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Altec Voice Coil Rub.... What to do?

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dumptruck

Lunatic Member
I bought a pair of 414Z in bartertown recently. They were fine for three weeks after arrival, and then last night I found both were suddenly rubbing pretty good (one has just been sitting around, one has been mounted and receiving test signals for measurement). I didn't mess with them last night, and just now when I went to check them out, I find the one sitting out is back to normal! The mounted one is still rubbing. A little pressure toward the ground, as it is currently oriented, allows it to move in and out cleanly.

What is a guy to do? I can't imagine these being very useable if they are going to shift in and out of alignment all the time. All I can come up with is to try reflowing the surround goop and see if that helps?

The surround goop doesn't have any big clumps/runs, but you can see that it is a little thicker on one side, along the inner edge of the surround.

I'm not sure if it's at all possible to judge the alignment of the pole and magnet without dissecting the whole driver? The three sections of the motor assembly are not perfectly aligned from the outside (~1/2mm off), but the welds look intact...

:dunno: Starting to wish I'd chosen brand new woofers here. :sigh:
 
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A couple thoughts.

Are your baffles a perfect plane, and/or is their anything stuck to the back of the mounting rims that could pull the basket out of alignment when tightened down?

Are you getting buzzing or other audible anomalies? or is the rubbing occurring only when the cones are moved manually?

Tight gaps in those woofers, they can be a bit finicky.
 
These can only be rear mounted due to how the frame is shaped. The one currently mounted is just using the paper gasket, and I tried to mount it as gently as possible. It will come out tonight, though.

The last time I put anything through them, they did not have this rub, so I don't know for sure if it would happen with a real signal, but I am pretty sure it would. I daresay my cone-pushing finesse is top-notch. :D Seriously, though, the combination of the tight gap and fairly flexible suspension+cone make it pretty easy to feel what's happening by hand as long as you've got a light touch.
 
Did you try to invert the driver 180 degrees when mounted. You may just be experiencing a bit of sag. Kind of like my face. :yes:
 
Well, it seems to be sagging against gravity at the moment (and the other one was sitting face-up when it developed, and then lost, a rub). I was/am thinking about taking a hair dryer to the surround with it mounted the way it is now...
 
Hi,
I had a mysterious "slight rub" on a woofer I recently refoamed. As it turned out the glue holding spyder to basket was dried-out and crumbly. I did not catch the first time through because the spyder appeared to be laid down flat. I started poking around a bit with a exacto knife and wha-la, the glue was gone on about 2/3 aroung the periphery of the spyder, the other driver was doing the same just not as advanced.

just a thought
 
Late night bump for any other advice. I have to do some work work, so messing with these will not be tonight after all.
 
Not Altec but I've eliminated voice coil misalignment by rotating, torquing on different frame bolts, and treating the spider. I know that a lot of experienced Altec users rotate their woofers as a maintenance item and some go as far as redoping surrounds that have remained mounted in the same position and the doping has run towards the bottom.
 
Hey Dumptruck. Dave here (the guy who sold the 414z's to you). I was disappointed to see your thread last night concerning the vc rub. I have the other two 414z's here that I'm still planning a project with.

After hearing what's going on, I went to the basement to check my woofers. One of them was now rubbing just like yours (they have been laying face down on a bench for a couple weeks. Not just a little rub, but pretty obvious.

This morning I was gently moving the cone back and forth trying to discern which way it needed to shift to eliminate the rub. Then I got out the hair dryer. I held the woofer vertical so gravity was pulling in the proper direction.

Heating the surround, I could not detect any movement of the goo and really didn't think this was going to do the trick. But lo and behold I turned off the dryer, laid down the woofer and depressed the cone. To my surprise, no rub at all. I can't believe these are that finicky.

My thoughts are that the cone is not so much moved laterally, but rather tilted or sagging in one side. Like I said, there was no noticeable migration of the dope when I heated it, but I think heated the surround possibly just softens it enough to allow it to return to it's centered position. I'm thinking that the surround really has a memory and wants to be centered if given the opportunity.

My fear is that after resting, it may go back. I hope not. It's only been 15 minutes since I warmed it. It has cooled completely and still absolutely no rub. I hope this helps, and if you want more info on what I did, pm me. I'm really sorry that yours has the rub too, but I hope this gives you a glimmer of hope.
 
I can't believe these are that finicky.
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Tight gap, minimal clearance.

My thoughts are that the cone is not so much moved laterally, but rather tilted or sagging in one side.
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They warp, sometimes just the way they unevenly absorb moisture out of the air can temporarily change their shape. The heat from the blow dryer probably changed the shape of the cone just enough to correct the misalignment.

When installed in a cabinet, the cones are only subject to half as much short term humidity impact which lends to stability.

FWIW, i don't manually try to move Altec cones anymore. A sinewave between 20-30hz at a few hundred miliwatts will reveal any rubbing/alignment issues without damaging anything.
 
bowtie427ss said:
Tight gap, minimal clearance.

