ADVENT 5012 WOOFER QUESTION

[DON]

I have a pair of 5012s that appear to be in good shape except for a mashed in corner and the woofers. When I bought them I knew that the woofers had to be refoamed but after examining them I think they may need more than that. I can't find the so called "sweet spot" when I press the cone down. There is a scraping sound that wont go away and the cone has quite a bit of side to side movement. I connected an AA battery and the cone moves in and out with the spider. I can't see any looseness between the spider and the cone. I suspect that they have been played without the surrounds. From what I've said does it sound as if they will need to be reconed? I haven't tried playing them but I have a CD with a 30hz tone and members on another forum suggested I might try playing this CD at a low volume.

Woofers for these are rare and costly and reconing costs about $45-$50 each. I don't mind the cost of reconing but I'm concerned about the quality of the reconing kits/service available. Any advice would be helpful.

[JKent]

Hi Don

I would send them to Bill LeGall of Millersound in PA. If you go on their website and describe the symptoms he may be able to diagnose the problem and give you a repair estimate. He's a real wizard when it comes to speaker repair.

Kent

[DON]

Hi Don

I would send them to Bill LeGall of Millersound in PA. If you go on their website and describe the symptoms he may be able to diagnose the problem and give you a repair estimate. He's a real wizard when it comes to speaker repair.

Kent

Thanks Kent. I'll give him a call tomorrow.

[Pete B]

Thanks Kent. I'll give him a call tomorrow.

It is very difficult to find the sweet spot without having

intact foam - I'd say that what you are seeing is normal.

You should make sure that your meter is properly zeroed,

measure and tell us the DC resistance.

I would try refoaming them before sending them out for

more work.

[DON]

It is very difficult to find the sweet spot without having

intact foam - I'd say that what you are seeing is normal.

You should make sure that your meter is properly zeroed,

measure and tell us the DC resistance.

I would try refoaming them before sending them out for

more work.

Pete at the risk of lsounding like an electronic virgin how do I measure DC resistance? I measured about 7 OHMS resistance. Thanks for replying.

[Pete B]

Pete at the risk of lsounding like an electronic virgin how do I measure DC resistance? I measured about 7 OHMS resistance. Thanks for replying.

You measure it with a DVM or whatever ohm meter you might have.

Sorry, I was just being specific about it being DC but that is

what a meter does. 7 ohms is high, short the leads of your

meter and see if it reads 0 ohms, if not there should be an

adjustment to "zero" it. It should be about 4 to 5 ohms, maybe

6 at max if I remember correctly.

Are you comfortable using your meter? You might want to read

up on using one if not.

Let me also ask, do the woofers have round or square

magnets? The round magnet version was made by Jensen and had

a tighter gap, it seems than the older woofers. So, they are

just a bit more fussy about centering.

[DON]

I'll recheck my meter for zero and measure the woofer again. The magnets are the square type. I have another set ready for refoaming and they are easy to center.......they also have the square magnet. I seldom use my meter except for resistance and battery checking. It's a digital meter from Sears costing $40 and probably good enough for what I need but the users manual could be more detailed. I tried measuring DC voltage at the speaker terminals on two used amps I have and got a reading of .016 and I'm not sure what mv that is.

Thanks Pete

Edit: I was wrong about the magnets on the other woofers......they are round. I rechecked the resistance on the woofer and got 5 OHMS.

[Doug G.]

Don,

.016 is 16mV which is fine.

I agree with Pete that finding the spot with no rubbing is difficult without surrounds in place. I have bought several Advent woofers that seemed really bad before refoaming but are perfect after.

Refoaming is a good idea.

Doug

[DON]

Don,

.016 is 16mV which is fine.

I agree with Pete that finding the spot with no rubbing is difficult without surrounds in place. I have bought several Advent woofers that seemed really bad before refoaming but are perfect after.

Refoaming is a good idea.

Doug

Thanks Doug. That's what I thought the reading was. I refoamed one woofer last night but I haven't glued the surround to the metal frame yet. I'll do that today and see if it will center while receiving a 30hz signal. I thought the Advent 5012 was the same as the 25th Aniverssary models but I found the cabinet sized are slightly different. The 5012s I have are about 1/2" taller(set).

[Pete B]

Edit: I was wrong about the magnets on the other woofers......they are round. I rechecked the resistance on the woofer and got 5 OHMS.

