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Sennheiser Headphone renovation for next to nothing...

I've just finished renovating a vintage pair of Sennheiser HD420 headphones that I've owned for over forty years. The renovation was cheap; it was simple and took no more than half an hour to complete.
But why waste time on a forty year old piece of electronics? Surely modern headphones are much better and only a click of a mouse away? Well, maybe, but I love the sound of these old phones and they are so light on my head I can wear them for hours - even with glasses.
I bought my Sennheiser HD420's when they first came out in the late seventies. Since then, they've been my choice in headphones over any newer headphones I have bought or listened to. They are one of the most openly transparent, detailed headphones I have ever listened to - if perhaps a touch light at the bottom end. They do benefit from being driven from a higher voltage source such as a hi-fi amp rather than straight from an iPod or MP3 player but they still sound good on portable devices.
So what was wrong with them? The foam earpads had perished and had literally gone to pieces inside the cloth covers and the headphones were becoming uncomfortable to wear. I tried looking on Sennheiser's web site - and their support site - for replacement pads, but it appears that you cannot get hold of them any more. Such a pity.

There are other HD420 owners on the Internet also seeking replacement earpads so I thought I'd see what else I could do - and hope that my findings are of use to others.

The Sennheiser HD420 earpieces come in three parts. There's the transducer in its plastic housing, an acoustic foam insert and a cloth cover that holds the foam to the transducer. As long as the cloth cover is intact and the headphones work, then all you have to do is replace the pads.
  1. First measure the earpiece diameter (they are 80mm)
  2. Next search Amazon for "80mm replacement earpads"
  3. Buy one of the items that come up in the results
That's the easy bit.

When they arrive you have to replace them. This needs patience, fingers, kitchen paper and an old toothbrush. No other tools or you risk damaging the cloth cover or the headphones.
First you must tease off the cloth covers. Use your thumbnail and carefully ease the plastic surround all round before gently sliding the surround off the transducer.
When the cloth cover is off, clean as much of the old ear pad from the cloth as you can (in the picture all that orange crud is the old earpad).
Now, with a toothbrush (and nothing else!) gently brush all the compressed and rotten old earpad from the transducer. Be careful - the white in the transducer is material and this can easily be damaged if you use too much force. Remember it is forty years old!!

Here you see the new earpad with one of the cloth covers
Here you see the new earpad in position over the transducer
To re-fit the new pad and the cloth cover, first tuck the pad into the cover as seen here.
You now need to gently get the cover back on the transducer. I did this by holding the plastic surround in place with one finger while I gently eased the surround back into place around the transducer. The hardest part is the last inch so make sure that the last inch is away from the wire and the headband so you have the most control. Don't use tools or too much force or you'll tear the cover. Of course you can take the transducer off the headband (it just pulls off, but remember it is old so it could be brittle) and you can also pull out the wire, if this makes it easier. I decide not to do this and did not have any real issues, but the choice is yours.

Finally the restored Sennheisers, all padded out and once again, fit and ready to listen to.

Total cost?  less than £3.00 and under thirty minutes. Satisfaction?  Priceless.  :)

54 comments:

  1. Hello,
    Great post and nice tips on how to clean the headphones. It helped me a lot and thanks for sharing.

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  2. Your post triggered me to fixed my Sennheiser HD420
    Thank you

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    Replies
    1. Thanks for your comments. I hope you found the fix as worthwhile as I did.

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    2. Yes it did , the sound is a litle bit more spacial and the comfort a lot higher .
      They are now even warm at my ears !!!
      I order two pairs of foam on Ebay for my next repair .

      Delete
  3. Your replacement pads look to be black. Your restored headphones appear to have yellow pads. Am I missing something?

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    Replies
    1. Hi Charles - no, you're not missing anything.

      The black earpads are held to the headphones via the original yellow cloth covers. These yellow cloth covers are simply used around the black foam pads to hold them against the earpiece. They're not pads as such.

      Hope this has answered your question.

      Delete
  4. Nice- needs more work though - tranducer cover removal, replace rear (gold) foam with cheap foam covers from ebay (needs trimming)- this gold foam is dead and affects treble output if not replaced- johnnykojic@hotmail.com

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    Replies
    1. IGNORE THIS ADVICE-GLUE TURNED TO GOO AFTER 25 YEARS- IT GLUES THE OUTER BASKET TO THE COIL WIRES- IF YOU REMOVE IT WILL RIP THE WIRES- SORRY MY MISTAKE

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  5. Hi Johnny

    Thanks for your comment. Do you have any examples of the replacements you suggest for the gold foam? I've looked on the 'bay but not found anything suitable.

    Thanks

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  6. IGNORE MY COMMENT-GLUE INSIDE TURNS TO GOO ANS STICKS THE COIL WIRES TO TO TRANSDUCER COVER- IF ITS REMOVES THE WIRE WILL RIP- SORRY MY MISTAKE- NEED TO FIND ANOTHER WAY?

