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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.
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.

post separation
Superlux HD662-EVO









The Superlux HD662-EVO has a similar appearance as the HD681-EVO and is probably why it is called EVO as well.
It has better (more modern looks) than the original HD662F. In that aspect it certainly is an evolution.
Unboxing video here.
It is available in black and white.

The cable on the EVO is detachable, which is an improvement over the original HD662 which had a non removable long cable. It comes with a 3 meter and a 1 meter cable which can also be combined to create an even longer cable. Also a clip is included so you can fix the headphone plug to the cord and can’t pull it out any more. Personally a find the removable cable just fine as it is. It doesn’t come off easily and when the wire gets caught it unplugs itself.

Alas, the cable is microphonic. This means that mechanical contact sounds, when the cable rubs against clothes for instance, are transferred to the cups and can be heard during quiet passages and silence.
This headphone also comes with gold-plated 3.5 to 6.3mm TRS jack connector.
A soft carrying pouch is also included.

Another pleasant addition in the box is an extra set of velours pads. Stock the HD662-EVO comes with pleather pads already mounted.
The pleather (fake, vinyl based leather) is much softer and more compliant than the original HD662 pads. Another welcome improvement !

The headband has a thin layer of rubber on the underside with ‘air filled cushions’.
The shiny surface of the headphone parts are not fingerprint magnets but scratches will be quite visible. Looks-wise it seems to be targeted at younger people or the classier looking Hi-Fi market though.
People with large heads may not be able to correctly place this headphone properly on the head. Just like the HD681-EVO and HD-662-EVO the height adjustment range is too limited.
The height can only be varied 15mm. Most other headphones can be adjusted between 25mm and 60mm. The most common range is around 30 – 40mm.

There are small L/R markings for the non visual impaired users, Braille markings for Land R are also present.
The impedance is around 36
Ω which is excellent for connecting it to portable equipment.

It has large 50mm drivers which appear to differ from the older drivers.
The original HD662 membrane has a different colour and lacks the sticker that is covering almost ¼ of the driver with ‘acoustic damper, please do not remove’ written on it. The HD662-EVO has a 3mm thick felt disc in front of the driver.
This is there to remove the treble peak. But just like with the HD681-EVO it also removes too much upper treble extension.

The efficiency is somewhat higher than that of the HD681-EVO so it plays slightly louder on the same volume setting, that is when comparing both after modifications. It plays loud enough from most portable devices such as mobile phones and small players.

The attenuation from outside noises is somewhat better than that of the HD681-EVO. The latter is semi-closed and thus partly open due to ‘ports’. The HD662 is fully closed. Still some outside noises leak through via the pads.
The clamping force is just right, it doesn’t clamp hard but also stays put when moving your head.

They are a bit cheap plastic looking/feeling. The steel rods connecting the ear-cups are thinner and can be bent and twisted more easily than those of the original HD662. Even though it does have a cheapish look about it you can bend the headphone in all kinds of positions and it always comes back in the original position (within limits of course).
The headphone seems sturdier than it appears to be based on its looks. I don’t think it will break or have parts break off.
Some find the clamping force a tad on the high side.
It can easily be lowered though as can be seen on this instruction video

In the end it is always about the comfort and sound. The comfort part is excellent ! NO complaints there.

The sound is ‘impressive’ on first listen. Where the HD681-EVO (in stock condition) was VERY bassy and dark the HD662-EVO is much more clearer sounding.
It’s like having a sub-woofer strapped to your head.
The strong bass is a deep rumbling type with a clear with way too much treble (splashy, sharp, sibilant) more like the first HD681.

The bass is somewhat dis-attached from the mids. This has the advantage of the bass not bleeding into the mids but also removes ‘warmth’ from voices and lost ‘cohesion’ in that important part of the frequency range. This makes the voices stand out a bit too unnatural and instruments and voices sound a bit too ‘forward’ without being too loud.

The treble is detailed and clear but lacks some upper extension.

Below the frequency response plot of the stock HD662-EVO (with pleather pads)

FR stock new HD662-EVOThe fun bassy character is obvious. The mids are reasonably ‘flat’ but have a rather ‘separated’ sound signature from the bass. It does not ‘blend’ into the rest of the sound.

Distortion plot is shown below.
The distortion is somewhat on the high side for a hi-fi headphone. The distortion peak (6%) around 4kHz is quite high.DIST prod model

The CSD plots of the stock HD662-EVO is shown below, Left and Right channel are superimposed.CSD new EVO stock

Lots of ringing in the 1.5kHz area. Also the 4kHz peak shows resonances. Above 6kHz the treble is somewhat elevated.

The Spectrum plot below shows the 1.5kHz issue a bit better.

spect R HD662EVO

Of course this headphone has gone through extensive measurements and tests to see if it can be improved.
Fortunately the MODIFICATIONS for it are very easy to do and don’t require knowledge about modifying it nor about electronics. The modifications can be found HERE.

After these modifications the sound signature has improved substantially.

The sound description has gone from:

The sound quality of this (modified) HD662-EVO has improved from:

Having a somewhat dis-attached but fun bass but lacking ‘warmth’ and ‘cohesion’. Voices and instruments that stand out a bit ‘unnatural’ but having good clarity. Due to a slightly rolled off upper treble ‘air’ and ‘cymbals’ are slightly lacking realism.

to: Realistic bass response with good subbass extension The midrange is improved (more cohesive), quite dynamic, has a good clarity and sounds very ‘real’. Not ‘warm’ nor ‘cold’. Just … properly balanced and fun. The treble is of good quality with a very nice sparkle and lots of air as well as sounding smooth and detailed. No sibilance, no fatigue, no shrill or harsh treble anywhere.

Below the frequency response of the modified HD662-EVO, Left, Right

Modified EVO FR

Much more realistic sounding but without pthe subbass boost, still with excellent subbass reproduction and extension..
The plot below show the differences between the stock HD662-EVO and the modified version.stock prod (red) vs modified Left

Also the distortion has improved. Especially between 100Hz and 3kHz.
Higher harmonics treble distortion also got better.

DIST modified version

Below the CSD of the modified version, Left and Right channel are superimposed.CSD modified pleather.png

Looks som ewhat cleaner especially around 1.5kHz and above 6kHz.

Improvements can also be seen in the spectrum plot. Especially the 1.5kHz resonance is shorter and has less ‘energy’.

Spects modified

Below the square-wave and impulse response plot of the stock HD662-EVO without the 3mm felt disc (on the left) and the modified version (on the right)


These plots show a substantial improvement. Still there is ringing present at 4kHz. I suspect this is a driver issue. Still the results from the modified version are good, at least given the price point it will be marketted in.

The sound of this modified headphone punches high above its price point.
All that needs to be added is some paper and 2 pieces of cello tape.
It is hard to believe that it only takes 2 very minor alterations to improve this headphone.

Highly recommended for those looking for a good (pleasant) sounding closed hi-fi headphone.

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