versatility: The M4U 2 is very versatile, offering three modes of operation: passive, active, or active with noise cancellation. All three modes can be used with either a straight-line signal cable or with a smartphone compatible cable.
• Sound Quality: The M4U 2 sounds very good in passive mode, but even better with its onboard amp engaged.
• Switch Selectable Active Noise Cancellation: Unlike many competitors, the M4U 2 uses an analog—not digital—active noise cancellation system that is very effective and that does not seriously mar sound quality. But, a big key to the M4U 2’s appeal is that it gives you the option of turning the onboard amplifier on, but with the noise-cancellation system switched off. This enables the M4U 2 to appeal to purists in ways that most noise-cancellers cannot.

Points In Favour of the M4U 1

• Simplicity: The M4U 1 is pretty much a plug’n’play device for those who own outboard headphone amplifiers or would like to drive the ‘phones directly from an iDevice or smartphone. There are no batteries to install or replace, and no switch setting to memorize. Just plug the M4U 1 in and start listening; that’s all there is to it.
• Lower Price: The M4U 1 is priced $100 below the M4U 2, yet shares fundamentally the same design “DNA”.
• Lighter Weight: Although it’s almost impossible to tell from the specifications sheets, the M4U 1 is just slightly lighter than the M4U 2 (because it has no batteries and no onboard amplifier/noise cancellation module).
• The Appeal of Passive Designs: Some headphone enthusiasts strongly favor the use of high quality outboard headphone amplifiers (either portable or desktop models) and would staunchly argue that this approach almost always yields the best overall sound quality. For those in the outboard-amp camp, a passive headphone makes the most sense, since those users would perhaps be reluctant to use the onboard amplifier in the M4U 2.

How does the M4U 1 sound?

I need to get more listening time with the M4U 1 before I supply answers to this one, but suffice it to say that it sounds similar to an M4U 2 being operated in passive mode. I plan to do some careful back-and-forth comparisons between the passive M4U2 and the M4U 1 and I hope to present my findings in a full-length review later on. Until then, just know that the M4U 1 offers much (though of course not all) of the design DNA of the M4U 2 at an even more manageable price, while maintaining the exact same levels of quality, fit, finish, and all-around ingenuity that we prized so highly in the M4U 2.