The Striking Master & Dynamic MH40 Sealed Around-Ear Headphone

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

Jazz Casual's picture

Wonder if the designer took any design cues from the legendary HP1000? I've always admired the beauty of its utilitarian design.

zobel's picture

Looks like they, like the Sennheiser Momentums, are too small for me. They both are very sensitive, with the Momentums a better balanced sound, more refined, and these, punchier but with build issues. The NAD VISO HP50 while sounding wonderful, are too small in the ear chamber for me also. The Focal cans are too small too.

I'm glad I found the Sennheiser HD 380 Pro. They fit on big heads, big ears, are comfortable for long periods, are sensitive, have good isolation, good build quality, replaceable cable with shorter aftermarket cables for cheap, a nice hard shell case that they fold into, and sound quality that is hard to better. They are accurate, smooth and flat across the whole audible frequency range, with good, tight, deep bass extension. The angled drivers improve imaging. I use them in my recording studio as monitors, and as all-around sealed cans for general purpose use. They are an improvement over the HD 280 Pro in both fit and sound. They don't choke up at high volume as do the Shure SRH 1540. They are better balanced in sound than the ATH-M50X, and more comfortable. They are the best value at just $107.56 at Amazon now. They deserve a spot on the wall of fame. For a lot of us with big heads and ears, they are about the only viable choice for sealed full sized cans.

ultrabike's picture

Had them for a short time. I liked them too :).

Beagle's picture

when wearing these...and wondered what a semi-open design would be like.

Long time listener's picture

Tyll's comment about a mix of flaws that yields an engaging listening experience applies equally to an in-ear model that was mentioned in the last monthly update column: the NHT Superbuds. Their bass is kind of loose, and their upper mids kind of recessed--but they create a huge, immersive space and have surprising presence in spite of their flaws. Hugely enjoyable. A review would be nice.

RPGWiZaRD's picture

These may fit my tastes, I like an engaging "up-front" sound like I'd be on the stage with the band sorta with a punchy slightly/medium emphasized but tight bass.

BarbecueGamer's picture

Tyll, I have a request. I would absolutely LOVE to see you review the Sennheiser Momentum 2.0.

Tyll Hertsens's picture
I've requested them. Not sure when they'll get here.
BarbecueGamer's picture

That's great! I'll definitely be looking forward to it. Thanks for the reply Tyll.

Erukian's picture

I agree with everything you've said. I picked up these headphones and can see how they'd be the perfect office companion. I've gotten quite a few compliments from coworkers asking what these are and they look retro and very cool, then I let them listen and they're blown away. Except those noisy fabric covered cables rubbing against my collar, I wanted to point out the plug hitting your shoulder is not a problem for a taller guy like me (6'2), or anyone with a longer neck, I get about 1-2" of clearance from where the fabric cable sleeve leaves the jack. I can see how replacing the cables with something else can significantly increase comfort and microphonic noise.

I happen to have a very large head, and these are too tight for me, especially at the top (posts fully extended), so for that reason they're going back because it's not something I can live with day to day (head pain from from discomfort after 30 mins of listening).

Can someone please suggest some headphones for large head/large ears, fun and exciting sound without sacrificing much fidelity? Audeze EL8? Momentum 2? Doesn't need to be open or closed, but I prefer around ear.

Thanks again,

TheAudioGuild's picture

To meet ASTM standards requires a minimum of 0.001% oxygen to meet any "oxygen free" qualification.

C10100 is readily available and must have a minimum of 0.0005% oxygen.

Of course the oxygen content has absolutely no relevance to audio cables. It's only relevant in industrial applications where the presence of oxygen in the copper can interact with other elements and cause problems.

TheAudioGuild's picture

Excuse me, replace minimum with maximum in my above post. Sorry. Was listening to America's Test Kitchen while I was writing.

Meelaad's picture

Great review Tyll! You mentioned several times in this review that this is a very "dynamic" sounding headphone. I was wondering if you had any more recommendations of closed back headphones that similarly offer that dynamism in sound and a relatively wide soundstage? Thanks

jesse_n's picture

They definitely sound different from my Sennheiser HD8 DJ (got around the same time so I started using them together in A/B comparisons). One thing I noticed was, the M&D's had a "frothy" sounding mid-bass. It occurred to me this was an awful lot like the sound of an un-stuffed speaker cab (I'm a DIYer). So I opened them up - Lo and behold, here's yet another headphone "maker" that seems content with just sourcing drivers and putting them into empty shells without integrating them together. The drivers have the typical damping sheets taped on the backs, but the shells (and yes, they are plastic and say "ABS") are completely empty. So I played with various amounts of fiberglass stuffing, and ended up with a modest amount that made a HUGE improvement. I can't understand why so many detailed reviews of these headphones don't even mention this "unstuffed box" effect in the mid-bass. It's quite apparent and quite easy to fix.

Tiramisu's picture

I just bought these and the tonal balance seems like a complete joke to me. Compared to my AKG 712, they have nothing above the midrange. The measurements showing significant drop off are dead on to my ears.

I'm going to try the suggestion to use polyfill to tone down the boom and see if that helps. But seriously, it's like listening with a bad headcold. Direct A/B comparison with any good headphones should show it.