[pox67]

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!

 

[duncan1]

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.

 

[pox67]

"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.

 

[nikongod]

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. 

 

[duncan1]

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.

 

[wakibaki]

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

 

[pox67]

Quote:

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.
 
Quote:

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

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

 

[duncan1]

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.

 

[jfunk]

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
 

 

[pox67]

Quote:

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.

 

[pox67]

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!
 

 
 
 

 

 

 

 

 

[deppard]

Hello from a new member ! (but long-time lurker).
 
Sorry to dig up an old thread on my first post, but the issue is directly related to this thread (only info I found on the net).
 
I am not much of a headphone junkie but do own a few of them, while I use the sennies HD-25c-ii constantly for work. I had the same problem many others faced, sound cutting out on both sides. Two days ago I decided I had enough, opened them up and tried to squeeze the springs in the connection point, while also putting a tiny bit of solder on the cable connectors as well. 1 cup was finished and fixed, but I discovered (to my horror) that I have snapped one of the voice coil wires on the left cup.
 
I tried to solder that hair-thin cable but all I managed to do was melt down a significant part of it. So, the fix explained above (where you solder the wire directly to the spring) does not apply anymore ! The two parts of the cut-out cable are of enough length to meet (just enough), but how am I supposed to solder them ? Is it aluminum or copper ? I definitely don't have the skill, but could I ask someone to tackle it ? I wonder if it's possible at all..
 
A new earcup costs almost as much as the headphones, so it's out of the question. I e-mailed sennheiser but they haven't got back to me. Have I really ruined my pair just like that?
 
Thank you for your time in reading this.

 

[jfunk]

   
 
I tried to solder that hair-thin cable but all I managed to do was melt down a significant part of it. So, the fix explained above (where you solder the wire directly to the spring) does not apply anymore ! The two parts of the cut-out cable are of enough length to meet (just enough), but how am I supposed to solder them ? Is it aluminum or copper ? I definitely don't have the skill, but could I ask someone to tackle it ? I wonder if it's possible at all..
 
 

Hi Deppard,
                I have done quite a few of these operations - the voice coil is aluminium and it is best to use a temperature controlled solering iron and some low temperature aluminium solder... That way you don't melt the voice coil. Sennheiser do offer fixed priced repairs on the HD25 which costs a little less than replacing the earcup or if you are feeling entrepreneurial you could buy a cheapish pair off ebay and then re-sell the parts you don't need separately 
J 

 

[pox67]

Hey Deppard, sorry to hear about your headphones. I did repair mine and have been using them ever since. I think they sound even better with a solid connection.
 
First of all don't use normal solder as the voice coils are aluminium and hair thin. I bought some stuff from ebay called: ALUSOL ALU-SOL soldering wire for Aluminium aluminum & most metals 50g 0.91mm.
 
This is what I did:
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.
 
Good luck!

 

[deppard]

Hey there jfunk, thanks for replying. I remember your work on these headphones (djf member since 2003!).
 
Assuming I have a temp controlled iron and low temp aluminium solder, is it relatively straightforward to connect the voice coil wire ? It's too thin.. I tried to force a contact between the cut parts to see if any sound passed through to no avail. 
 
I assume sennheiser will do a fix for ~100 euros and, as the new cup costs ~120, I am even considering getting a new pair for 165 ! Used + postage to SE eu is not that much less I;m afraid.