SDA 1C driver repair question
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WilsonCA
Posts: 10
Hi folks. This is my first post here. Forgive my ignorance. Thanks for any help you can offer!
I've been lurking a bit on the threads trying to troubleshoot a set of SDA 1C speakers I got on Craigslist. I have read up on re-centering the magnets and epoxying my working drivers. I have two MW6511s on the Left speaker that have an audible bit of buzzing or distortion when I play music. I assessed all the drivers by pushing the cone back, and these two are rubbing, one more than the other. All my other drivers seem good.
So I pulled out the two problem 6511s and was getting ready to make a jig and attempt to repair them. But the magnets seem to be strongly adhered. I cannot separate the unit anywhere, whether between the front plate and the basket or the magnet, or between the back plate and the magnet. Everything is solid, no budge at all. My impression from reading so far is that it should not be this hard to separate the plates if the adhesive has failed.
So my question is whether there might be something else going on, and how to check for other issues. There is definitely a friction on the voice coil. It occurs to me that someone may have already attempted to recenter these, and did not succeed. If that's the case, I would appreciate advice on how to separate the plates so that I can try again.
I've been lurking a bit on the threads trying to troubleshoot a set of SDA 1C speakers I got on Craigslist. I have read up on re-centering the magnets and epoxying my working drivers. I have two MW6511s on the Left speaker that have an audible bit of buzzing or distortion when I play music. I assessed all the drivers by pushing the cone back, and these two are rubbing, one more than the other. All my other drivers seem good.
So I pulled out the two problem 6511s and was getting ready to make a jig and attempt to repair them. But the magnets seem to be strongly adhered. I cannot separate the unit anywhere, whether between the front plate and the basket or the magnet, or between the back plate and the magnet. Everything is solid, no budge at all. My impression from reading so far is that it should not be this hard to separate the plates if the adhesive has failed.
So my question is whether there might be something else going on, and how to check for other issues. There is definitely a friction on the voice coil. It occurs to me that someone may have already attempted to recenter these, and did not succeed. If that's the case, I would appreciate advice on how to separate the plates so that I can try again.
Answers
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Check that the spider has not detached from the cone.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Hey, thanks for that suggestion. Will take a closer look later today (I'm writing this in line at the DMV, LOL).
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More than likely, there is galvanic corrosion on the base plate ID rubbing the coil and/or saggy suspension/spider.Don't take experimental gene therapies from known eugenicists.
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Hey, thanks for that suggestion. Will take a closer look later today (I'm writing this in line at the DMV, LOL).
The spider/cone doesn't have to be completely detached to cause an issue like you are describing, so inspect thoroughly.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Hi folks. I looked at the spiders more closely, and I do believe there is a bit of separation close to where it meets the cone on each of these. Please see these pics and let me know if that's correct. It seems like a bit of white starts to appear as I raise the cone. If this is the situation, what can I do? The second one is less obvious, but I think the same thing is happening (this is also the speaker with less friction). Thanks so much.
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Use Aleene’s Original Tacky Glue as the adhesive. You'll need to figure out how to best hold the spider in position in order to join the detached areas to the base of the cone. Best to sit the driver magnet down, so the cone and spider are in their relaxed position.
Do not use the drivers for 24 hours after the repair.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
I wouldn't advise attempting to repair the spider with any adhesive without cutting out the dust cap with an Xacto knife, being careful to avoid the voice coil wires, and using some shims between the voice coil and the pole piece. If they go the full length of the voice coil and pole piece it is possible that you could then glue/repair the tear in the spider and have it be back in alignment.
I learned this from the personal experience of attempting to cure an intermittent rub in my Mw6500s by gluing the spiders without any alignment. I think I may have just glued it into a cocked posistioning. Either that or the voice coils were cocked from the factory which I don't want to believe.
