Wednesday, January 7, 2009

How to Fix Broken Speakers

The reason that I created this site is because I wanted to explain how to fix broken speakers online for beginners like you. Some knowledge about the inner workings of a loudspeaker will show that its not that complicated. There are several types of devices that produce sound but they all do the same thing which is move air. Later I'll get into the differences but for now we'll concentrate on the most common type which is the cone piston driven by a wire coil in a magnetic field. This is also the easiest to understand and repair.
Since this is all about speakers online for beginners you will want to know how speakers work, why they stop working and how to fix broken speakers.
I don't want to bore you with too much repetition but I want to make sure you get the overall picture. There are only a few moving parts and these are the ones that may need fixing. If the speaker received an extremely violent hit like being dropped off a truck or falling from a high place, the magnetic structure may have shifted out of position.
Many speakers have the magnet attached with bolts but some use only glue. If misalignment occurs the magnet would have to be demagetized with a very expensive, large and dangerous machine before it could be reconed with new coil, spider, cone, lead wires and surround. (I will explain these terms in detail later) Then it would be remagnetized with the same machine. Speaker manufacturers are about the only ones who would have these machines other than factories that make magnets. Some large recone shops may have them.
These pages will document and explain how to fix speakers that have the magnetic assembly and frame intact.
I have been a pro soundman for many years and a musician for even longer.
Over the years I have fixed many broken speakers. I worked for a sound company where I was responsible for trouble shooting loudspeaker problems. Lots of times we had blown speakers that had been overdriven due to operator error. I would generally send these out to a recone shop and put a spare in the box. Sometimes I could fix them if the problem was due to a visable glue joint which had come unglued. This can happen with the spider, dustcap and sometimes the surround. High frequency horn drivers are pretty easy to fix becuase you just have to replace the diaphram assembly, which is the only moving part.
As far as my own personal audio equipment goes, many times I simply couldn't afford to buy new speakers or send them out to be reconed, so I had to try and fix them myself.
Very often it is actually not worth the time and effort to fix them and you're better off just buying new ones. The rule of thumb is: if it has a stamped steel frame don't bother to recone the speaker. If it has a cast steel or aluminum frame it's probably worth fixing.
In some cases, the problem is just a question of applying some glue in the right places. Like when the spider comes partly unglued. Or when there's a small hole in the cone.
Other times, when the voice coil is burned out, the entire speaker cone, voice coil, spider and surround must be replaced. That's what is involved in a recone.
Many modern speakers have foam surrounds that rot with age and exposure to sunlight. There are several companies that sell kits to repair foam surrounds yourself. Look around for good deals because the prices can vary over a wide range. Try Weber. They make their own speakers and have lots of extra parts for sale at very good prices. Also tools. And they make great guitar amps.
For some reason, people like to poke their fingers into unprotected speakers and sometimes poke holes in the cone or surrounds. If there is a metal dust cap over the center of the speaker it will dent easily. You can sometimes pull it out with some tape pushed onto the dent and a swift tug (be careful!).
For an example of a repair job with photos check out my page about a pair of JBL D130F's that I successfully reconed. JBL D130F Recone Job
Go here to see how I rebuilt a blown 12 inch EV speaker into something different.
EV Speaker Custom Rebuild The only original parts left were the coil (which was not burned) and the frame. The photo at the top of this page is that speaker.
I fixed another EV 1000 watt 15 inch (EVX 150) that had the lead wire break off at the coil. It was actually a ribbon or flat wire. I was able to solder it back on and then coated it with epoxy. This fix involve very carefully cutting off the dust cap (without damaging the cone). The cone was the molded type which is very thick so I got away with it. I glued the old dustcap back on after the repair and was using the speaker for bass guitar gigs.
1000 watt EV EVX150 voice coil
There are other examples at my other blog. Check out Fix a Loudspeaker and Big Speakers Big Problem

Scott midrange re-edged with tissue paper and rubber cement
Here's a midrange in a Scott hi-fi loudspeaker that I repaired with tissue paper and rubber cement.

In this case it was the surround that needed repair but paper cones can be fixed this way as well.

I want to show people how to fix speakers online.
Also check post about spiders and voice coils.

broken voice coil wire
 The bottom couple of rows of wire came off the coil former and the wire got chopped.
soldered voice coil
Note that there are two layers deep of round wire.

I was able to solder it back together.
Then glue it with super glue(cyanoacrylate)
Its from a high power 18 inch subwoofer.
Then I glued the whole thing back together.

disassembled speaker

I was lucky that the spider came apart without being ruined.  I used acetone to dissolve the adhesive.