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published: April-10-2021, updated: May-10-2021

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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 pinna-less flat-bed 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.

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 HD330

The Superlux HD330 is an open budget monitoring headphone. It sells for around € 30.- in the E.U.
It is available in a 150 Ohm version. Yes, it does look like the DT770 Pro but the DT330 is an open version so closer to the older DT990.

The headband is a cheaper made, looking and feeling Beyerdynamic ‘copy’. The drivers inside are of Superlux design though and in no way a copy of Beyerdynamic.

The headband padding is soft and covered with thin pleather so one can expect it to flake and become ugly quite quickly. The cups can tilt enough and swivel  little. The headband height adjustment works but was a bit loose on one side. This will fit most heads though.

The cable is fixed, so not replaceable. The cable is coiled and 80cm long in not stretched conditions when new. When stretched for a while it will not go back into the same state any more. Fully stretched it can reach 3m. It terminates in a 3.5mm TRS jack with a screw-on 6.3mm adapter.
The cable is somewhat microphonic. This means touching the cable is audible in the cups when no music is playing.

There is little isolation from outside noises as this is an open headphone. The pads are pleather covered but the foam inside is firm. Comfort is not very high and the pleather material is bound to flake rather sooner than later. Clamping force is not high so it does not clamp hard on the head. There isn’t much room for the ears though. Pad depth is 19mm.


Type: Over ear, open
Usage: studio
Driver type: dynamic
Driver size: 40 mm
Pads: replaceable, pleather on stiff foam.
Inner pad dimensions: diameter: 50mm,  depth: 19mm.
Fold-able: No
Headphone connector: fixed
Cable entry: left side
Cable: coiled 0.8m to 3m fully stretched
Power rating: 0.1W
Max. Voltage: 4V
Max current:  30mA
Max. S.P.L.  118dB
Impedance: 135Ω (measured)
Efficiency: 96dB/mW (105dB/V)
Weight: 300 g. 
Clamping force: medium/low
Colour: Black with slight blue logo.
Accessories: 6.3mm adapter, hard plastic case.

Sound description:

Boomy/hollow but not well extended in the lows, clarity is lacking, treble is elevated compared to the upper mids which ‘enhances’ details but treble quality isn’t high quality and gives it some undesired sharpness.
Not ‘dynamic’ sounding. Treble is a bit coarse with a sharp-ish feel to it.

For monitoring the headphone is usable. The elevated treble will let you hear details you otherwise may not hear.  Never mix or apply EQ to recordings based on the sound of these headphones, the frequency response is not suited for this. Not a headphone for enjoying music when you are focussed on sound quality.


Below the frequency response of the HD330 (Left, Right)

The lack of real bass extension is obvious as it starts to drop-off below 50Hz. The lower level between 1kHz and 6kHz is responsible for the lack of clarity. The treble above 6kHz rises again to the same level of the lower mids/bass and thus isn’t perceived as elevated but is responsible for the sharp signature.

compared to

The closest it compares to (that I measured) is the cheap behringer BH470 but this is a closed headphone.
Below the BH470 vs the HD330.

Another headphone with a similar tonal signature is the AudioQuest NightHawk. The NH has better bass extension and overall sound quality so this is not a poor man’s NH.  Treble quality differs as well but in overall tonality described as warm/bassy/laid-back both share this.

Below a comparison with the closed ‘cousin’ the closed Superlux  HD660 Pro. This one has very similar if not the same drivers but very different pads. The HD660Pro, however, has a very audible and unpleasant treble peak.


Seal can be an issue with closed-back headphones. Breaking the seal (improper fit on the head) usually means a loss of (sub)bass. Seal breakage can be caused by different facial contours, glasses or hair between pads and head. Open headphones usually are less seal dependent.
Below the effect of different levels of seal breach are shown .
Perfect seal, Seal broken with a pair of glasses, seal broken using a 6.3mm TRS plug.

Like most other open headphones the seal is not very important to get proper bass extension. Wearing (reading) glasses or having hair between the headphone and ears can slightly diminish the low-bass response.

output resistance / damping-factor

As this is a dynamic headphone the frequency response might be amplifier output resistance dependent when certain higher output resistance amplifiers are used.
To test this the headphone is measured via an amplifier with output resistances of 0.2Ω, at 10Ω, 32Ω 120Ω. These traces are overlaid so tonal balance changes can easily be seen. On a higher output resistance amplifier the output level will be lower as well. At 10Ω the level drops 0.6dB, at 32Ω it is 1.7dB and at 120Ω the level is 6dB lower.

A higher output resistance will give a tiny bit more bass boost. The resistance would have to be substantial before it becomes audible.

Below the distortion measurements of the HD330 (Left channel).

The plot above is in a dB scale, below the same measurement but in a percentage scale.

The distortion in the lower frequencies is quite high but not really an audible level yet.
NOTE: The actual 2nd harmonic distortion above 1kHz may well be lower than 0.1%. A shortcoming (measurement limit) of my test fixture.

Time domain measurements

Below the phase response of the HD330. There are some steep phase changes which is potentially more audible than a larger but more gradual phase shift. At 550Hz and above 3kHz some phase changes are present.


Below the Group Delay  plot some readers like to see. Around 90Hz there are some pad bounce issues which are also visible in the phase response. Also the response around 550Hz is shown here. Above 600Hz there are no obvious errors in this aspect.