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    Replies
    1. I do hope you've not damaged your HD420's finding this out....

      For me, I'm happy with mine as they are now. Not sure I want to change the gold coloured foam in the earpieces as this would change the look of the phones. I do need to think about how I might clean the foam though and get rid of the green staining....

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  7. I had no idea the headphones could be refurbished until I saw this article. New foam pads fitted yesterday - odd that they're not simple disks I thought. Re the gold (outer) foam, mine have one side gold and one side green tarnish. It would be nice if it could be changed too, but is that possible? Thanks very miuch for the site and photos.

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    1. Hi

      Thank you for your comments. I still can't clean my outer (gold) foam. I too have green tarnish on the foam but dare not try any abrasive cleaning as the foam is just too fragile. For the moment I have left them discoloured, as it doesn't seem to affect the sound.

      Hope you enjoy listening on these old phones as much as I do!

      Martin

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    2. Having the same issue with my 420's. These articles are very helpful. Can't believe I've had these for almost 40 years. Good products last, right? :)

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  8. Brilliant repair . I'm not the only one who likes these old cans it seems . I have some HD 400s which I bought in 1978 , and for the same sound quality reasons and lightweight construction have never changed them . I have managed to replace the foam covers and an open circuit driver by the purchase of another pair from eBay .

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  9. I found some of these that my dad used to have but the left side doesn't work, any suggestions for fixing this or would it be better to just chuck them?

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    Replies
    1. You could maybe try looking for another pair on eBay and combining the two to make one fully working one?

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  10. Thanks Martin. I got 2 pairs of pads for £3.25 incl. postage from eBay and fitted one pair this afternoon using your advice. They are now comfortable again and, after clearing out all of the decomposed old pad material, which had turned into a dark oily sludge, they now sound a lot better too. The ones I bought were advertised as being suitable for HD433/HD44II/HD420SL, but they fitted my non-SL HD 420 phones just fine. Thanks again.

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  11. Thank you Martin. Now I have made these comfortable again I will convert to Bluetooth with a TaoTronics TT-BA07 Bluetooth, I have already purchased. These will be my on the road phones; got to like wireless phones with my Sennheiser RS180, but those with base unit, too cumbersome for travelling.

    Alan

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  12. Hi I want to replace the gold sponge on the outside its gone green is there a way to replace this .Its got holes I think in it .Thank you Ross

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    1. Hi Ross

      I've not found a safe way of replacing this - or indeed cleaning the original foam. I did try gentle cleaning and the gold foam just disintegrated.

      If you find out how, please let us know!!

      Thanks

      Delete

  13. Just after I put this here I got some light black foam very
    thin I had and ripped little bits of it and pushed it in to the holes where I could see the white .I then found a gold permenant marker pen and changed the colour to gold . .one has to be carful doing this maybe best to change the foam to gold before pushing in with gentle ease .This will have to do for now ok . Let us know if you find better than this thank you Ross

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  14. Genius thank you :) My trusty 35 year old HD420s are restored from unlistenable to what I had remembered as their former excellent sound quality. Shame I didn't see this before shelling out on rather disappointing B&O H2s last year.

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  15. so pleased to discover the 'official' source of this information :-) here is how i repaired my HD475s:

    (1) i used a vacuum cleaner to remove the rotting foam clinging to the transducer. this technique is fairly safe if you limit suction by opening the valve on the handle.

    (2) pads for Grado's SR series cost very little at eBay. i bought ring-shaped ones thinking it would be easier to fit them neatly inside my HD475's oval covers. my Grado transducers are not covered by foam, so i decided that this isn't important.

    (3) regretting my choice of pads (it would have been easy to remove excess material), i put toilet tissue between the covers and pads to reduce treble response.

    Thanks to everyone who contributed, especially Martin. you're the best!

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  16. Thanks for the pictures. It was helpful. You can remove the round cover (with the cotton padding) from the transducer by gently pushing on 4 tabs which are barely visible from the outside of the transducer.
    After that is removed the gold foam can be accessed. Mine is also disintegrated. I found a material at a hobby store which is suitable as foam for dampening. I used it also to replace the foam on the HD414SL model. I cut them to size and used two layers. If I find out the name of the material I will advise.

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  17. For the circular dampening material I am using two layers of felt cut to size. For the HD414SL I used yellow but for the HD420 I plan to use a color closest to gold (that I can find) and use a lightly sprayed layer of gold paint to keep it looking original.

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  18. Found a pair of these headphones and i did the same.Only problem i have now is that I have no idea if they work; I know they are 600 ohm. I have been unable to hear anything while plugged in to phone or PC. What have you used to drive them?

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  19. Scratch my last couple of comments. After taking apart the cover to the voice coil I realize that there are some very fine wires that may be held in place with some goo. The goo can stick to the part being removed and jeopardizing the status of the wires. This is not a user serviceable item.

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  20. I know these are 600 Ohm but will they produce sound with phone or pc. I dont know if my pair are broken or just lack power.

