DQ-1W bad juju

Copa1934

My ears are bleeding
Subscriber
DQ-1W bad juju, gone good juju...

I'm finally taking on rebuilding my buddies sub and can't believe what I've come up against.

First the sub was purchased used from a mutual friend. The sub quit working, as we were told, so it was picked up cheap. This friend is NOT known to abuse equipment, but in fact has a high regard for stuff audio and uses tube equipment almost exclusively.

Problem? Cone locked up but solid. Very solid, and it gets worse.

Fast forward. I de-soldered the leads, cut the spider. Still no play. Found out, purely by accident/experimentation, that the rubber surround could be pulled away from the frame almost with ease. Blew me away how easy. Just needed to start from the very edge, inside the frame, using a paint can opener (working it slowly between the surround and lip of the frame).

So, surround removed from frame, spider cut, no luck. OK, pulled the dust cap to get a looky inside. Hmmm, something not right here. I was actually able to work the cone off the VC and remove the cone and surround intact. OH it gets better still. VC left in gap.

I grab the VC and try working it loose. No go. Hmmm. Closer examination and WTF? The gap actually was different. Tighter on one side than the other. No way, the pole is shifted? I check the magnet structure, not loose and no obvious signs it's been moved. Place a ball peen against one of the metal plates and hit with another hammer. Solid, positively solid! Dang!

My thoughts? I'm wondering if this one got through, somehow, with the pole off but not enough to cause rubbing. After sufficient playing, the VC heated up, rubbed causing friction and more heat and then expanded AND bonded between the pole and plate?

The speaker and the driver show no signs of having been dropped or jarred so it's a wonder how this happened, other than leaving the factory this way.

Is it possible to salvage this? It's one thing to re-attach a magnet structure, but to intentionally remove one and and then re-attach?
 
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Sorry to hear about your troubles, this is the SEAS 33F-WKA-DQ 13 inch woofer?

Do you have pics of what you found?
 
Enjoy...

Sorry to hear about your troubles, this is the SEAS 33F-WKA-DQ 13 inch woofer?

Do you have pics of what you found?

The screw driver was rested in the gap to show how large it was. The opposite side it completely sandwiched. Never seen anything like it before.
 

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That's a blown woofer with a rotten surround. Recone it, complete with new voicecoil or replace it. That's what happens to woofers when you play them too loud. And all foam surrounds rot with time. They're probably close to forty years old.
 
Loosen the screws to re-align the voice coil gap. Also avoid hitting magnets with hammers-shock can crack ferrite magnets, and also possibly demagnetize or partially demagnetize them. It needs a re-cone. You might check with Regnar for a recone kit.
 
That's a blown woofer with a rotten surround. Recone it, complete with new voicecoil or replace it. That's what happens to woofers when you play them too loud. And all foam surrounds rot with time. They're probably close to forty years old.

The surround on these SEAS woofers are a fairly thick rubber surround. IME, I've seen very few of them even crack, but of course they can dry out and crack.

I'm not sure though how the pole piece shifted unless it was glued onto the back plate. The only way to check is to see if the center pole piece, which is not an alnico magnet slug, shifts around when there is force applied to it by the screwdriver or some implement. That would prove its loose.

Loosen the screws to re-align the voice coil gap. Also avoid hitting magnets with hammers-shock can crack ferrite magnets, and also possibly demagnetize or partially demagnetize them. It needs a re-cone. You might check with Regnar for a recone kit.

Its my understanding that ferrite is pretty impervious to demagnetizing. I thought it was alnico that can't take shock or high temps.
 
The surround on these SEAS woofers are a fairly thick rubber surround. IME, I've seen very few of them even crack, but of course they can dry out and crack.

I'm not sure though how the pole piece shifted unless it was glued onto the back plate. The only way to check is to see if the center pole piece, which is not an alnico magnet slug, shifts around when there is force applied to it by the screwdriver or some implement. That would prove its loose.



Its my understanding that ferrite is pretty impervious to demagnetizing. I thought it was alnico that can't take shock or high temps.
You are correct on all accounts. I've rebuilt quite a few drivers so I'm not new to this.

The cone and surround are totally intact and can be reused, needing only the VC and spider, both of which I already have. The replacement cone I'll send back, doesn't look like a correct fit. Different design and the cone isn't as stiff as the original.

I tried prying with no luck at all. I think a couple people missed the point the pole had shifted. Literally had the VC pinched against the plate.

I definitely didn't tap the magnet. I did that once many years ago and cracked a magnet. Never did that again. The plates absolutely will not budge, so I'm figuring they may have been glued that way. Factory defect?

