Denon AH-D600

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NO SMOOTHING is applied to the shown plots. Most measurement sites have some smoothing applied which ‘irons flat’ sharp peaks and ‘wiggles’. I do not use smoothing because some info about sound quality is lost when plots are smoothed.

Aside from a small correction of the microphone itself also some correction in the lowest frequencies is applied to the plots to compensate for the perceived loss of bass when using headphones. This is described HERE in more detail.
A ‘horizontal‘ frequency response curve on the shown frequency response plots on this website thus indicates a perceived ‘flat’ tonal signature.

ALL measurements are made with a good SEAL on a flatbed measurement rig.
The shape of your head, bone structure, pad size, pad ‘softness,  (compliance), hair or no hair and or wearing glasses may (drastically) change the frequency response of some headphones, so… your personal experience may differ substantially from these plots.

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Denon AH-D600

AH-D600
The Denon AH-D600 is a closed dynamic headphone.  It feels bigger in your hand than it appears to be on the picture. The up – down and left – right swivel of the cups is quite limited. Because of this not every head size may have optimal wearing comfort or fit.
The price point was on the high side with its €400.- price tag (around 2012, no longer available).  The earpads look like leather but are fake leather pads. They start to flake after some time as evidenced by this used pair I measured. The pads are quite soft to the touch and compress and give a good seal. This is essential for deep bass.
It comes with a long and shorter cable with 2x 3.5mm TS (mono) plug with color-coded rings for the left and right cup.
The cable is covered with cloth and quite microphonic. You can hear the cable rub against clothes etc. The headband is soft but has a small contact surface area which takes away some of the comfort.

specifications:

Type: Over ear, closed
Usage: Portable, commuting, office and home.
Driver type: dynamic with bio-cellulose diaphragm (Foster brand)
Pads: pleather
Foldable: No
Headphone connector: 3.5mm TS (mono)
Cable entry: dual
Cable: 3m 3.5mm TRS (+ 6.3mm adapter) to 2x 3.5mm TS and 0.9m 3.5mm TRS  to 2x 3.5mm TS with inline mic/remote.
Driver size: 50mm
Max power rating: 1.8W
Max. S.P.L. > 135dB
Impedance: 25 Ω
Efficiency: 108dB / 1mW
Weight: 365 g.
Clamping force: medium low.
Accessories: Soft carrying pouch with Carabiner hook, 6.3mm adapter

Sound description:

The sound signature seems designed for use with portable devices given the considerable, yet tastefully, boosted lows on most music. The overall sound signature is on the bassy and warm side with a splashy and exaggerated treble. Cymbals are over accentuated.
Bass is boosted and it is just slightly ‘dis-attached’ from the mids.
When you prefer to listen at low volumes only the U-shaped sound signature may well work. At higher listening levels the bass is overblown (yet not in a nasty bloated way) but the treble becomes too much after some time.

Measurements:

Below the frequency response of the AH-D600 (Left, Right)

FR AH-D600

The first thing that stands out the is left-right difference below 300Hz. It is a good 3-4 dB but isn’t very audible. This is because for  these low frequencies the brain doesn’t do its localization thing yet.
The bass boost is similar-ish in shape to Olive-Welti but overdone by a few dB. When one considers O-W bass ‘boost’ is already a bit more than ‘neutral’ you can easily conclude the bass is raised. The small dip at 300Hz makes the bass slightly dis-attached but also ensures the bass doesn’t sound ‘bloated’ or ‘fat’ !
The frequency response for the mids (300Hz to 4kHz) is pleasantly ‘neutral’ as in ‘realistic’. Instruments have a pleasant real-ness to it. The peaky and elevated treble (+10dB !) is not ‘harsh’ sounding but can certainly be piercing at higher levels and with some pop/rock music. The boosted bass won’t mask this.

output resistance / damping-factor

As this is a low impedance (25Ω) dynamic headphone the frequency response of some of this type of headphones, changes when used with a higher output resistance (desktop) amplifier.
To test this the headphone is measured via a low impedance amplifier (0.2Ω) and a high impedance amplifier (120Ω). On a higher output resistance amplifier the output level will be considerably lower. To compensate for this the amplifier is cranked up to the same level (at 1kHz) as the low impedance amplifier. This way the plots are overlay-ed and it is easy to see how the tonal balance changes.

