Released back in 1988 (yes, more than 30 years ago!) the Sennheiser HD 25 was aimed mainly at film-making and broadcast professionals. The main design goals at that time were sound isolation and accurate tonal response so that broadcasters could hear themselves clearly. Over time the HD 25 has found itself useful for many applications. From official headsets of the Concorde supersonic airliner to covering a single ear of many DJs, the HD 25 excels when reliability and isolation are paramount. But what about accuracy? Read on to find out whether a 31 year old headphone can be useful for the modern sound engineer on the go.

  • Superb isolation
  • Low THD
  • Field repairs possible without tools
  • Generally very durable
  • All parts available from Sennheiser

Pros list with SoundID Reference calibration

  • Tonal neutrality
  • U-shaped sound signature
  • Not exactly comfortable
  • The cable connection to the earcup is a known failure point
  • Treble rolls-off after 15kHz
Use cases Best use case:
Location sound
Tech specs Type
Closed back, On-ear
70 Ohm
threaded 3.5mm angled jack
Screw-on 6.3mm adapter
140 g (without cable)
Require headphone amp
Headphone amp

The HD 25-II is right on the border between efficient and inefficient headphones. On smartphones and dinkier laptop headphone jacks, one might feel the lack of volume headroom, whilst with most modern audio interfaces the HD 25-II should do fine. The isolation provided by these headphones also means that SPL can be kept down because it doesn’t need to compete with the outside din. 70 Ohm impedance shouldn’t be a problem and allows the HD 25-II to be used with up to 9 Ohm output impedance headphone outputs.

Build quality

Sennheiser has a long tradition of manufacturing headphones for professional applications and the HD 25-II embodies much of their material science and industrial design know-how. When you pick up the box the HD 25-II gets sold in, it might feel that they’ve forgotten to put the actual headphones in. At only 140 grams, the headphone feels almost like a toy, nearly everything is made of plastic, save for the screws and actual conductive surfaces. Only once you’ve used them for a while you realize that the plastic Sennheiser has used stands up to everyday abuse perfectly. This plastic is unbreakable, you can bend it obscenely and it will flex back. Having owned these headphones for 2 years, only two weak points presented themselves. The cable connections at the earcup can start losing contact, especially if the cable gets unplugged frequently, the fix is to bend back the contact surface with a needle. And the ratchet mechanism which holds the earcup to the headband can become loose in time. Other than that, the HD 25-II is indestructible.


The U-curve strikes again! Mids to upper mids are okay, but the enormous boost at 100 Hz will accentuate every bass instrument string, or synth. The 8 kHz peak might be useful to pick out a hiss, but for mixing or mastering it’s a no-go. The peak will overemphasize overtones, making the engineer attenuate them too much thus resulting in a dull sounding mix. What’s more – the treble response drops like a rock after 15 kHz, which might not be an issue for older folks, but people under 30 will certainly feel a loss of “air”. Generally, this frequency response isn’t drastically worse than that of other on-ears at this price segment, like the Audio-Technica ATH-M60x for example.

Channel balance

Channel balance on the HD 25-II is fine, which isn’t surprising for a Sennheiser headphone. What can mess up the channel balance is a problem that’s inherent in all on-ear headphones – the sound varies, depending on the headphone’s position on the listener’s ears. This is another strike against using the HD 25-II where sound quality is critical.


You don’t want to be wearing them for too long. The pads are covered in a nylon-like cover which provides superb outside noise isolation, however, it can get rather sweaty after a few hours. The headband itself isn’t too bad, but the HD25-II relies on a rather strong clamp to keep the earcups snug on your ears. The clamp can get especially brutal if the listener is wearing glasses because the legs will probably get pushed into the temples of one’s head. In other words – you’re not buying the HD 25-II for comfort.


This is tricky, as Sennheiser offers the HD 25-II in many different packages. The HD 25-II can be bought in the “HD 25” package for 150$, which is barebones with a single 1.5m straight cable. This is a great deal, as you get the most useful things cheaper than most alternatives like the Audio-Technica ATH-M60x. The more expensive “HD 25 Plus” package throws in an extra coiled cable, a pouch and a pair of plush ear pads which are more comfortable, but have less low end extension and let more sound in.

Total Harmonic Distortion

Generally, harmonic distortion is inaudible, which is commendable. The distortion peak at 6khz is narrow enough to not cause trouble unless precision work is to be done around that area. Not bad for a 31 year old driver!

How accurate and consistent is the correction effect among different listeners?

Consistency is mainly hurt by the fact that the HD 25-II is an on-ear headphone. Fit issues will change the sound, which is why one should stick to over-ear headphones when sound quality is paramount.

How much do they differ pair to pair in terms of frequency response?

Consistency in manufacturing is Sennheiser’s forte. The HD 25-II is no different and shows very good consistency. Again, real-world consistency will depend on the fit.


6.9 / 8.3 / 8.8

Sound rating is a weighted average of Frequency Response, Adaptiveness, Harmonic Distortion and Channel Balance scores, with Frequency Response and Adaptiveness having the greatest influence.

5 / 9 / 10

The flatter the frequency response – the higher the score. When evaluating the frequency response score with the Average calibration profile, the pair to pair consistency of the given model is taken into account – if we have measured a considerable frequency response inconsistency among multiple pairs of the given model, the score drops, as the profile loses accuracy. Individual calibration will grant perfectly flat frequency response.


Adaptiveness shows how capable these headphones are at delivering the same perceived frequency response to any listener. Headphones with high score will sound nearly identical to everyone.


Harmonic distortion – the lower the Total Harmonic Distortion (THD) figure, the higher the score. Headphones with prominent 3rd harmonic distortion above 100 Hz will score lower.

9 / 10

Channel balance – the closer to identical the frequency response of both channels, the higher the score. Individual calibration delivers perfect channel balance.


Comfort – shows if headphones can be used for long listening sessions comfortably. Every model is tested by at least a few individuals.


Build – evaluates how well the headphones are put together, the materials used and indicates the expected longevity. Easily replaceable (and easily available) parts will boost the score. We don’t do any stress tests and very few models are used for longer than a couple of days, so this is a fairly subjective score.


Value – indicates the price-performance ratio of the given headphones and how they stack up against the competition. High score means that you won’t find more neutral sounding alternatives for the price.

Out of the box
With SoundID Reference calibration


After 31 years, the HD 25-II has found happy users in its intended broadcast segment, however, DJs and drummers adore it even more for its superb isolation. Ultimately mixing engineers should look elsewhere, unless forced to make do.

Final Rating

With SoundID Reference
Calibration Enabled
Without SoundID Reference

Remove coloration from your headphones
with SoundID Reference from Sonarworks

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