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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.  :)

22 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 .

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  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.

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  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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    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

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  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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