Below the CSD (Waterfall plot) of the HD330 (Left and Right are overlaid)

We see some resonance around 2.5kHz (also seen in the HD660Pro). The 6kHz resonance is high but short lived. Above 10kHz some resonances but all short lived. Also around 550Hz there is some lingering. The energy doesn’t go down fast. Seems like a driver issue as this is also seen in the HD660Pro.

Another form of looking in the time domain is the spectrum plot. The amplitude is color coded and both the time scale and frequency scale differ as well.

Below the spectrum plot of the HD330 The ringing around 550Hz is clearly visible. also the resonance around 2.5kHz is visible but not problematic.

Below the step response with a dB scale (so not similar to an oscilloscope plot which has a linear scale).  The step response (Left and Right channel overlaid)

The rising edge doesn’t reach 0dB and also rings a LOT. Bass extension is not great but also not deep. The first 500μs is below the desired level showing the lack of clarity.


First point to address is the lacking clarity and pads. Pleather pads, especially the soft ones, start to flake and become ugly as well as affect the tonality.

Below some experiments with some pads that do not change the tonal balance much but do increase comfort.
Stock pleather pads, Superlux HD681 velvet pads, SRH940 pads.
Bass extension is not changed but tonality is changed somewhat. Especially the Shure SRH940 pads make the sound a bit warmer and make mids a bit more recessed. Treble doesn’t change and clarity remains similar but comfort increases.

Below the HD330 with original pads vs the HD330 with HD660Pro pads (very close to DT770 pads)
HD330 stock pads vs HD660Pro pads

Fortunately there are also pads that change the tonality in a more positive direction.
Stock pleather pads, DT880BlackEdition pads, Grey DT880/990 pads, Cheap e-bay pads (alas don’t know which they are)
These pads make the tonal balance better but at the expense of 10dB in efficiency. This means it will sound half as loud with these pads. Another downside is that the treble peak isn’t lowered. In fact around 7kHz there is even more energy. This makes the headphone less efficient and sharp/sibilant in the treble but comfort increases and mids are now clear and accurate… at least when the treble is lowered.
The problem here is that some toilet paper or other materials do not have enough effect as treble needs to be lowered by 10dB or so.
This can be done by using EQ. Not in all cases it is easy to apply EQ so for this a passive filter is made. This + pads makes the headphone double in price though.

Below the filter schematic for the DIY’ers. Those that cannot make them can have them made by me.

Filter section mounted in the cup on the driver:

The filter effectively lowers the treble peak to desired levels. Below the frequency response of the HD330 fitted with ebay pads + filter versus the stock HD330.The Beyerdynamic pads are more comfortable and similar in tonal balance. The black velour pads have a bit more warmth/bass compared to the grey DT880 pads. Bass response below 40Hz drops a bit. Bass sounds very good but deep rumbles (think movies) are a bit lower in level. The black DT880 pads have slightly more extension than the silver ones.

Distortion also changed a bit.

As did the CSD.

The 550Hz, 2.7kHz and 12kHz issues are clearly a driver issue.

Also the looks changed as I removed the blue plastic plates and replaced it with some black tape.

Below the front side of the HD330 (exactly the same as the HD660Pro) driver.
Below the rear of the HD330 driver and the cup. There is a thin foam inside that is acoustically transparent but keeps dust out. Removing the foam only changes the looks, not the sound.Adding damping materials behind the driver only lowered low bass response which is not desirable.


The Superlux HD330 is a cheap ‘Beyerdynamic’ look-alike but not a clone nor similar in any tonal aspects from the Beyerdynamic range of headphones. It is suited for monitoring but not as a phone for music enjoyment unless you are looking for a very ‘laid-back’ sound (missing clarity). When DT880 Black pads are used the comfort improves and the sound is closer to realistic sound (DT880 alike) sound but with fierce treble. Much worse than what the Beyerdynamics are disliked for. Some EQ or the filter solves this. Of course the pads and filter will cost more than the HD330 by itself.

The fixed coiled cable also will not be what everyone wants but is handy in the studio. This is no DT770/DT880/DT990 alternative despite having the looks. It is a cheap monitoring headphone.

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  1. Anomuumi says:

    Thank you very much for the graphs! Harsh words though, I find these far more enjoyable than rest of the luxes.
    Can you measure with the DT770 velour pads as well (or are any of the ones here close enough)? They seem a very popular pairing with the HD330’s but there’s zero grahps about that combination.

  2. Solderdude says:

    I measured the DT330 with HD660Pro pads (which are very close to DT770 pads).
    It measures horrible (as in V shaped) which some folks like but personally am not interested in.
    See article above.

    • Anomuumi says:

      Tried them myself, they might indeed be even steeper of a V compared to the velvet pads.
      I like neither by default, both do need decent amount of EQ fiddling to sound good.

  3. Nik says:

    Could you please share the frequency response in csv format, this will make it possible to automatically create equalizer settings using AutoEq.
    Thank you!

    • Solderdude says:

      I would not use my measurements to create an ‘exact’ EQ. It is measured to my own target and not measured on an industry standard rig which both are pre-requisites for using auto-EQ.
      My measurements can give you an idea of the rough EQ needed especially in the 6kHz to 15kHz range and below 1kHz.
      So even if I made them available in CSV they will not yield an ‘accurate’ EQ.

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