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Sennheiser HD25-1 voice coil repair suggestions

post #1 of 11
Thread Starter 

My Sennheiser HD25-1 ii have developed the problem where the speaker connectors need to be jiggled or plugged in a few times to get a good connection. This was becoming so bad that in the end I couldn't even get the left headphone working properly at all.

 

I decided to open them up to check if I could tighten the spring inside or maybe just solder the wires in and discard the plug altogether.

 

Well now the soldering has become a must as I broke one of the voice coil wires..very good explanation of what has happened here:

http://www.head-fi.org/forums/threads/add/forumId/6

 

So any suggestions for soldering the voice coil wire in?

Seems the voice coil is aluminium...which might mean soldering isn't even an option...

 

Any help greatly appreciated!

post #2 of 11

You have got yourself into some trouble. I have repaired this type of break in the voice coil in many loudspeakers. but it isn't easy.the copper wire of the voice coil will be held in by varnish. If the  break is on the actual voice coil then using a fine needle scrape off the varnish and then using the needle SLOWLY pries off the broken end so that it is loose from the coil . Then get a small soldering iron and burn off the varnish from the broken end using the soldering iron FINELY coat the broken end with solder. Then add a small piece  of fine copper wire to the broken end and then solder it to the same place the original  unbroken voice coil wire was soldered too. You need a steady hand otherwise buy a new pair.

post #3 of 11
Thread Starter 

"Luckily" the break is where the voice coil wire joins the the cable connector. So I have about 1.5cm of wire to play. Other problem is it is aluminium wire and thinner than a human hair...

I have had some tips from JFunk at Custom Cans in the UK and will try a repair this weekend.

post #4 of 11

Be careful with voicecoil wires. In addition to being physically brittle (aluminum ones in particular) they are known to melt/vaporize from the heat from soldering. 

 

More than 99.9% of the time the failure is in the user-replaceable cable. If you do manage to actually fix the driver expect to buy a new cable. You can check your cable by removing it and probing with a multimeter. 

post #5 of 11

If it really is aluminum wire its not going to solder. You can cover it inside a blob of solder but it will have a resistance to the blob of solder   you cant solder aluminum without special  equipment. Aluminum is very brittle and doesn't like movement. Had aluminum cables  in British Telecoms many years ago .It didn't last very long when large lorries gave out heavy vibration and the cables   underground shattered. They reverted back to copper cable.It also oxidizes a lot quicker than copper or even silver.

post #6 of 11

Multicore make a cored solder called Alu-Sol for aluminium.

 

Unfortunately I don't know where you can get it in small quantities, Newark sell a big roll that costs $82. I have a small quantity that I bought years ago from Maplin in the UK, but they don't carry it any more.

 

It does, however, form a bond with aluminium and even some stainless steel, and once you've tinned the item with Alu-Sol you can solder to it with regular solder.

 

w

 

Oh, here you go.....

 

http://www.ebay.co.uk/itm/ALUSOL-ALU-SOL-soldering-wire-for-Aluminium-aluminum-most-metals-50g-0-91mm-/271259146923?pt=UK_BOI_Metalworking_Milling_Welding_Metalworking_Supplies_ET&hash=item3f284e1aab


Edited by wakibaki - 8/27/13 at 3:57pm
post #7 of 11
Thread Starter 
Quote:
Originally Posted by nikongod View Post

More than 99.9% of the time the failure is in the user-replaceable cable. If you do manage to actually fix the driver expect to buy a new cable. You can check your cable by removing it and probing with a multimeter. 

 

It is definitely not the cable, it was the problem reported on in the link in the original post. The speaker/cable connector that Sennheiser uses develops a fault where it doesn't make a good connection. There are various "fixes" but none are for sure. I decided to solder the joint without doing much research, so here I am. The headphones were unusable anyway as the speaker/cable connection was so bad only a faint sound came through.

 

Awesome, thanks wakibaki. I just ordered some. Will take a week or two to get Australia.

post #8 of 11

Thanks for the information --Wakibaki- didnt know that about the aluminium solder and me a member of Maplins since it started in the 70s with its magazine. I dont think there were any shops then all via postal services. Unless there was a main shop in London.

post #9 of 11

That aluminium solder looks handy. Just to spur you on... It is definitely possible. Here is a pic of a voice coil wire repair on a HD25 - the wire has been soldered directly to the spring rather than joining the two parts of the wire. You can see the broken part of the wire still attached to gold stud type thing underneath

 

post #10 of 11
Thread Starter 
Quote:
Originally Posted by jfunk View Post

That aluminium solder looks handy. Just to spur you on... It is definitely possible. Here is a pic of a voice coil wire repair on a HD25 - the wire has been soldered directly to the spring rather than joining the two parts of the wire. You can see the broken part of the wire still attached to gold stud type thing underneath

 

 

 

Thanks for the pic jfunk, that is a good idea soldering to the spring post.

 

I am in two minds of what to do as I have already modified the speaker cable on my headphones:

http://www.head-fi.org/t/568795/bluetooth-sennheiser-hd25-1-ii-my-search-for-decent-bluetooth-headphones

I have actually gone back to corded even for commuting as the Bluetooth was too much of a dip in sound quality. I do still like being able to swap in a longer/shorter/curled cable at whim though. (Ugly black jack later replaced with a locking silver one: http://www.cseonline.com.au/35LJNAUS-3.5mm-Inline-Jack.html).

1. Cut the connector off and pass the cable  wires through and solder with voice coil wire. Maybe using the spring post as a meeting point/support.

2. Soldering the connector ends to the springs and then the voice coil wire to the spring post.

 

My preference is #1.

post #11 of 11
Thread Starter 

I am back and with success!

 

I wouldn't undertake this unless your HD25-1's are completely shot in the connector department. I am an OKish solderer and only do it for necessity, mostly remote control cars/planes.

If you are an good solderer please don't look at the solder picture, it is a disgrace. The other one was slightly better but it is terrible as well. On the plus side it all works and no one will ever see it again...

 

It was tough soldering those little wires and I had to solder each one a few times as either the voice coil wire would snap or the solder would give. It was much easier working with the AluSol than regular solder but it was brittle.

 

I decided the best course of action was to completely gut the current connecting mechanism. I pulled out the spring and brass posts. Then drilled a bigger hole to put through the headphone cable and removed the inner plastic separator. 


I split the cable and used a mini butane torch to burn off the insulation on the wire strands. Be very careful of doing this on the aluminium voice coil wires as more than a fraction of a second and they will disintegrate. I found that the red insulation on the voice coil wires actually comes off in the soldering process.

I tinned the speaker cable wires and then set the voice coil wires to be pushing against the solder blob on the speaker wire with natural spring.
Then simply melting the solder blob had the voice coil wire sink in to it.

 

I put a cable tie around the end of the speaker wire so it wouldn't get pulled though the hole in the casing.

 

Then it was just a matter of fitting it all back together.

 

How do they sound? Great but it has been so long since I listened to them I can't tell any difference and in the mean time I picked up some Beyerdynamic DT1350 to console me in case it didn't work.

 

Now I have two fantastic sets of portable headphones :)

 

Thanks everyone for the help and suggestions!

 

 

 

 

 

 

 

 

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