PDA

View Full Version : 125a woofer 'rattles'



jay
02-02-2005, 09:05 AM
Hi guys,

A couple of days ago I was given a nice pair of L26's that look terrific, but need foam surrounds.

Naturally, it was only AFTER I did the surround job that I discovered that one of the 125A woofers has a light metallic rattle. :biting: It's an obvious rattle, either with the woofer installed, or holding it up and shaking it. In addition, there a staticy, scraping sound when powering up the amp. My foam job was accurate, so it isn't that.

This can't be good. Is this a fixable fault? Can I remove the spider and re-glue something under it? :blink:

Jay

Robh3606
02-02-2005, 09:13 AM
I don't know that doesn't sound good maybe a loose winding/s are the leads to the VC loose or hitting?? I had a 129H where the tinsel leads go to a terminal lugs screwed to the frame. One of the screws was loose. Sounded the same, it rattled, was funny with power applied but when I tightened the screw it was fine. I think the 125's have riveted keyed spades but it could hurt to see if they are nice and solid. Hope it's not the coil:barf: You measure DCR??


Rob:)

jay
02-02-2005, 10:37 AM
Hi Robh3606, and thanks for the pointers.

You're correct that the 125a has the tinsel terminal thingy riveted to the basket. Anyway, the wires are safely away from the cone. Nice idea though!

How is DCR measured?

Jay

Robh3606
02-02-2005, 12:11 PM
You have an Ohm meter ??? Just measure the resistance across the two input terminals to the driver. Measure the good one too. They should be reasonably close. I don't do this for a living but I would quess shorted turns would lower it and overheated would run way high. The PRO's will jump in soon enough. There are DCR ranges for the driver available somewhere.

Rob:)

Mr. Widget
02-02-2005, 12:58 PM
From his description of the problem I would guess that if indeed the foam job isn't the problem and the cone is properly centered, then the voice coil is probably out of round. :(


Widget

pelly3s
02-02-2005, 03:46 PM
Well there could be a peice of metal floating around the gap like maybe a small chip off the maginet. does the 125 have a ring on the bottom of the center pole because i have seen them come loose on many drivers causing a rattle. I would go with a peice of metal in the gap though. When the recone was done was the dust cap removed?

jay
02-02-2005, 06:51 PM
Hi guys

The dust cap wasn't removed for refoaming, and the rattle defintely has a 'metallic' character.

It beginning to sound more and more like there's nothing to lose by taking the whole schmere apart. :(
Thanks a lot for the fine tips!

GordonW
02-02-2005, 08:17 PM
I've had cases, where 125As and 127Hs had been played with decayed foam, and the bottom of the voice coil became "mushroomed" from bottoming out. In these cases, I've managed to cut out the spider, unsolder the leads from the terminals, lift out the cone assembly, and carefully trim off (with a VERY SHARP Exacto knife or equivalent) the bent part of the former at the bottom of the coil (below the winding). Then, I remove the old spider, replacing it with a new one, carefully remove the dustcap, shim the voice coil and re-glue the assembly into the basket. At this time, I put in a new surround. Once it's all cured, remove the shim and re-glue the dustcap...

It's not a job for a "novice"... but anyone who's reconed a speaker should be able to do it without any problem whatsoever, as long as they're very careful...

BTW: the 125A does NOT have a shorting ring at the bottom of the gap, AFAIK...

Regards,
Gordon.

Steve Gonzales
02-02-2005, 11:30 PM
I had a spider come loose on a ESS 12" woofer after I put about 400 watts of power to it. It sounded EXACTLY like a blown speaker! When I removed it to get it reconed, My honest repair guy Marlan Balan (MB sound), spotted the trouble right away while examining it right in front of me. You couldn't tell it was the spider because the surrounds tention made it sit flush as normal, but it only made that sound while being played. Of all the possiblities, I hope this is your problem too-EASY-FIX. Good Luck

pelly3s
02-03-2005, 05:25 AM
ok i'm going with peice of metal or the vc is damaged. i cant even count how many times people bring speakers in that need a refoam and the voice coil and almost crushed because they have been playing it without a foam. its a fun time doing a spider change.