Enclosure type: circumaural, closed.
Weight: 180g.
Headband type: plastic, self-adjusting.
Cable: OFC, 1.3 metres, fixed Y-split, plus 1.7-metre extension, standard stereo minijack.
Diaphragm diameter: 35mm.
Frequency response (according to Denon): 10-24000 Hz.
Nominal impedance: 28-ohm.
Sensitivity: 103 db/1mW
Maximum input power: 1 W.
Suggested retail price range in Japan: 5000 yen.
Japan release date: January 31st, 2008.

Denon AH-D501 are a brand-new model for 2008. Or rather, mostly new, as the AH-D501 are an improvement of earlier AH-G500.

Denon AH-G500

At the Denon website, they’re described as “on-ear”, which is a synonym for “supra-aural”. In reality the AH-D501 are circumaural headphones. Here’re the AH-D501 next to supra-aural Sennheiser PX100.

The AH-D501 have very attractive looks, both in box and unboxed.

(Denon stock photo)

Construction

The AH-D501 are built of plastic, with synthetic leather cushions and the usual black acoustic foam pads. The plastic looks durable and likely won’t break in the headphones’ lifetime.
AH-D501 are comfortable and lightweight, but the fit can be somewhat too loose - and they can slip while the wearer is walking. This can cause some minor acoustic power bleeding. Unlike the AH-D1000 with its magnesium, adjustable “clicker” frame, the AH-D501 have a plastic “self-adjustable” headband in the style of AKG Studio-line headphones. They don’t fit as snugly as the AH-D1000, but with some slight adjustments the cups can fit properly - the trick is pressing softly, then moving cups slightly downwards over the ears, until cushions seal well.

Electrical Properties

The AH-D501 have an uncommon impedance of 28 ohms. In theory, this means they require less voltage (the higher the impedance, the more current is required). But, headphones with a lower impedance present a more difficult load to an amplifier. A low-powered device like a small portable player running on a 1.5V battery will have to bear with driving the headphones through a headphone amplifier. The higher the impedance, the more of a difference a headphone amplifier makes; lower impedance makes the amplifier act less as an intermediate current booster and more as a relay.

This uncommon impedance made the CMoy amplifier distort easily at serious volume - lower-impedance headphones like the AH-D501 are more of a strain for CMoy amps. AH-D501 cannot be driven as loud as the AH-D1000 either: the Sony D-NE500 portable CD player, running on a single AA battery, managed to drive the AH-D1000 to full volume, but not the AH-D501, which remained rather quiet (ironically, quiet enough to let street noise be noticeable). So even though AH-D501 and AH-D1000 have the same quoted efficiency, 103 dB/1 mW, AH-D501 are not as efficient due to uncommon impedance and somewhat shallow dynamics.

A possible problem for owners of Apple gear is, again, the uncommon impedance of AH-D501. Apple computers (and IPod players) have headphone outputs designed for 32-ohm impedance. An IPod might not do that, but here the Apple Powerbook G4 had killed a couple headphone sets with a nominal impedance of 24 ohm. 28 ohm isn’t that far from 32 ohm though, so there shouldn’t be any trouble.

Playback

Out of the box, AH-D501 were somewhat disappointing. Next to the AH-D1000, they do sound somewhat shallow and bland, duller. Combined with the harshness of new headphones, this could mean only one: burn-in.

And burn-in they did, playing a mixture of powerful tracks - anything from English rock (Godflesh) to 96/24 symphonic demos, also playing through perhaps the best burn-in album ever, Mick Harris’ Hednod Sessions.

This album, when played through appropriately powerful speakers, can do what the cover shows.

Of course there was the usual burn-in material - pink noise, and several tracks of silence, off the downloadable Audiotest CD. So after a night spent locked away in a carton box with clothing, the headphones have done at least 14 hours of playing. And they softened up. At which point they might as well be compared to other headphones…

Like the AH-D1000. Here the impression is clear - the AH-D1000 are much, much cleaner, with exciting lifelike dynamics (first impression from the AH-D1000 is just how lifelike their reproduction is), powerful reproduction of music, excellent detail and imaging. The AH-D501 by comparison are more constrained, with a shallower dynamic range, and slightly veiled. They are duller than the AH-D1000 and really not a match at all. The difference in liveliness and clarity between the AH-D1000 and AH-D501 is perhaps worth more than the price difference.

