Denon AH-MM400 review: Superlative sound for £200

Price when reviewed

It’s often hard to describe why you love something – regardless of whether it’s a person, an inanimate object, or just a particularly appealing pie, there are those moments where something clicks and a light goes on. For me, that’s the Denon AH-MM400 headphones in a nutshell.

Design and features

When you’re spending this kind of money on a pair of headphones, there’s an expectation that they’ll do more than just sound good. Denon has clearly decided that this kind of person wants earpieces crafted from wood (American walnut, naturally), aluminium, and luxurious-looking cuts of leather. This could have very easily resulted in a bad day in the DFS showroom, but the AH-MM400 have emerged looking rather tasteful. Unless, that is, your idea of high-end design is black brushed metal and maybe the odd dash of silver, in which case you should almost certainly go and read Alphr’s Audeze Sine or B&W P7 Wireless reviews instead.

But whatever you might think of their looks, the build quality here is well up to scratch. The AH-MM400’s adjustable headband and earpieces manage to feel sturdy in all the right ways, largely thanks to the liberal use of aluminium rather than plastic, yet they still fold up nice and small. Squeeze them into the supplied carry bag and, while you’ll struggle to get them in any normal-sized pocket, they won’t take up much room in a bag.


The only mild disappointment here is that the supplied cables feel a tad thin and lightweight. Still, as is fairly common nowadays, you get the choice of two cables, one with standard audio connections and one with an inline remote and microphone for hooking up to a smartphone. You also get a 6.3mm (that’s 5 1/4in for imperial fans) adapter in the box should you need it. Another nice little touch is that the Denon’s right-angled 3.5mm jacks have a narrow plastic housing, so you shouldn’t have any problems with them fouling on your smartphone case.

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Comfort and sound isolation

I have big ears. This can cause problems with certain over-ear and on-ear headphones, and the Denon AH-MM400 are no exception. The soft headband and fake leather earpieces sit fairly lightly on the head, but the slight pressure of the earcups against the edge of my earlobes caused a dull ache after around an hour or two. I suspect the smaller-eared members of the population will find them immensely comfy, but if you can try before you buy, then do so.

The big benefit of the AH-MM400’s closed-back design is that they naturally block out a lot of background noise. They’re obviously not in active noise-cancelling territory, but the whine of air-conditioning units and nearby conversations are instantly dulled as you put them on. Even standing next to the clatter of a rush-hour Tube train, there’s no need to crank the volume high to stop the music from being drowned out.


Sound quality

In contrast to many closed-back ‘phones, the Denons sound immensely rich and spacious – there’s no sense of the music feeling compressed or crunched down in scale, which helps make the most of orchestral works and reverb-laden electronica alike. Guitars, drums and vocals swim out front, and stretch wide left and right across an invisible stage.

What blew me away about the AH-MM400s, however, is just how “right” they sound straight out of the box. It’s the waves of deep, effortless bass that hit you first, but it doesn’t come at the expense of anywhere else in the frequency spectrum. Voices and instruments come through sounding beautifully real and clear, and the treble is delicate and well judged, too.

Another plus point is that the AH-MM400s really aren’t that hard to drive at all – there’s no need to look to pricey headphone amps or DACs. Plug them into a £400 Chord Mojo and you’ll certainly get a little more punch and detail out of them, but my iPhone SE did a fine job without any assistance at all – Apple’s miniature smartphone is more than capable of driving them to decent volume levels.


If I absolutely had to pick holes in the Denon’s performance, then there’s only one weakness worth mentioning: the AH-MM400 are the audio equivalent of a nice cup of tea and a lie-down, which is to say very lovely indeed, but they can sound a little too laid-back on occasion. On some of my trickier go-to test tracks – which include everything from hi-res digital tracks to vinyl records – the Denons struggled to unpick the musical threads quite as deftly as my rather ancient pair of Sennheiser HD 580 Precisions. The music still sounds great, sure, but if you want a pair of headphones that excavates every last minute detail from your music collection, then you might want to look elsewhere.


Since their launch a year or so back, the AH-MM400s have dropped down significantly in price – which is partly why I’ve taken the time to review them now. Frankly, though, I’d rate them highly even at their original £349 price, and given that they’re now going for as little as £200, I’d say they’re among the best headphones you can buy for the money.

Sure, there are open-backed headphones that can trump the Denons for clarity, and active noise-cancelling ‘phones that may be better bet for frequent flyers, but the AH-MM400 strike a superb middle ground. If you want a set of relatively compact, brilliant-sounding headphones, then Denon’s AH-MM400 come very highly recommended indeed.

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