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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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Sennheiser HD630VB


HD630-VB The Sennheiser HD630VB is a closed over-ear dynamic headphone.  It is not just another headphone with a DJ-look  though. Yep, it is bulky. The feature that sets this headphone apart from other headphones is the VB-part in its name. VB stands for Variable Bass.
Yes, this certainly not the only headphone around which has such a feature. The AKG K181, K267 Tiesto and the Beyerdynamic Custom One Pro come to mind.
All of these have their tuning options on each cup and are acoustical in nature (a port being changed). The HD630VB is different and uses a passive electrical circuit to change the settings… step-less. This means the setting for this is done on one earpiece and works for both channels at the same time. VERY easy to adjust the bass when you are listening.
It retails for around € 450.- . Yes, a steep price but this headphone offers good sound quality, portability and above all the variable bass setting which is quite useful when you are playing random music files with substantially varying amounts of bass.
The headphone sits VERY comfortable on the head.
As most people are aware apple devices remotes don’t work on other devices and vice versa. The HD630VB has a small switch on it where you can select the Apple or other devices.


Type: Over ear, closed
Usage: Home, portable, office, studio,
Driver type: dynamic
Pads: replaceable pleather
Foldable: Yes
Headphone cup connector: fixed
Cable entry: Right side (unusual, most headphones have their cable on the left)
Cable: 1.2m 3.5mm TRRS with inline mic/remote
Driver size: 40mm (offset to the topside in the cup)
Max power rating: 0.2W ?
Max. S.P.L.: 120dB ?
Impedance: 23 Ω
Efficiency: 98dB/1mW  (114dB/1V)
Weight: 400 g.
Clamping force: low
Accessories: carry bag, 3.5mm TRS to 6.3mm TRS adapter, manual

Sound description:

Will be added later…


Because of the Variable Bass setting the frequency response will vary depending in setting of the dial. Even though the dial is step-less it has a few markings which are used to measure the response at.
Below the frequency response of the HD630VB (Left, Right) in the ‘middle’ setting.

FR HD630 (mid)

Strangely enough the driver matching seems quite ‘off’ below 400Hz.
I have no idea if this is only present in this one or is common for the model. The subbass and bass are clearly present. The dip around 300Hz ensures bass won’t bleed into the mids or sound ‘bloated’. At the same time the bass becomes less well integrated in the mids.
The mids are clear and have excellent presence/clarity. The treble is somewhat accentuated. A bit ‘toppy’ with some recordings. The overall treble signature is still pleasant and clear and not sharp or sibilant.

Below the frequency responses on various settings (left channel only).

HD630 VB settings

The min and ‘1‘ settings seem to be the same. Mid setting ‘3’ (neutral), max setting ‘6’, and min setting ‘0’. bass is affected below 200Hz except at the max setting and ‘5‘ setting.
The bass becomes a bit too boomy for my taste at those settings. For me the optimal tonal balance setting was somewhere between 3 and 4. The tonal balance was quite realistic with well recorded music in that setting. I never felt the need to go below setting 2 even with quite bassy music. With some pop music the 4 and sometimes 5 setting gave a more pleasant sound. And this is the strength of this headphone. With bass-shy recordings you can quickly dial in bass to your taste. When the next song is well recorded it is just as easily adjusted. This is a bigger ‘thing’ than one initially might think though and a really great feature. MUCH more handy and faster than having to adjust the bass on your phone/DAP/tablet.


output resistance / damping-factor

It would appear as though the tone control is passively done. Most likely with a variable resistor (potmeter). This also means that the frequency response could be quite dependent on output resistance.
To test this the headphone is measured via a low impedance amplifier (0.2Ω) and a high impedance amplifier (120Ω). Alas I tested this on the right channel only (in mid setting) and not on the left channel. Also only in the mid setting. When I have a chance I may do some more tests. Below the right channel in mid (3) setting driven from 0.2Ω and 120Ω.

FR HD630 (mid) R 120
Obviously the impedance rises somewhat above 10kHz. The difference in tonal balance on this setting is substantial. It becomes VERY bassy and ‘fat/bloated’ sounding. It is an even bigger change as when the dial is set to ‘max’. +8dB is VERY audible.
This headphone thus should ONLY be used from low output resistance amplifiers (< 10Ω) which, fortunately, almost all portable equipment is.

Below the distortion plots of the HD630VB : (only Right channel shown)
Note that this headphone was measured at ears-unlimited-logo where  background noises were present in the demo room. As this is a closed headphone distortion levels and spectrum plot performance may only be slightly better in reality than as shown on the plots.

The distortion products are shown in dB. This plot is in the ‘max’ setting as the distortion levels were highest there (left channel)

Dist HD630 L max

The distortion profile is typical for a dynamic driver. Higher 2nd harmonic distortion in the bass area. 1% distortion around 50Hz pretty good. At 300Hz the distortion appears to rise but am quite certain this is not there and caused by ambient sounds. The distortion in the all important mids are VERY low (<0.1%). The slight peak around 6kHz is just 0.2% which is an excellent value.

Dist HD630 L max percent

Below the CSD of the HD630VB in mid (3) setting (Left and Right channel are superimposed)

CSD HD630 mid

The CSD shows some slight ringing around 3kHz (you can also see it in the distortion plot) and at around 7kHz. The 3kHz one is short and because the ear-canal rings naturally in that same frequency band it won’t be audible. The 7khz peak and ringing are most likely audible with some music. The small hint of ‘over-detailed / slight sharpish’ treble with some recordings are most likely the audible effects.

Below the spectrum plot of the HD630VB (Left channel)
Sectr HD630 R mid
Some issues become clearer in this plot. The signals around 1.2kHz is caused by ambient sounds. The signals between 2kHz and 4kHz are really there. Some ringing between 7kHz and 10kHz as well. This is shown more clearly in the CSD though.

By lack of oscilloscope shots (not enough time to measure that) below a step response plot of the HD630VB (Left channel)step.png

The step response clearly shows the ringing which isn’t well damped. In the mid setting the tonal balance is quite good. On the left one (1 setting) the roll-off in the subbass is visible. Treble and mids are still the same. On the ‘5’ setting the bass is overpowering the mids and treble.


The sound quality of this headphone is quite good and nearing HD600/HD650 quality.
Discriminate listeners may find the lows and treble of the HD600/HD650 slightly more ‘real’. Still the overall tonal balance and sound quality is well above a lot of other headphones. The most important part here is that it is designed for portable applications and is easily driven from DAPs, phones etc and above all the VERY easy and very effective tone control for the bass. It can be turned from bass shy to bassy in a moment.
The large dial is very easy to operate.
Indeed ‘portable’ hifi-sound which is tunable in the lows.
It does have some disadvantages, weight (400gr) is not exactly light weight. the size… it is big and bulky. Another point of criticism is the cable … it is fixed.
The reason for this is the switch on the headphone which requires more than 4 wires and thus a TRRS connector would not have been enough.
Recommended for those seeking a high sound quality driven directly from a phone.

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