This is NOT a typical 12". Bigger than all my 12" spares (including some JBL drivers), by more than an inch. So I'm not anticipating this going smooth or easy.

Oh, the surround is very pliable, in great shape and separated from the frame nicely.

Thanks for the input.
 
I bought a used scanspeak tweeter from a very reputable seller on another forum. I packed them away after reciving them in an undamaged box for about two years. Two years later I find out one pole was broken and the tweeter was trash. There was no evidence on the box of abuse either. Assuming the seller was honest, I really think that it was just a defectively assembled tweeter. Could have been the same scenario with that woofer.
 
Wow, that's a shame. Other than the VC being totally whacked, it appears to be in fantastic shape.

Look forward to the reconstruction. :lurk:
 
You are correct on all accounts. I've rebuilt quite a few drivers so I'm not new to this.

The cone and surround are totally intact and can be reused, needing only the VC and spider, both of which I already have. The replacement cone I'll send back, doesn't look like a correct fit. Different design and the cone isn't as stiff as the original.

I tried prying with no luck at all. I think a couple people missed the point the pole had shifted. Literally had the VC pinched against the plate.

I definitely didn't tap the magnet. I did that once many years ago and cracked a magnet. Never did that again. The plates absolutely will not budge, so I'm figuring they may have been glued that way. Factory defect?

This is NOT a typical 12". Bigger than all my 12" spares (including some JBL drivers), by more than an inch. So I'm not anticipating this going smooth or easy.

Oh, the surround is very pliable, in great shape and separated from the frame nicely.

Thanks for the input.

This woofer is specified by SEAS as a 13 inch woofer, not quite sure why the deviation from standard but it is 33cm diameter, a nice round metric number. Sort of like JBL's line of 14 inch woofers, a tweeter.

Here's the spec sheet from SEAS (and archived by others too) with the original specs using an concave sealed center cap - Dahlquist specified a convex open linen dust cap, probably for better breathing, cooling and maybe just a bit of relaxation from purely sealed.

http://www.seas.no/images/stories/vintage/pdfdataheet/h097_and_h190_33f-wka_and_dd.pdf

This same woofer is used in the rare and larger Rogers L35B Reference System subwoofer built to use with their LS3/5a and in a number of SEAS Kits of the early 80's. Modified versions with more damping coating applied are used by B&O in their TOTL BEOVOX M100 monitors.

rogers_23__50450.1368027446.1280.1280.jpg
rogersls35bsubwoofer2.jpg


110564-bang__olufsen_beovox_m100_speakers_for_leaf_tickets.jpg
110567-bang__olufsen_beovox_m100_speakers_for_leaf_tickets.jpg
 
This woofer is specified by SEAS as a 13 inch woofer, not quite sure why the deviation from standard but it is 33cm diameter, a nice round metric number. Sort of like JBL's line of 14 inch woofers, a tweeter.

Here's the spec sheet from SEAS (and archived by others too) with the original specs using an concave sealed center cap - Dahlquist specified a convex open linen dust cap, probably for better breathing, cooling and maybe just a bit of relaxation from purely sealed.

http://www.seas.no/images/stories/vintage/pdfdataheet/h097_and_h190_33f-wka_and_dd.pdf

This same woofer is used in the rare and larger Rogers L35B Reference System subwoofer built to use with their LS3/5a and in a number of SEAS Kits of the early 80's. Modified versions with more damping coating applied are used by B&O in their TOTL BEOVOX M100 monitors.

rogers_23__50450.1368027446.1280.1280.jpg
rogersls35bsubwoofer2.jpg


110564-bang__olufsen_beovox_m100_speakers_for_leaf_tickets.jpg
110567-bang__olufsen_beovox_m100_speakers_for_leaf_tickets.jpg
I'm sorry, I thought it was a 12" woofer. Now it makes sense, the size that is. Geez, like the Mach One/Two/Three woofers, which are billed as 15" but really more like 14".

Nice subs and speakers!

Waiting to hear back from my friend. He's gonna have to figure out what to do next.

So I'm guessing not readily available? Any suggestions on a suitable replacement?

Thanks for the replies.
 
That is very similar to what happend to the 035ti tweeters in some JBL L20T I purchased. I bought 4, 2 I found the magnet with pole piece had fallen off the front plate and taking the voice coil with it. Then my daughter knocked one of my 2 good ones off the stand onto the carpet. Cabinet was fine, but the tweeter was muffled. When I opened it up I saw the magnet had shifted on the front plate, the glue had given out like the others, and it was pinching the voice coil, exactly like your picture.

