Help needed with faulty speaker!

Hi, my audio knowledge is limited so please be patient...
I've just built cabinets for my KEF CR160f's (fullrange that pre dates UniQ I think).
They were working fine when I tested them. I then took them out to paint the cabs, and when I resinstalled one was dead.
After minor investigations it looks like the little unit on the side of the driver has blown. I don't know what this thing is, it has a capacitor on top (well, a little blue cylinder that says ALCAP), and below this is a plastic case with something pink inside. The +ve wire goes through this unit.
When I bypass all this and go straight to the driver sound comes out perfectly. I could keep it like this but I assume it's there for a reason.
So, if you're still with me I have two questions. Firstly, what is the faulty unit and secondly how do i fix it?
I have no idea how this fault occured, one minute it was working next it wasn't, I'm sure I didn't overdrive them and all electronics seem fine otherwise.
Any help seriously appreciated.

 

I would suggest contacting KEF's service department! The well-established hi-fi companies are usually very good at helping with problems like yours.

 

Right, thanks. will try them.