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Published: Jun-25-2014

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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.

Frequency response (tonal balance) is the most sound-determining aspect of headphones. A horizontal line shows audible neutral response in the plots on this website. Deviations in different severities at different frequency bands have an effect on the sound character.
The bigger the deviation the stronger the effect.

Below an aid to help determining the sound character of headphones with relation to the frequency response.


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Superlux HD685


The Superlux HD685 is said to be a ‘high definition‘ headphone.
It is selling for around $ 83.- = € 60.- = £ 50
It has 40mm drivers where the HD681’s have 50mm drivers. It comes with 2 cords where one of them has a mic/remote for i-thingies.

Mids and treble sounds good, no piercing highs, nice ‘open’ sound in that the voices are forward and not dull or overly warm.
The highs are soft but unfortunately lack ‘extension’ . This is audible in cymbals and guitar strumming for instance. If you like to hear these finer nuances than this headphone is not for you. If you like big bass and listen to compressed files a lot this headphone could be usable.
Downside… very boomy and ‘hollow’ bass/mids, that is IF you prefer a ‘balanced’ sound (which I do).
The bigger toms, for instance, are exaggerated and sound a bit ‘hollow’, this is the most obvious ‘expression’ of this elevated bass response.
Uncontrolled and ‘fat-ish’ bass but NOT bleeding into the mids as is the case with a stock HD681-EVO.
Personally I do like it better than stock HD681-EVO but am seriously missing velours pads and the treble extension.

HD685 stock
The treble peak isn’t obvious in the sound and sort-off ‘masks’ the lack of treble extension. With some EQ in the 16kHz band it does improve somewhat but sounds a bit ‘rough’ in that area.
Below the CSD (Waterfall plot) of the stock HD685. It shows some resonances around 6kHz and 10kHz and a substantial amount below 700Hz.

csd stock hd685

The hollow and non-controlled bass can be improved with some easy fixes. adding some ‘acoustipack lite®’ and an amount of wool inside the cups (which are very easy to open) and using velours Shure SRH-940 pads makes it sound much better in the bass area. The lack of treble extension remains.

HD685 modified with SRH-940 pads
Bass is lowered but still very ‘big’ but much more controlled.

csd modified hd685
The ringing at 10kHz is gone and the one at 6kHz is shorter. The mids also have improved somewhat. (note the L and R colors in the CSD above have been swapped)

The pads start to feel ‘sweaty‘ quite soon and are of the thicker type pleather kind, very similar to EVO pleather pads.

The cable is about equally microphonic as that of HD681EVO, won’t bother everyone but it does bother me.
Microphony isn’t worse than in many other headphones though.
Didn’t test the remote control as I do not own any i-things.

Fairly good isolation from sounds from the outside and people around you won’t be bothered as this headphone is fully closed.

The hinges are plastic (but look like metal), the cups have a rubbery coating on them.
The headband is very comfortable and soft.
Clamping force is slightly above comfortable but think it can be ‘bent’ a bit looser.
The HD685 has a cheapish feeling to it when holding it in your hands.
Folds up for easy transport.
The cups cannot swivel to the sides but only swivel up and down.
The headband does allow some small ’tilt’ so the cups aren’t too rigid in one direction.
Fortunately the cups have a slight ‘angle’ or offset from 180 degrees and thus fall very naturally over the head

Plays well directly from portable devices and will still have ‘body’ on these devices.

My personal opinion is the modified HD681 and modified HD681-EVO are the better models.
In stock form I prefer the HD685 over the HD681-EVO.
To show the differences between these 3 models below the plots of the stock versions.

STOCK HD681 (gr) vs EVO-velour(red) vs HD685 (blue)
As I do not like these headphones in stock conditions below all 3 of them in modified conditions. HD681(red version), HD681-EVO and HD685

Modified HD685 (blue) vs modified HD681 (green) vs modified HD681-EVO (red)
The HD681 is the one with the largest extension on both sides of the frequency range. The HD681-EVO with about 16kHz in the upper range still sounds quite ‘airy’. The drop-off from the HD685 above 12kHz is quite audible.
The 3dB ‘hump’ of the HD685 is audible but not deal breaking, the lack of treble extension is.

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