HD414
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published: Jul-16-2021, updated: Dec-13-2021
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.
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.
Sennheiser HD414
The Sennheiser HD414 is an open on-ear dynamic headphone. This is a very early one. It has an unusual high impedance of 2000Ω (2kΩ). It is from around 1970. Even today the HD414 still is the best sold headphone.
It has become a legendary headphone.
There were two different impedance versions of this headphone. This is the 2kΩ version which was only around for a few years. After that they became 600Ω, which is still very high for today’s standards. The 25 year anniversary version was 50Ω. The colour changed to black but the iconic yellow foam pads remained the same. Sennheiser, till this day, still sells new pads for this headphone. Some of the very first ones had very dark grey foam pads.
The HD414 had a cable with a DIN ‘dice’ connector + a 6.3mm TRS converter. On the headphone end it has the all familiar Sennheiser 2-pin connector.
Nowadays there aren’t many headphones around in this impedance range but they still exist. The advantage is (was) it can be driver directly from the output of a power amp and one could use lots of them in parallel in studios on one amp without needing a distribution amp. You need a more ‘serious’ amplifier to make it sing a bit more convincing. Think of headphone amplifiers that can supply a high power output level in 300Ω headphones, OTL tube amps and speaker outputs of integrated amps.
The headband is made of 1 piece. The construction is very simple yet durable (over 50 years old). It still functions as when new. The headband is wide but not padded and together with the small weight (135 gram without the cable) it is quite comfortable for an on-ear headphone.
Despite its sober construction it functions pretty well. The cups can easily swivel and extend far enough and wide enough to fit most if not all heads.
Comfort is quite high. The pads do get a bit warm on the ears but not sweaty. Clamping force is low yet stays put on the head, also due to its light weight.
specifications:
Type: on ear, open.
Isolation: none
Usage: home and studio
Driver type: dynamic
Pads: foam
Foldable: No
Headphone cup connector: 2-pin Sennheiser connector.
Cable entry: dual sided
Cable: 3m cable with DIN ‘dice’ connector + 6.3mm TRS Jack converter
Pad dimensions: outer diameter = 70mm
Driver size: 30mm
Max power rating: 0.1 W
Max Input Voltage: 14 Vrms (40 Vpp)
Max drawn current: 7 mA
Max. S.P.L.: 122 dB
Impedance: 2000 Ω
Efficiency: 102dB @ 1mW
Sensitivity: 99dB @ 1V
Weight: 135 g.
Clamping force: low 2.4N
Accessories: 3m cable with 5-pin ‘dice’ DIN connector with 6.3mm TRS jack.
Sound description:
Bass is not there at all. No warmth either. This headphone is only about the mids. And not even good ones at that because of the emphasis of upper-mids / lower treble. This makes the HD414 sound sharp and grainy. Treble extension is not there either, no smooth treble, no air….. just sharp mids.
The newer versions, and certainly the Sennheiser 50 year anniversary version (1995) of the HD414 will have better drivers and better sound quality.
Measurements:
Below the frequency response of the HD414 (Left, Right)
Channel matching is excellent. Obviously this wasn’t an issue about 50 years ago… Bass rolls off audible below 200Hz. Mids are well… ‘flat’ from 200Hz to 1.5kHz with a substantial 10dB ‘bump’ at 3kHz. Frequency extends to 10kHz. This was probably acceptable extending all the way up to 7kHz.
compared to
The only headphones I measured from a similar era are the Pioneer SE305 (coconut) and Sennheiser HD420SL
The HD420SL, however is a lot newer. Below the HD414 vs HD420SL.
It’s evident the HD420SL has much more bass and treble extension and is lacking the 3kHz peak.
It has been coined a few times that the Koss KSC75 and HD414 have certain similarities.
When looking at the plot comparing the HD414 and KSC75 it is obvious there are similarities but also substantial differences. They do not sound alike but do share some traits.
Both headphones are over-ear, have foam earpads and a similar upper treble peak giving them a bit too much clarity. The response from lows to 2kHz is very smooth. There are also substantial differences. While both have rolled-off lows bass extension from the KSC75 is much deeper. 40Hz -3dB vs 120Hz -3dB. There is a very audible difference in body and ‘warmth’. Also treble extension is much better in the Koss and goes up to 16kHz where the HD414 drops down after 10kHz.
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 a low impedance amplifier (0.2Ω) and a high impedance amplifier (120Ω). On a higher output resistance amplifier the output level will be lower. Because of its high impedance the level is only 0.4dB lower at 120Ω so the plot below is not even corrected for this amplitude difference.
It is clear that output resistance is not of any importance here. Even a 600Ω headphone output resistance, which was not unusual in those days, isn’t a problem.
Below the distortion plot of the HD414 (Left channel shown)
Below the same data but shown in a percentage scale instead of a dB scale.
The 2nd harmonic distortion in the bass area is, expectedly, not very low and reaches about 2% in the bass are. The 3rd harmonic distortion (which points to clipping alike behaviour) in the bass area is also reaching 3%. From 200Hz to 2kHz the distortion is about 0.5% which is not bad for a 50 y.o. headphone.
Distortion around 3kHz is peaking at 1.5% which are audible levels. These distortion levels are at 100dB though (at 3kHz).
Below the phase response of the HD414
Below the CSD of the HD414 (Left and Right channel are superimposed)
It is quite clear that the 3kHz peak is a resonance. No resonances at other frequencies only at 10kHz a small one that is also visible in the phase response plot.
The Group Delay plot below also shows nothing strange.
Another form of looking in the time domain is the spectrum plot
. The amplitude is colour coded and both the time scale and frequency scale differ as well.The lows are very well damped and ‘clean’ there is no resonance showing there. The dark blue ‘noise’ in the upper mids is very low level (about 55dB below the signal) so isn’t problematic.
By lack of oscilloscope shots below a step response plot of the HD414 (Right, Left)
)The This is a very poor response. No bass extension, The harsh uneven response is visible in the first peak which is much too high.
square-wave and impulse response
Below 40Hz and 440Hz square-waves and 100μs impulse response, stimulus (and target) and measured response.
Errmm … yes, hard to believe this is the best sold headphone and was often lauded for producing quality sound. The huge 3kHz resonance (which gives the headphone over the top clarity) is clearly visible.
summary
The original HD414 is an icon in the headphone world. It is very comfortable headphone with a simple but effective design.
Maybe worth owning when you find it cheap just for the sake of having some ‘history’ in your hands. Don’t buy one thinking it sounds great. The 50 year anniversary version may well be better sounding though.
This headphone is part of headphone history and that’s where it should stay.
The only things that these headphones are somewhat good for is listening to spoken word and maybe, when you don’t mind a lower fidelity some nostalgic girl and guitar music or piano. You will need an old receiver or headphone amp that can at least drive 600Ω headphones. It is 3dB less sensitive than the HD650 and badly needs some EQ in the lows and at 3kHz.
DIY-Audio-Heaven 