Is this the one that you previously measured at 7?

That is good if it is actually 5.

Because if it is really 7 then there is probably an

issue with the voice coil.

[DON]

Edit: I was wrong about the magnets on the other woofers......they are round. I rechecked the resistance on the woofer and got 5 OHMS.

Is this the one that you previously measured at 7?

That is good if it is actually 5.

Because if it is really 7 then there is probably an

issue with the voice coil.

This is the one I thought measured 7. I haven't removed the other one yet.

[Pete B]

This is the one I thought measured 7. I haven't removed the other one yet.

That's good, so I would go ahead and refoam them.

[DON]

That's good, so I would go ahead and refoam them.

I tried centering the cones last night using 30hz tone after attaching the foam. The cone won't center itself and there is a constant knocking when playing the test tone. I can eliminate the knocking by pushing the cone to one side. Is it normal to have to push the cone in line or should it line up automatically?

[Doug G.]

In my opinion, the 30Hz deal isn't all it's cracked up to be as I don't see how it can actually "center" the voice coil. There is too much mass involved with the cone and everything.

As it is, the cone is already centered at the cone/voice coil former junction by the spider if the spider is in good shape. So, the only thing the refoamer has to do is ensure that the voice coil is parallel all along its length to the pole piece.

I have always just done it by feel while the glue is setting up. It's really not difficult and you get a "feel" for it after you do a few.

When the VC is correctly centered and parallel, you can push down anywhere on the face of the cone and there should be no rubbing. This includes way out near the surround at a single spot.

If it seems impossible to get the cone into a position where the VC doesn't rub, it indicates that there is, indeed, some damage to the VC and the cone will have to be removed and examined.

Doug

[DON]

Hi Don

I would send them to Bill LeGall of Millersound in PA. If you go on their website and describe the symptoms he may be able to diagnose the problem and give you a repair estimate. He's a real wizard when it comes to speaker repair.

Kent

Thanks Kent. I need to e-mail Bill.

[Pete B]

I tried centering the cones last night using 30hz tone after attaching the foam. The cone won't center itself and there is a constant knocking when playing the test tone. I can eliminate the knocking by pushing the cone to one side. Is it normal to have to push the cone in line or should it line up automatically?

Are you saying that you glued the foam to the cone, and are testing to see if it will center without glue to the basket?

Or is the glue to the basket wet and you can't get it to center?

If you want or feel that you need to practice/experiment some people glue to the cone, then use binder clips around the basket to do a test fit.

I usually find that centering by eye will get you very close, then use a "push test" to see if you need to adjust a bit here or there. You can

also run them a bit at 20 Hz or so to see if you get any scraping sounds, but I would push down again on the glued joing if you do it before it is dry.

I run most of mine, the early Advents, right up to full excursion at resonance. The early drivers handle this easily since they are so rugged, I would not try it with a Jensen where the voice coil hits the back plate since they are not as robust.

I believe that the Jensen voice coil former is thinner and probably aluminum that allowed for a more efficient motor and as a guess more linear Xmax as a trade for the higher field strength. I don't have a blown Jensen driver to take apart and check this theory.

[DON]

Are you saying that you glued the foam to the cone, and are testing to see if it will center without glue to the basket?

Or is the glue to the basket wet and you can't get it to center?

If you want or feel that you need to practice/experiment some people glue to the cone, then use binder clips around the basket to do a test fit.

I usually find that centering by eye will get you very close, then use a "push test" to see if you need to adjust a bit here or there. You can

also run them a bit at 20 Hz or so to see if you get any scraping sounds, but I would push down again on the glued joing if you do it before it is dry.

I run most of mine, the early Advents, right up to full excursion at resonance. The early drivers handle this easily since they are so rugged, I would not try it with a Jensen where the voice coil hits the back plate since they are not as robust.

I believe that the Jensen voice coil former is thinner and probably aluminum that allowed for a more efficient motor and as a guess more linear Xmax as a trade for the higher field strength. I don't have a blown Jensen driver to take apart and check this theory.

I've been on a short break from working on the Advent's surround. I've been busy removing dents and scratches from 4 Advent boxes and then going over them with Roberts. They're looking very good except for some deep scratches I decided to leave alone. The wet cloth and iron work very well removing dents/scratches but it also raises the grain and that requires a light sanding and I try to avoid sanding as much as possible.