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    1. Hi

      They will produce sound from a PC or smartphone but the sound will not be very loud. Most portable devices (such as smartphones and laptops) use a supply voltage of between 3 and 5 volts and that means the signal voltage at the output of the device is low, but they can deliver high current with normal low-impedance headphones and the sound will be fine. However, if you plug a high-impedance headphone such as the Sennheisers into a portable device the voltage and current will be low, so the headphone won't play loudly at all, and dynamics will be reduced.

      You can improve things by using a headphone amplifier. I use an older version of the Fiio E11 (https://amzn.to/2wNQOG9) and that drives the Sennheisers very well.

      Hope this helps.

      Martin

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  21. There's no sound coming from the left channel of my HD420 headphones. Do you have any ideas how to fix/repair this problem? This issue is not associated with my stereo equipment. Thank you.

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  22. Most likely the cable is not making contact. Usually just pushing the connector in place will remedy it. If the cable is old you can get replacement cables from Sennheiser.

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  23. Push the cable connection in as far as it will go as one of mine came loose and I ended up with the same symptom.

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  24. Any ideas how to restore the plastic and make it look fresh and shiny again, also I think I will attempt replacing the outer gold foam since mine is very torn, Ill try to solder the wires back together if they break. May also try to just remove the foam completely or find something to cover it.

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  25. Well thank you so much. Just found your blog and had been looking for earpads for my HD420s for years. Now renovated for very little outlay. I had forgotten how good these sound. Also I found an old pair of HD40s and have found some earpads to fit them. Less than £4.00 for both sets.:-)

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  26. Thanks for this useful article, I've now successfully replaced the pads in my HD420SLs. FWIW I fitted my pads in a slightly different way. In your image HD420-5.jpg you can see a ring of transparent plastic (though in mine it was black). I tucked my pads through the hole in that so that they were fully in contact with the yellow material across the whole diameter. I've no idea how they are supposed to be, but that seemed more logical to me! I suspect it also makes refitting back on to the transducer a bit easier. The end of a 12" ruler (used like a tyre lever) helped with that task.

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  27. I have multiple different Sennheiser models and I find that the HD420SL are a duller sounding headphone. Still very useful if you want to reduce ear fatigue.

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  28. The inner headband on my HD-420's (that is adjustable) has broken. Had them for 35+ years an love them. I'm trying to find a replacement. I've already replaced the inner foam and outer pads and they are perfect, but without the over the head plastic, they're worthless. Currently I'm using paper clamps to keep them together... i look like an alien when using them. Any help in locating the headband replacement is appreciated.

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    1. Is that the plastic head band the part that go s over the head I have spare one if it is for the HD420
      let me know and I can send .Are you in The UK .My Name is Ross I live in the south of England

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    2. I have a spare head band is this what you want for the HD-420

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  29. Hi, Just to say I agree with your comments on the HD420. I bought my pair in 1981 and last year did the same renovation as you - the original foam pads had compacted, making the sound dull, the repair totally restored their sound (taking into account that my ears are probably not as good now!). Last year I bought a pair of Sennheiser HD569s as my wife found the leakage of sound from the HD420s annoying. I keep going back to the HD2420s! Anyone thinking of doing the repair - it's well worth it and easy to do - with care. Peter

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  30. Very helpful article. Many thanks. It helped a lot. I replaced the worn out pads on my 40-year-old HD420s with original Sennheiser 80mm pads (article code 053241 - from Audio Sanctuary for about £4). Like "Anonymous" (2 May 2020) I also tucked the pads through the hole in the black plastic so that they were fully in contact with the yellow material that is in contact with the ear. Refitting was simple with the help of a rounded spoon handle. Result: good as new and sound great.

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  31. This is wonderful. My fatger was bass player for Doctors of Madness and TV Smiths Explorers. Sadly he dies a few years ago. I now have his head phones! I am going to restore them. Still sound great. I can hear what he did.
    I need advice on replacing the wires too because they make a subtle clicking sound if moved or touched. Can anyone advise? Do they unlpug without breaking at the yellow and red/left and right cable ends?

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  32. Amazing! I've just restored my original 1970's HD420 headphones and this procedure worked a treat. Thank you so much for posting.

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  33. I just fixed my HD420 headphones today, now they're almost like new ;)
    Thanks for the detailed fix instructions.

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  34. Thanks for the advice, restored for less than the cost of a pint of ale!
    Headphones are working great now.
    Richard

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  35. I am lucky enough to have 2 pairs of these headphones but one of them has the strap of the headband missing, do you know where I can get a replacement?
    Richard

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    Replies
    1. I think I have a spare headband

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  36. João Fortunato9 May 2022 at 14:13

    Good afternoon
    are they as good as the sennheiser px 100?

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  37. Fantastic - sounding now as they did in the 70’s. Thank you!

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  38. Dazz I to have the Sennheiser HD 420 headphones from the 70s, love them great sound and still working well, but needs new pads.
    Thanks for the video demonstration and I will repair these much loved headphones.

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