For shims I have used Vigoro plant labels which happened to be the correct thicknesses and very flexible.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
A great many have successfully repaired their detached spider without resorting to radical over the top surgery.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Sigh. Pissing matches always? I think that it is one thing to repair a tear in a spider but quite another to get the speaker to not rub anymore and in this case, and from my own personal experience, you want to try to ensure that you don't throw the baby out with the bathwater. Gluing the spider when the speaker is out of alignment may very well just glue it into a state of perma misalignment.
Cutting the dust cap out is nerve wracking the first time but then you see how easy it really is if you have steady hands of course, and good eyesight. If your eyesight ain't what it used to be, use one of those binocular type magnifiers that go on your head.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I'll bet you can't get out of bed without over thinking it.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thank you both for your replies. I'd of course rather do it without cutting out the dust cap, if possible.
Is it absurd to think that I could try gluing up without shimming the coil, and if it still rubs I could cut back the glued bit of spider and re-attempt it with shims? -
Cutting the dust cap off is simple surgery. Cutting the glued area would be foolish surgery. My advice stays the same. You will possibly see that the voice coil is misaligned at rest, ie. not even playing or being pushed manually and obviously gluing the spider in that state would be a mistake. The shims will align it. You can then run a ring of aleenes all around the spider/voice coil interface, in addition to where you have found that crack. There could be other places where it has been damaged and allowed the VC to be cocked.
You said it rubs badly so it is toast right now. That crack looks pretty small and there is probably something else going on which you will clearly see when you cut the dust cap off.
Here is what I ended up with after underthinking it and gluing a visible crack in my spider similar to yours. Voice coil is cocked.
Post edited by Gardenstater onGeorge / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
6510's and 6511's are all ticking time bombs with this issue. The minimum should be to remove dust cap, shim coil and then re-glue. You have a 50-50 chance that it is fixed if you just glue the spider as is.Don't take experimental gene therapies from known eugenicists.
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OK, this is all very helpful. Recommendations on a glue to reattach the dust cap? Also Aleene's?
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It's the doom and gloom twins back for another song and dance.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
OK, this is all very helpful. Recommendations on a glue to reattach the dust cap? Also Aleene's?
I was a bit nervous when I removed one for the first time. Aleene's dries crystal clear and if you are careful, I highly doubt you will know it's ever been apart.Post edited by joebass3 on -
It's the doom and gloom twins back for another song and dance.
Says the Boeing QC head.Don't take experimental gene therapies from known eugenicists. -
Well, I went ahead and cut the dust cap on the worse of the two drivers. I discovered that a section of the voice coil former had pinched up into the tube and was rubbing against the pole, as well as exposing the bottom-most winds of copper in the coil. These bits of coil had gotten bent out of shape and seemed worn.
I went to work pushing the bit of folded former tube back down and trying my best to gingerly form it back into a smooth circle, while pushing the coil back into place. The exposed coil ended up breaking. I don't know if there's any hope for salvaging this driver. I'm open to suggestions, but suspect it may be beyond my technical skill or level of commitment. I'm curious to hear anyone's thoughts.
Pics attached are of the pinched coil former before attempting to straighten it out, and after.
I will take a look at the second problem driver tomorrow. This one had less friction, so maybe more hope there for a simple spider glue job, or at least a less devastated coil former.
Thanks, everybody, for suggestions so far. -
Well done. Too bad on the outcome but it may have been irreparable, even if you had the magnet and T-yoke (pole piece) off the driver. Somebody played some square waves through that driver if you know what I mean. That voice coil got bottomed out hard against the back plate.
The best way to go in the future would be to try to get the magnet assembly off the speaker and work the voice coil former back into shape from the inside with something round and smooth like the rounded end of a sharpie marker.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
After sufficient caffeine it came to mind that a cocked voice coil (due to spider damage) could've allowed the VC former to snag on the top of the pole piece, causing the damage in that area.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Gardenstater wrote: »Well done. Too bad on the outcome but it may have been irreparable, even if you had the magnet and T-yoke (pole piece) off the driver. Somebody played some square waves through that driver if you know what I mean. That voice coil got bottomed out hard against the back plate.