Back to the woofers. I have the surround glued to the cone and it's ready for gluing to the frame. The "knocking" I heard was the surround slapping against the frame. I can easily find the center when the 30hz signal is applied so I'll just have to hold it a bit while the glue dries on the frame. Thanks for the help!

[dynaco_dan]

I've been on a short break from working on the Advent's surround. I've been busy removing dents and scratches from 4 Advent boxes and then going over them with Roberts. They're looking very good except for some deep scratches I decided to leave alone. The wet cloth and iron work very well removing dents/scratches but it also raises the grain and that requires a light sanding and I try to avoid sanding as much as possible.

Back to the woofers. I have the surround glued to the cone and it's ready for gluing to the frame. The "knocking" I heard was the surround slapping against the frame. I can easily find the center when the 30hz signal is applied so I'll just have to hold it a bit while the glue dries on the frame. Thanks for the help!

Hi there

I used a tone from a cd sold by Stereophile many years ago.

When the white glue had set with the surround to foam connection, I ran a very low level, perhaps 100 hertz, to cause the

back and forward movement of the woofer.

Gently touching the outer most portion of opposing sides of the surrounds, I would then, ever so gently, slide the cone from one side

to the other.

At some point there would be the rubbing noise.

I would then do the opposite direction and again it would buzz.

At each buzz I noted where that surround edge was and eventually there was a pattern.

I then applied a small drop of glue on opposite sides and tried the woofer again.

I would then very gently push the cone in one direction, then the other, to see whether there was equal clearances.

After confirming a very closely centered voice coil, I ran a bead of glue under the balance of the surround.

This is a slow, but for me, a successful way of refoaming a woofer.

Obviously this will only work with a large magnetic gap, not JBL, Altec, or EV, etc.

[Doug G.]

Sounds like a pretty good technique, Vern

Doug

[dynaco_dan]

Sounds like a pretty good technique, Vern

Doug

Hi Doug

Thank you.

The only thing I forgot to mention was that if the spider was sagging, my approach would not have worked.

My first woofer took me about 1 1/2 hours to complete, the second about 10 minutes.

[DON]

Hi there

I used a tone from a cd sold by Stereophile many years ago.

When the white glue had set with the surround to foam connection, I ran a very low level, perhaps 100 hertz, to cause the

back and forward movement of the woofer.

Gently touching the outer most portion of opposing sides of the surrounds, I would then, ever so gently, slide the cone from one side

to the other.

At some point there would be the rubbing noise.

I would then do the opposite direction and again it would buzz.

At each buzz I noted where that surround edge was and eventually there was a pattern.

I then applied a small drop of glue on opposite sides and tried the woofer again.

I would then very gently push the cone in one direction, then the other, to see whether there was equal clearances.

After confirming a very closely centered voice coil, I ran a bead of glue under the balance of the surround.

This is a slow, but for me, a successful way of refoaming a woofer.

Obviously this will only work with a large magnetic gap, not JBL, Altec, or EV, etc.

Thanks Vern. I've been working on my woofer using a method very similar to yours but I haven't applied the glue yet.

[Doug G.]

I want to clarify my earlier post about using a 30Hz (or other frequency) tone to center the VC.

I only meant that I don't believe the tone itself will center the cone as I have understood some enthusiasts (not here) claim.

It can, however be useful to move the cone up and down to check for rubbing as the glue starts to set and getting the VC centered as Vern did.

It's just that I'm too impatient and lazy to hook a CD player and amp up to the speaker to do that. That's why I just center the VC by feel, manually moving the cone up and down.

Doug

[DON]

I want to clarify my earlier post about using a 30Hz (or other frequency) tone to center the VC.

I only meant that I don't believe the tone itself will center the cone as I have understood some enthusiasts (not here) claim.

It can, however be useful to move the cone up and down to check for rubbing as the glue starts to set and getting the VC centered as Vern did.

It's just that I'm too impatient and lazy to hook a CD player and amp up to the speaker to do that. That's why I just center the VC by feel, manually moving the cone up and down.

Doug

Once I had the surround glued to the cone it was possible to center the cone by hand. I used the 30hz tone to help center the cone when I glued the surround to the frame. I haven't put it back in the cabinet yet since I may try rebuilding the crossover. One X over fell off the back of the cabinet and should be easy to rebuild. I'm hoping I can get the other X over loose as well. Thanks for your help.