I was able to repair one of the voice coils, and when I tried to set the magnet back on the front plate it attracted and snapped very strongly, and not aligned. I had to insert a screwdriver in the gap, shims, and pry the pole piece around against the shim so the gap was even. This was NOT easy, and this is for a tweeter. I am still trying to get 1 functioning tweeter so i have a pair again.

I believe when drivers are assembled the magnet structure is aligned and glued, then the magnet is magnetized. If only glue is holding it, and that glue fails, a jolt will cause the magnet and pole to shift with respect to the mounting surface, just like your picture. This was also a problem on some JBL woofers I learned while researching my problem

Once it has shifted, it is VERY difficult to align it again. I had trouble with a tweeter magnet, not sure it will be possible at all with a magnet as strong as you have there.

Sorry for your dificulties, good luck to you
 
I'm sorry, I thought it was a 12" woofer. Now it makes sense, the size that is. Geez, like the Mach One/Two/Three woofers, which are billed as 15" but really more like 14".

Nice subs and speakers!

Waiting to hear back from my friend. He's gonna have to figure out what to do next.

So I'm guessing not readily available? Any suggestions on a suitable replacement?

Thanks for the replies.

They are available, just not easy to find or to source quickly. Do you only have one that is bad, right?

Might be worth putting a wanted in BT, you never know what might pop up.
 
They are available, just not easy to find or to source quickly. Do you only have one that is bad, right?

Might be worth putting a wanted in BT, you never know what might pop up.
I'll have my buddy do the shopping.

Thanks
 
Update...

So had a lull in my regular work related duties and decided to take another crack at this bugger. I had already removed the screws and tried to move, to no avail thank goodness. I decided to try something different, with no rhyme or reason behind it.

I took two small pry bars, which I have many, and a block of wood and with the driver face down placed the pry bars under the magnet and lifted and the bugger came right off, with ease I might add. Having that much leverage helps BUT it should not have come off that easy. Should have been more effort and soon I would discover why.

Seems the adhesive had become just brittle enough for the magnet to shift, possibly being bumped or something. I've taken so more images and will post later.

I now have the pieces cleaned up and will work on a shimming/alignment device. Not going to be easy since I need to use something non-ferrous, which I'm sure people here understand why. Maybe later this week I'll be able to begin assembly.

I've kinda been on a role with speaker rebuilds of late.
 
Wooohoooo, progress...

Nearing the finish line. Can't wait to post images.

Have new VC, spider and original cone (which I thankfully was able to salvage) installed. Running new leads. Will attach surround to frame and install dust cap tomorrow. Hopefully testing later tomorrow or Wed.

This has worked out better than anticipated and easily as well as I had hoped. Hopefully others will learn from my example with the cheap alignment tool. Worked out beautifully. Doesn't appear videos can be attached so I'll have to post that on YouTube and link here.
 
Following this entry for continuity...

So had a lull in my regular work related duties and decided to take another crack at this bugger. I had already removed the screws and tried to move, to no avail thank goodness. I decided to try something different, with no rhyme or reason behind it.

I took two small pry bars, which I have many, and a block of wood and with the driver face down placed the pry bars under the magnet and lifted and the bugger came right off, with ease I might add. Having that much leverage helps BUT it should not have come off that easy. Should have been more effort and soon I would discover why.

Seems the adhesive had become just brittle enough for the magnet to shift, possibly being bumped or something. I've taken so more images and will post later.

I now have the pieces cleaned up and will work on a shimming/alignment device. Not going to be easy since I need to use something non-ferrous, which I'm sure people here understand why. Maybe later this week I'll be able to begin assembly.

I've kinda been on a role with speaker rebuilds of late.

Here are images of the separated pieces. Nice and clean, i.e. no damage from prying apart. Visually it was obvious the adhesive had lost adhesion, however, I can't say if from heat or what. I see no indications of heat (discoloring of the steel).
 

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So what to do next?

I've seen a number of posts on magnet assembly and most seemed over complicated. I came up with a solution for my AR3a tweeter, but the DQ woofer is a lot larger. So what to do? I have access to plastic tubes, and realized that the gap was tight enough that all I need do is match the I.D. of the plate. So test fitting a variety of tubes I found one that not only fit the plate snug, it was undersized, meaning it would need enlarging to fit the pole piece.

Using my drill press I tried a abrasive wheel (shown) then a drum sander but it was going way too slow. Next I tried another attachment, a type of sanding drum for drills. Brilliant tool. This worked much better and left a smoother finish on the inside.
 

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