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nfmisso

200037-0 woofer, damaged, repairable?

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I purchased this driver decades ago, and finally got around to looking at it today.  The cone appears to be pushed in, with no travel before hitting bottom.  IT can be pulled out, but almost snaps back to the position in the pictures.  If feels like the voice coil is rubbing.  Before I refoam it, I want to make sure the mechanism is working properly.

Is this repairable?  

Nigel

 

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It appears the the spider has stretched and taken a set in the retracted position.  I've had some success fixing this by spraying down the spider with a rubbing alcohol and water mix, heavier on isopropyl, then fixing the cone in a position where the spider is flat.  You can place spacers like small pieces of wood, popsicle sticks cut to length would work, braced between the underside of the cone and basket.  Then dry the spider with a heat gun or hair dryer.  Since yours appears severe, you may want to position the spider over it's neutral position.  No harm in trying, good luck!

However, you said the coil is dragging - this could be due to the out of position spider and once you replace the surround and align the coil, it will be fine.  Or, if the speaker was played without the surround, the coil could be mushroomed from impacting the bottom of the magnet and in this case, the only solution is a complete re-cone.

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Before doing anything else, you'd be wise to confirm that your woofer still has an active circuit and is not DOA.

1 hour ago, seventy1 said:

It appears the the spider has stretched and taken a set in the retracted position.

This thought might sort of describe what has happened - - I don't know about "stretched", but maybe "sagged" is a more accurate description. Can we assume that this woofer has been stored for decades with the magnetic end in the down position? If so, it is possible that even the minimal weight of the cone assembly has succumbed to the long-term effects of gravity, and without a foam surround holding up the cone's top edge, the spider has fallen a bit and gives the impression that it has weakened when really it might have just have adopted a comfortable position due to such an extended period of neglect.

I just looked at two 037 woofers that I re-foamed not long ago, and they don't appear much different from your pics - - both of them measure 4.9 ohms DCR.  Another pair measured 5.0 and 5.2 ohms. Mine are from AR-18b and AR-18s models - - great little woofers but I dislike that soft dust cap. Without a properly installed foam in place to keep the voice coil centered, it's not at all uncommon to feel some metal rubbing when the cone gets wiggled to and fro. Assuming the driver is not dead, I suspect it is probably repairable.    

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I guess I'm calling it stretched based on observations made on a removed AR 12" cone with spider attached.  Before disassembly, this woofer appeared to have a "sagging spider", which I expected to be more compliant with a loss of stiffness from age.  But what I found was that it still had its stiffness or spring, but it wouldn't stay in the neutral position.  It either wanted to spring up or down, and was stretched into a concave or convex shape.  This is obviously not good for a driver.  Instead of behaving like a spring that wants to hold the cone in a neutral position with a centering force that builds with travel, a stretched spider can act like an over-center spring that has two neutral positions. After the spray/dry process described above, I was able to get it to take a different shape.  I then did the same to an assembled AR 12"and was able to flatten the spider.  No telling if this is a permanent fix, but appears to help.   

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Nigel's woofer has a worn or "collapsed" spider. A careful re-foam using shims will often make a woofer like this serviceable, but power handling will be diminished. This is a case where a less compliant, generic foam replacement can be somewhat beneficial, as it will provide some support for the weaker suspension.

Roy

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I am no expert, but I have refoamed over 50 of these 200001 and 200037 woofers. Your woofer does not look that much different from anything I have seen before. What bothers me is you say there is no up and down movement when you push in on the cone. The cone is naturally going to sagg below the top frame flange because there is no surround to hold it up.  What I do as pictured below is stuff some folded paper towels between the frame and cone to hold the cone as high as possible and keep the voice coil from banging around while cleaning and preparing for the new surround. I also like to put little tick marks around the edge of the cone to make sure new surround is truly centered. Especially helpful because I now only use the filled Boston type surrounds which are a tricker fit than the JBL/Bose type.

hADkZix.jpg 

I glue the surround on next adjusting the towels to keep the cone above the frame flange. After the glue is dry It is time to carefully remove those poly dust caps paying attention not to disturb the  tinsel voice coil leads. Now you can inspect the voice coil and former for any damage. I use a shop vac to clean the gap from any foreign material.

