The Striking Master & Dynamic MH40 Sealed Around-Ear Headphone

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Master & Dynamic MH40 ($399)
"My goodness, what a striking headphone," was my first thought laying eyes on the sealed, around-ear, Master & Dynamic MH40. My impressions remained quite similar during my first listening tests. Now, with many months experience, I can say with surety, "striking" is an excellent descriptor.

Let's start with the look of these cans...which is for me a strike right down the middle of my modern-day geek sensibilities. Real leather, real metal, stitching and texture, utilitarian yet sumptuous, old school in a contemporary way—design is a weird thing so I don't know why, but these really do it for me. I have the brown and silver version, but the cans also come in an all black, black and gunmetal, and some limited edition colors in partnership with Proenza Schouler. Personally, I would have gone with the black and gunmetal.

The look of the MH40 is clearly designed to show off its functionality as a headphone, and quite satisfyingly the construction appears to be as sturdy and useful as its design promises. The headband is a double stainless steel band and wire channel padded and covered with leather and held together at either end with a cast aluminum end cap. Headband pad is a tad thin but its memory foam and suple lambskin leather do a good job of spreading pressure nicely at the top of your head if you bend the headband around a bit to conform to the top of your head. The outer headband leather is a nicely grained cowhide.

Ear capsules are attached to the headband with a post and bail mechanism. Size adjustment is accomplished as the upper posts slide through a guide in the headband end caps. Guide tension is good and headphones remain securely in adjustment during use.

The upper and lower part of the post have a rotating joint allowing the headphone ear pieces to be rotated flat for storage and transport. This rotational movement is a little rough but functional. The earpieces can also tilt up and down in their bails; some spring tension is in this movement tending to return the ear pieces to a position parallel to the post. The reason I mention these two movements is that they aren't particularly precise or smooth, which leads to a condition where final adjustment on the head has to be done manually with a bit of fidgeting. A very minor issue.


The ear capsules themselves appear to be of solid aluminum, with headband-matching cowhide and grill with logo as design features. The right earpiece has a push button to mute the audio. Cable entries are available at the bottom of both ear pieces. There is a aluminum grill cover plate under the magnetically attached ear pads that protects the driver. This plate is held in place with with four screws having a very unusual three-pronged slot requiring a special tool to disassemble so I was unable to have a closer look at the MH40 innards.

Ear pads are lambskin covered and have a fairly tall opening (63mm) but not a particularly wide one (38mm). As a point of comparison, the Focal Spirit Professional (45mm x 38mm) and original Sennheiser Momentum (48m x 34mm) are consider widely as somewhat too small; the Shure SRH 1540 (63mm x 43mm) is quite roomy. The MH40 encircled my slightly smaller than average sized male ears completely without crowding, though my ear did touch the sides gently. The ear cushions were also fairly deep, and though my ear did barely touch the bottom there were no ridges or corners to irritate during long listening sessions.

Two cables are included with the MH40: a 56" with separate 3-button remote and mic; and a plain 79" cable. Both cables are claimed to be oxygen-free, but no percentage is published. The cables are fabric covered and nicely terminated with aluminum housed 3.5mm connectors. Other accessories include: a small cylindrical leather box for the spare cable; an M&D branded 1/8"-1/4" adapter; a fairly sturdy but not hard sided canvas carry bag; and packaging that doubles as a home storage case.


A Couple of Problems
Let's start with the small problem. The cable exits directly out of the bottom of the MH40 headphones using a straight connector. I connect mine to the left ear piece. When wearing a t-shirt and tipping my head to the left a good amount, the body of the connector will poke into my left shoulder. This, in and of itself, isn't really a problem, but it does force the fabric coated wire to rub against my shoulder quite often, and some mechanically born noise does travel up to the headphones. The case worsens if I'm wearing a coat and walking outside, where this noise of the cable rubbing against the collar and hood can be quite audible. I really would have preferred the connector be angled forward some when exiting the headphones.

The larger problem—one that make the first problem worse than it ought be—is that the MH40 is a headphone with a very tightly sealed front chamber. By that I mean the chamber between the ear and driver/baffle plate enclosed by the ear pad is tightly sealed. While this kind of "pressure chamber" headphone was the norm many years ago (Beyer DT48 being the archetypal example), todays headphones tend to shy away from this type of design for a number of reasons.

First, if a headphone is able to make a very tightly sealed enclosure on the side of your head, it will also be able to not make a tight seal when there's hair or glasses arms in the way. The performance of a headphone like this will vary strongly depending on the quality of the seal. With a headphone of this type, one often feels the need to fidget with the headphones to get them to seal and sound best, and I found this to be the case with the MH40. Most contemporary sealed headphones will have controlled leaks so that the inadvertently changing seal against the head contributes less to acoustical changes. But, these designed leaks also tend to reduce bass response; striking a tidy balance is very difficult.

Another problem with headphones of this type is that they tend to amplify mechanically born sound of the headphones and head. As I mentioned before, I do tend to get "microphonic" cable noise with these headphones due to the position of the connector, but it is elevated to the point it sometimes interferes with listening because the very sealed nature of these cans amplifies the mechanical noise more than most headphones would. I also find when watching movies in bed I will sometimes make little snoring noises even though I'm not asleep; these noises become clearly audible with the MH40. Similarly, chewing noise, my heartbeat, talking, or humming in these headphones can be louder than in most headphones.

This type of headphone will also, when pressed inward against the head, create a significant amount of pressure against the driver diaphragm itself, and cause it to momentarily deform in shape causing a "crinkling" noise. Most diaphragms will pop back into shape quickly, but sometime permanent wrinkles can appear in the diaphragm flexure patterns (the intentional pattern of folds and ridges in the diaphragm that help it to move as designed). I don't know to what degree the MH40 might be prone to problems like this, but I'd be careful with the MH40 not to press it too rapidly against the head, or against the table when the cushions are flat.

Despite all this talk about a strong acoustic seal, the MH40 provides only moderate amounts of isolation from outside noise. Similarly, sound leakage from the headphones is moderate. I think this happens because the strong seal provides a good mechanism to convert mechanical vibration of the headphone by outside sound into sound heard at the ear. More on this in the measurements section.

Bottom line: the Master & Dynamic MH40 will sometimes need a bit of fidgeting to achieve and keep a seal, and may be a bit bothersome at times with mechanical noise. The thing is, the sound of the MH40, likely due in part to its highly sealed pressure chamber, is intensely and very pleasingly punchy and dynamic. So much so, and so uniquely so, that it's probably worth living with the few oddities of a headphone of this type if it delivers on the sonic possibilities.

Now, let's talk about that sound....

Master & Dynamic