ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hello Beoworld!
I bought a couple of second hand S45-2's with completely frozen subs. Not knowing anything whatsoever about the insides of speakers, and finding it daunting at first, I prevailed. I want to add this thread to illustrate the process again and let the world of Beovox lovers that this is a easy repair. With the help of many on the beoworld site. I hope this is helpful. I'm following Craig's method with a couple of helpful reassuring remarks from Martin. Thank you both!
Here's the progress.
Bob
I started out with ruffed up speakers with two frozen woofers. The hardware though was in excellent shape.
The Problem: Frozen woofers!
If you plug your speakers in and you get only treble, open your speaker up and see if the woofer is moving. It probably isn't and there is hardly any sound coming from it. The problem is that the backside of the woofer has dislocated, ensnaring the voice coil and preventing it from moving. A simple mechanical problem due to glue failure. No movement, no sound.
The fix
Now luckily there is a fix! Reglueing them! It's a well documented problem that seems to occur a lot to the S45-2's. It takes two days:
First of All
I didn't understand how a woofer works. Here's a great animation explaining it in a minute. You can see all the parts you're going to encounter. And it offers the basic terminalogy you need to follow the instructions without too much stress.
Then the actual repairing, in steps:
1 Removing the woofer
First I unscrewed the woofers and soldered the connectors loose.
2 Removing the magnet, core and backplate
On the backside of the steel frame, three large metal elements are attached to the woofer frame. Those are:
The core is glued to the center of the backplate. These are then glued together to the ringmagnet. The ringmagnet is glued to the woofer chassis. What has happend is that the adhesive has failed and these parts have shifted. So you need to get these parts off the frame and reglue them. These are the three parts you need to fix up first:
3 Cleaning off the glue residues
These metal parts are glued together with strong glue! So you need sandpaper to clean them up. This is important so you can glue them together properly: with even smooth surfaces.
4 Ruffing the surface up
After sanding them clean, I used pretty rough sandpaper to roughen all the parts up, seeing to it that the glue has a better chance of grabbing onto the parts. Important though is to rub the parts clean very well. You don't want metal dust in those grooves. The glue won't stick if you do. This was the result:
5 reglueing Step 1: The core to the backplate
For reglueing, I used epoxy glue, Gorilla glue. It's very easy to use! Here is a short and clear demonstration
So first of all you need to glue the core to the backplate. I used the ring magnets to center the core. I didn't glue them! You need to get the core on the backplate, in the right place within 5 minutes, put a clamp on it and let it cure for 24 hours.
6 In the meantime, cleaning the back of the frame
So the back of the frame needs some cleaning too. At first, it should look something like this:
Use sandpaper to remove all the old epoxy. Watch out for the voice coil (the red thing - it's really fragile). There is no need to get close to the coil. The ring magnet, which you will be glueing around it, sits at a distance from the coil. After cleaning it should look something like:
6 Regueing step 2: The magnet to the backside of the chassis
So now the ring magnet needs to be glued to the backside (the previous photo). For this too I used the Gorlla epoxy. It needs to cure for 24 hours. Be sure to center it around the coil as precise as you can. I used a simple ruler to do so. I didn't use a clamp or anything, just the magnetic force between the chassis and the magnet. After glueing it should look something like:
6 In the meantime, so everything is curing for 24 hours.
That gives you some satisfied time to think. As I was feeling good about myself, being thorough, careful and precise, I decided to sand the speaker cabinets and wax them. This old stuff is made from proper wood and aluminium so if you fix them up they look good as new! Really worth it. Sand in the direction of the wood! You can also sand the aluminium edges with fine sandpaper.
7 The next day. Don't be unpatient! ;)
8 Reglueing step 3, the final step! Glueing the backplate and core to the magnet.
8-0 Removing the dustcap
So what you're going to be doing next is glueing the backplate+core to the magnet+chassis. The most important step is: you need to center the core in the coil. To be able to see what you're doing, you need to remove the dustcap from the front. I used a hairdrying to warm the glue and the very gently and patiently pried the edges of the dustcap from the speaker with a precision knife. It took be about 40 minutes a woofer to do so. You don't need to completely take the dustcap off. Don't mind the piece of paper sticking out.
Final Glueing
So now you need to glue the backplate+core, to the magnet. Before you do I want to say why the woofer got stuck in the first place. So the glue failed somewhere and that caused the backplate+core, or just the core, to get sucked towards the ringmagnet, ensnaring the coil. So when you reglue you need to be sure that the coil can move freely. This is pretty precise work but doable. I did it like this first:
8-1 What you DON'T WANT to do
You need to see to it that the core doesn't ensnare the coil, so there is room in between, evenly around the core. I took a piece of paper and rapped the coil. However, when I raised the magnet+woofer over the paper and down towards the core+backplate, the paper got so stuck that I couldn't get it out! You really don't want that to happen.
8-1 What you WANT to do:
Put the backplate+core in a vice (as photo above). Cover the backplate around the coil with epoxy. Don't go too close to the core. There is no need, for the ringmagnet goes a ways around the core, and you might get yourself in the situation that something gets glued in there that you don't want glued. Now instead of the paper cilinder use strips that you can easily pull out. Once everything is centered, let it cure for 24 hours.
- in progress, will post more tomorrow!
I love watching someone else going through this....I tried the thin paper/mylar strips approach myself, it will work but I found it hard going. I started to think about how a manufacturer would assemble a speaker and decided he wouldn't use strips of paper, he must surely use a jig of some description....a plastic pipe of suitable diameter and wall thickness (schedule) with two sets of holes drilled and tapped was my solution.....its so much easier, keep the pictures and progress coming Bob......
Craig