And the funny part… In the US, street retail price for AH-D501 is going to be ~$70-$100. Which means they’re competing with Sennheiser PX100 and PX200, with Sennheiser-suggested retail price of $80. So how do they fare compared to the PX100? Pretty well actually. A quick switch from the PX100 to the AH-D501 suddenly brought life to music and showed the details and ambience that were missing, made the music breathe. The PX100 have a tad sharper high frequencies, but the AH-D501 are a lot more revealing when it comes to ambience and soundstage. The PX100 (and PX200) are very, very dry-sounding next to the AH-D501, lacking life and breath, though jolly in their dynamics.

AH-D501 are quite neutral in their presentation of music, monitor-like even. They are in the class of headphones that reveal all instruments in a mix, never trying to hide any subtlety. Soundstage is quite wide and detailed. They’re also rather unforgiving to sources; the Sony D-NE500 player sounds rather shallow and cold with the AH-D501. There was going to be a test with an Apple IPod digital player, but the owner’s never shown up; however, the AH-D501 ought to work fine with the more powerful rechargeable-battery digital players like the IPod, Cowon players, Meizu M6, etc.

AH-D501 do manage a good rumble without any trouble. The “Hednod Sessions” are two CDs of mostly slow, ambiental drum’n'bass with very powerful basslines and percussion. AH-D501 handled the “Hednod Sessions” impeccably, never distorting or losing a note. The monstrous bassline in Jesu’s “We All Faulter” also played without any problems (that bassline can bring any speaker set to gurgling distortion). Denon quotes a shallower frequency range for the AH-D501 - 10-24000 Hz, against 8-37000 for the AH-D1000 and AH-D1001. AH-D501’s dynamics, not being as deep (or tall) as of the AH-D1000, can also highlight the bass more than the AH-D1000.

The only slight problem with AH-D501 is their relative dullness. They don’t make hi-hats sparkle, they do steal away some of the high-frequency energy, but the AH-D501 still manage to paint everything accurately. There’s a certain veil over the higher frequencies, but overall they’re relatively clean. They’re also somewhat dark. They tend to sound a bit more like CD-booth closed auditioning headphones than cheery open portable headphones, but, as usual with Denon headphones, for closed headphones they sing, and the usual boominess, honkiness and muffledness associated with closed headphones is not there. If it weren’t for the isolation, AH-D501 could be mistaken for open headphones.

Isolation

They do isolate. Not as well as “full-blown” closed monitoring headphones like Equation Audio RP-21, but everything becomes muted when they’re worn. They do provide a “what did you say?” level of isolation. Hum and whine of computer fans become very muffled with the AH-D501 worn, and unnoticeable when anything’s playing. Unlike the AH-D1000, which are designed more to isolate music from whoever’s outside the headphones, the AH-D501 isolate the external noise from whoever’s listening to music with the AH-D501 on. Which is an improvement that likely extends to AH-D1001.

Conclusion

The AH-D501 are good value for the money. Not a miracle of course, these are headphones in the same class as the Grado SR60 - around the $70 mark, but with the added advantage of being closed. Their somewhat unusual impedance can make them a difficult drive for Chu Moy headphone amplifiers. They are quite good in their class, and will give the likes of Grado SR60, Sennheiser HD215, etc. a run for the money.

For anyone used to much cleaner headphones like Denon’s own “thousand” line - AH-D1000, AH-D1001, AH-D2000, AH-D5000, - AH-D501 will be a disappointment. The difference between AH-D501 and AH-D1000 (or -1001) is well worth the money. The same for portable player listeners looking for excellent portable headphones - the AH-D1000 (or AH-D1001) are more compact, fitting more snugly with an adjustable headband, and a musical revelation. The Denon “thousand” series are really that great; it’s not the AH-D501 that aren’t good, but the “thousand” models are truly excellent.

EBay merchant Ubuycheap stocks Denon headphones at a quite good price, though he’s out of AH-D501 stock at the time of writing. He also stocks AH-D1001, for a sale price about $40 less than Audiocubes and far less than retail stores. He’d shipped the AH-D501 quickly and accurately outside the US, and all items he sells can be shipped internationally.
And here’s the full listing for all Denon headphones at EBay.