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 Remove the paper towels, Shim the gap and glue and adjust the height of outer surround lip. On these I cut and install flat dust caps (from a organic egg carton) and then fabric mesh dust caps. The fabric looks much nicer than the original poly ones and the flat dust cap makes it fairly air tite. This is how AR did there earlier 8 in woofers. Here they are finished. The ADD series used a foam outer gasket which I have cut here, the S and B series used a plastic trim ring. If you still have the voice coil bottoming out then it is probably a spider problem and a recone is most likely the solution. I have not ran into a bad one yet. One good thing is that these woofers are plentiful and not hard to find. Hope this helps or gives you some ideas, but remember there are many varying techniques and opinions.

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@larrybody  wow!  very detailed, thank you.

Also, thank you to everyone else who responded.

I will probably do nothing with it for a long while.  If someone would like it, I'll give it away, but you have to come and get it in San Jose, CA.

My plan is to build a center channel speaker, with one or two 8" AR woofers (I have a pair of round magnet AR 8" woofers that someone re-foamed and appear to function properly), an AR91 dome mid-range (have one), a MW dome tweeter (need to purchase) and an AR91 crossover network (have one); in a new custom cabinet.  My system is has seven channels: Onkyo TX-RZ810 receiver,  AR9 fronts driven by a Crown XLS 1502 power amp (just right), AR91 rear speakers and AR91.5 side speakers.  Currently I have a NHT center channel.

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That is a very impressive HT setup. If it were me I would just get a pair of AR18 or 18S and wire them in parallel for the center. What kind of subwoofer ar you using? With front 9's and rear 91's and side 915's you probably aren't hurting on the lowend too much.

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2 hours ago, larrybody said:

That is a very impressive HT setup. If it were me I would just get a pair of AR18 or 18S and wire them in parallel for the center. What kind of subwoofer ar you using? With front 9's and rear 91's and side 915's you probably aren't hurting on the lowend too much.

Thank you.  No sub - a sub that matches the low frequency performance of a pair of AR9 speakers are horribly expensive.  The XLS1502 is rated at 525W into 4 Ohms, both channels driven and 775W into 2 Ohms.  It provides plenty of clean power.  More than enough to shake the neighbors house.

I want the center to have the dome mid and dome tweet, like the AR9 family of speakers.

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11 hours ago, nfmisso said:

I want the center to have the dome mid and dome tweet, like the AR9 family of speakers.

That sounds like an impressive system.  Plus, I'd love to see pictures of the custom center, when it's completed.  I'm contemplating a similar center as well.  I have just about everything I need too.  Just lacking the ability to pull it off, I guess?  :blink:

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1 hour ago, Stimpy said:

That sounds like an impressive system.  Plus, I'd love to see pictures of the custom center, when it's completed.  I'm contemplating a similar center as well.  I have just about everything I need too.  Just lacking the ability to pull it off, I guess?  :blink:

thank you.  please don't hold your breath, I have been contemplating this center channel speaker for more than a decade.  I just need to find time, and the confidence to do the job.

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36 minutes ago, nfmisso said:

thank you.  please don't hold your breath, I have been contemplating this center channel speaker for more than a decade.  I just need to find time, and the confidence to do the job.

Me too!  Twin Sons of different mothers...!!!  :)

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On 4/29/2018 at 4:10 PM, larrybody said:

On these I cut and install flat dust caps (from a organic egg carton) and then fabric mesh dust caps.

Larry, that was a fine write-up on how you repair these woofers, and with replacement dust caps, yours look better than mine. I should have done that, too since I dislike the original pliable caps, but I might have stopped at a single flat cap since I've come to appreciate that look on AR-6's and 7's. One question, though: I don't quite understand why you are using the paper towel bunches to lift the cone up when you could do that with the shims in place. Why the extra step? Am I missing something? 

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 RaRa I elevate the cones to scrape and clean the old surround off. It also stabilizes everything. Then I cut the dust cap off and shim. I guess I don't want to get any debii in the gap. The flat dust cap does the trick. I guess the additional mesh dome cap is for show. Just don't like the look of the poly caps.  

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I elevate with plastic bags from the super market.

I also prefer the mesh dust caps since the cap radiates midrange and I believe that 

the mesh is less likely to have a peaked response than hard plastic.

Where do you get the mesh caps?

Weber sells some here, I think the DCB is a mesh cloth, but not positive:

https://www.tedweber.com/other-stuff/recone-parts?p=3

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21 hours ago, Pete B said:

Where do you get the mesh caps?

Thanks for the source, That place is 20 minutes north of my town. I have used the auction site to get some from a place in Las Vegas. Also discovered this place.

www.midwestspeakerrepair.com/shop/speaker-repair-kits/screen-dust-caps/

Have not ordered anything yet, but the price seems very fair.

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