Right channel only, driven from 0.2Ω and 120Ω amplifier.FR AH-D600 R 120
As can be seen the difference is negligible over the entire frequency range. So the sound signature won’t change at all when a higher output resistance source is used.
It also means that the used drivers are mechanically damped and do not rely on electrical ‘damping’.

Below the distortion plots of the AH-D600: (only Right channel shown)
The distortion products are shown in dB.

Dist AH-D600 R

As can be seen in the plots the high amount of distortion in the bass is typical for dynamic drivers. Fortunately high amounts of 2nd harmonic distortion aren’t perceived as such but rather as a ‘warming’ of the bass. The 3rd harmonic ‘component’ is more perceived as a ‘clipping’/’limited’ sound and less benign. Below the same plot but in percentage.

Dist AH-D600 R percent

It shows the bass distortion is quite high. Above 300Hz the distortion should be low as distortion starts to sound as actual distortion from there. The AH-D600 is (and sounds) quite ‘clean’ in the mids. The distortion is down to low levels and 3e and higher harmonics are very low.

Below the CSD of the AH-D600 (Left and Right channel are superimposed)
CSD AH-D600

The ringing for the mids is a bit higher than some of the other headphones. The treble area (>5kHz) consists of several short lived resonances. This isn’t that problematic.
When driven from a higher output resistance amplifier nothing changes that much.

CSD AH-D600 R 120

Above the CSD of the AH-D600 (right channel) via a 0.2Ω output resistance amplifier and also when connected to a 120Ω amplifier. It looks like around 2kHz the driver performs slightly better from a low output resistance source. The difference is extremely small and don’t expect this to be audible. Electrical damping does help a tiny bit here.

Below the spectrum plot of the AH-D600.

spect AH-D600 R

This plot shows bass is a bit resonating and the 2kHz problem area is seen. At 3kHz and 6kHz there are also some short lived small resonances. They are reasonably well damped though so not that problematic.

Step response plot of the AH-D600. (Left channel)
step sine L
On the left you can see that there is some overshoot and (short lived) ringing at a few frequencies. There is a bass boost visible but not as much as the frequency response shows.

This is a quite decent step response.  Below the Right channel.
Step AH-D600 R
The differences between L and R driver are quite visible in this plot. Less amplitude but longer lived ringing and the bass boost is at a lower frequency and a lot more.

The square-wave and impulse response plots below tell the same story.
On the left the Left channel, on the right the Right channel.

sqr.png

The overshoot in the bass on the left channel (upper 40Hz plot) is a lot more pronounced than the right driver. Even though that driver too has elevated bass response.
The left driver seems to be better damped for higher frequencies than the right driver which basically can’t seem to stop ringing. This too is indicative of splashy treble.
On the 100μs pulse it is obvious that the right driver rings on longer than the left one.
Driver matching or quality control seems to be lacking here.
The Fostex TH-X00 headphone I measured has better L-R matching and damping.

 

summary

The Denon AH-D600 is aimed at the portable market. Boosted bass helps here. Boosted treble may not be an issue when listening to Youtube quality recordings.
The bass is (tastefully) boosted, for pop music that is, it has a healthy boost. For better recordings the bass level is way too much and after an hour or so became nauseating for me.
Treble level is too high to be called neutral and will cause listening fatigue after some time.
The mids sound good though and the slightly dis-attached bass makes the listening experience pleasant… that is if you can stand the elevated treble.
I might try to do something about that …. When I do it will be posted.

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