They warp, sometimes just the way they unevenly absorb moisture out of the air can temporarily change their shape. The heat from the blow dryer probably changed the shape of the cone just enough to correct the misalignment.

When installed in a cabinet, the cones are only subject to half as much short term humidity impact which lends to stability.

FWIW, i don't manually try to move Altec cones anymore. A sinewave between 20-30hz at a few hundred miliwatts will reveal any rubbing/alignment issues without damaging anything.
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Thanks, good to know. A surround that sags un-evenly seems almost the same as a warped cone, or at least tough to distinguish between which one of those is happening. I'm not convinced that cone warp is more likely than surround and goop sag/warp, but you may be right.

Mine as of this moment is still completely rub-free.
 
Hey Dave, don't worry I wasn't thinking of complaining to you. I'm know these were fine until just the other day, and as I looked around online I started to realize just how normal this is with old Altecs. Sounds like you did exactly what I was thinking about. There isn't a hairdryer in this house though, I'll have to borrow one. I'm quite confident I can coax them both into good alignment, I'm just worried about them staying that way, as you are. Your description of the cone tilting slightly matches my impression, but it's very hard to tell without being able to see into the gap, of course.
 
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dumptruck said:
Hey Dave, don't worry I wasn't thinking of complaining to you. I'm know these were fine until just the other day, and as I looked around online I started to realize just how normal this is with old Altecs. Sounds like you did exactly what I was thinking about. There isn't a hairdryer in this house though, I'll have to borrow one. I'm quite confident I can coax them both into good alignment, I'm just worried about them staying that way, as you are. Your description of the cone tilting slightly matches my impression, but it's very hard to tell without being able to see into the gap, of course.
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Yeah, the reason I feel that it's tilting is based on the way I had to move the cone to get it to not rub. Then after coming to that conclusion I think I could actually see how the surround was sagged a little on one side vs the other.

My laymans theory is that these set for years, used or unused and gravity applied forces to the cone, spider, surround, not to mention the black goo that you can see has migrated to one side a little (which is very mild to a lot of these that I have seen migrate far enough to glue the gasket to the cabinets).

I think after all that, they remained centered maybe because they were in use and broke-in that way (it seems like being energized has it's own tendency of keeping things centered). If that may be true, than what you have is a surround/cone situation where there is uneven tension around the perimeter that is corrected by the gravity because that is the way they broke-in.

Then they lay flat or upside down or whatever for awhile and all the forces change and that uneven tension starts pulling.

I think heating the surround my soften up the goo and the fabric enough to allow that tension to equalize again.

And than there is the warped cone theory which is slightly different, but also plausible. All I know is, as of right now the heat worked.
 
rrrrrrrr now it seems to be changing just sitting on a chair for 30 min. If these were just a little bit lesser drivers I would already be cutting the surround off the cone, removing the dust cap, and showing it what's what.
 
dumptruck said:
Okay, I'm not getting anything from the hair dryer. Can you describe how you went about it a little more?
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Hey Dumptruck. I put my speaker that was rubbing back where it was in my basement to see if the problem re-occurs. I checked it this morning and the cone moves completely silently.

Here's what I did. I determined which way the cone needed to tilt in order to go center. That determines that there is a low side and a high side to the surround. My high side more or less was on the side of the surround where the goop had migrated.

I sat down and propped the speaker upright on my thigh. And oriented the goopiest part first at the 9 o'clock position and heated from there down. Then I rotated that point 180 degrees to 3 o'clock and heated from that point down. I thought this way if the goop softened, gravity could pull it through the valleys in the accordion surround. I attached a sketch to try to show what I mean.

I had the hair dryer heat on high and the blower on med. I also cupped my hand over the intake to restrict airflow in an attempt to up the temperature. I was thinking it was not hot enough and was about to break out the heat-gun when I realized it was not rubbing anymore.

This is pretty un-scientific, and it's hard to tell just what went on to make it center. I'm starting to thing the build up of goop in the accordion valleys on the one side of the cone may be the biggest factor contributing to un-even behavior in the surround.

Did you soften the surround 180 degrees on the thick side of yours? I'd focus the heating efforts on the accordion part. If I can describe this better by phone, PM me and I will give you my number.
 

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Just thought I'd update here. Checked the woofer this morning(been in the basement for several days). It's rubbing again. I'm going to run the dehumidifier for a day or so just to see if there are any changes.
 
Well, I'm not really have much luck. I messed around with the hair dryer - did some stuff like bobbyonions describes, tried using a battery to hold the cone and stretch the surround while doing it, tried warming the surround and then working it with my fingers a little... I did get some improvement, but nothing that seems like it's going to stick.

So... maybe I'll set them aside to sent to great plains someday and go back to my Beyma woofer plan for this project, or maybe I'll throw caution to the wind and get that dust cap off.. not sure yet.
 
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