Speaker repair (and phase plugs)

[Graeme]

Just collected a pair of goodmans twin axiette 8's, the ones advertised on here.

Unfortunately, when i got there the seller had had time to test them and one doesnt work.

Shame, but we came to an arrangement and a deal was done so no biggie.

So, im now on the look out for another.

In the mean time, can they be fixed? Theres no continuity between the terminals, the wires to the cone have no continuity, i can get to the inner terminals too, underneath the 'tweeter' cone and theres no continuity there either.

I must confess i dont actually have any idea how speakers are put together, or even exactly how they work , so, can anyone point me at some basic diagrams? What are the chances of being able to disassemble so i can get in to try and fix the problem? Whats the problem even likely to be?

Any ideas folks?

As a last resort, are there any 'pro's' who can fix this sort of thing?

[steve s]

remember when you check the wires from the voice coils that they are coated i fine blade gently scraped along should expose the alloy or copper..the usual place for it to break is at that cone connection

steve

[Graeme]

Ok, ill have a better look.

They worked when they were stored apparantly so i'd guess a break somewhere ratehr than burnt out.

The cones move freely with no noise.

The twin axiettes have parasitic tweeters so access isnt great. On the other hand i wouldnt be able to get to the wire at all if they didnt have them.

[Graeme]

Right. Looking from the front of the driver, i can get down between the cone and the 'tweeter' cone. I can see the 2 wires running down into the center of the speaker. I assume these are both ends of the voice coil?

I can get continuity between the thin wire and the speaker terminal, on both sides, but no continuity between the 2 thin wires.

I assume the wire has broken away from the voice coil, is there any way to get at this?

[Graeme]

I found this,
http://electronics.howstuffworks.com/speaker5.htm
Just a basic about how speakers are put together.

I dont think i have anything to loose really, may as well try and take it apart and see what happens.

If i can get to the coil......

[Graeme]

Having gotten annoyed with trying to sort my pre amp i thought i'd spend this evenings efforts doing something else so turned my knife on the broken axiette.

I figured it cant be that hard to fix, and nothign to loose so.....

I cut/pulled off the thick (card?) surround so i could get to the suspensions/basket mounting.

I then pulled the card back off, unsoldered the leads to the terminals and cut the suspension free from the basket.

Undo the 3 magnet bolts and pulled the whole magnet/cone assembly out.

Then i ran a knife under the spider so i could remove the cone from the magnet.

The voice coil is now exposed.

I cleaned the enamel of the led out wires and checked continuity. Coil was fine but one led out wire is obviously broken.

I got a needle and made a new hole next to the old voice coil lead out wire and fed a thin wire (the same guage as the coil wire) into the cone.

I then made another hole where the lead out wire goes through the cone and fed another wire through.

I now have 2 wires in the cone. Twisted and soldered these together, solderd one end to the lead out wire and glued the new hole through the cone.
I ran some thinned glue down the wire inside the cone so its stuck to teh surface the same as the old one was.

Now i just need to join the new wire to the coil. I cut the end of the coil wire keeping as much as possible, twisted the old and new wires together and soldered them together.

I glues the coil back to the inner tube with super glue so its all nice and flush and doesnt foul as the cone moves.

Checked again and hurrah, continuity again

Checked resistance and its 12.4, exactly the same as the working driver.

Just letting things set before i glue the cone back into the basket and the spider back onto the magnet.

Small, delicate, fiddly work but not that hard really.

Just hope it actually works when it back in one piece, should do though.

Any recomendations on glue to stick the suspension back? The old glue seemed quite rubbery, evo-stick style. Just some kind of rubber glue?

[richardcooper2k]

well done !

[Graeme]

Ive glued it all back together, i think its all centered properly but its a little hard to tell.

It would have been easy if i hadnt had to remove the spider.

Pushing the cone in and out you can sometimes hear the voice coil catch, but its the same on the working driver too. It depends how you move the driver. Without being able to put equal pressure all around the cone when you move it you cant test properly.

Anyhow, ill re-wire my pre-amp, get that working properly then test the speakers. Worst comes to the worst ill have to take it apart agian

[Graeme]

Another thing, whats the deal with phase plugs?

The twin axiettes have a silk dust cap, if i need to recenter the driver ill remove the dust cap and shim the voice coil.

However, this will leave me with no dust cap as i doubt ill get it out in one piece.

Replacing the dust caps with phase plugs seems the obvious answer, but can they ne detrimental or is it a case of they either improve things or they dont?

I guess i'd have to make some but ill take some measurements and see if any are available in the right size.

Anyone in the uk sell them?

[Graeme]

It works

Sounds nice too, although its hard to tell as i only hooked up the repaired one and left the otehr channel playing my other speakers.

Ill put the other back in its box, have a good listen then start playing with woodwork again.