The best way to go in the future would be to try to get the magnet assembly off the speaker and work the voice coil former back into shape from the inside with something round and smooth like the rounded end of a sharpie marker.
If it ohms out ok, then this can be done as I've done a couple myself. If it is mangled, it needs a new coil.Don't take experimental gene therapies from known eugenicists. -
Here's an update on my progress. I gave up on the first 6511, moving on to the second one, which was damaged in the same way, though a bit less severe, with the voice coil former having pinched up against the magnet pole.
I cut away the dust cap, worked the coil former back into shape and trimmed away a bit of the former cylinder that had started to tear. I did see that a loop or two of the coil was visible and loose below the former, but was not bent out of shape or worn down in the way of the first one I attempted. Once I got the former into shape, I did not notice any friction, so I'm hoping it stays happy at least for a while.
I moved on to the spider, applying glue all the way around the base of the cone and the innermost part of the spider.
Then I glued the dust cap back in place, weighting it down overnight with a socket.
I managed to find a single Monitor series 2 M4 locally on craigslist for $20 and harvested the 6502 woofer as a replacement for my thrashed 6511. Midwest Speaker Repair is recommending their 6502 clone as a replacement for the 6511, so I'm going with their advice here.
I pulled all the woofers and applied JB Weld (I was attempting to just get a nice clean bead on the front and rear of the magnet... you can see from my photo how well that worked out. This stuff is not the easiest to work with!)
Put it all back together last night. I've been trying to figure out what to do about an interconnect cable. For the moment, I just stuck bare speaker wire in the blade terminals and taped it to the cab to keep it in place.
So now I'm finally listening. They sound good! Soundstage is detailed, mids are especially satisfying. I would say it still sounds a little bit contained. I'm using some fairly old low end cable that I've been meaning to toss. Will see how an modest upgrade there affects things.
I also noticed a little static in the left channel when I first turned on the stereo, and there is a tweeter in the right channel that was scratchy through one or two tunes, but not at the moment. So I'll keep an eye on that.
Thanks again for all the hints. Any other thoughts are welcome. -
Good job. Those pics of the 6511's coils shows what happens on their saggy suspensions over time. The coil is impacting the pole-piece and damaging the aluminum former, releasing the copper wire. It will be interesting to see how long the repaired 6511 will last. I'd suggest not pushing the 6511 too hard. The 6502 is my go-to driver for 6511 replacement. I have swapped them in 3 different sets now. Better midrange and piece of mind that they won't implode when pushed hard.
Only other suggestion I have is to rebuild your crossovers.Don't take experimental gene therapies from known eugenicists. -
Nice work indeed. Perhaps keep your mirror imaged pairs balanced by replacing one of the 6511s in each one with a 6502, in the same geometrical position. I'm thinking the sensitivities could be different in 6502 vs 6511, even though it is probably subtle. The 6511 has twice the compliance and the 6502 only has a little higher BL but a little higher resistance.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Crown D150 amp
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
A 30 yr old 6511 has 3-4 times the compliance of an age-matched 6502
Don't take experimental gene therapies from known eugenicists. -
Put it all back together last night. I've been trying to figure out what to do about an interconnect cable. For the moment, I just stuck bare speaker wire in the blade terminals and taped it to the cab to keep it in place.
Does it have a pin/blade interconnect socket? I think the pin is used to carry the signal, not the blade.
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Oy veyPolitical Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Put it all back together last night. I've been trying to figure out what to do about an interconnect cable. For the moment, I just stuck bare speaker wire in the blade terminals and taped it to the cab to keep it in place.
Does it have a pin/blade interconnect socket? I think the pin is used to carry the signal, not the blade.
This is a blade-blade interconnect. I have a wire in each blade socket.
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Thanks for these suggestions. I will keep an eye out for suitable replacement woofers. Symmetry makes sense to me, and also insurance in case another 6511 fails. But apart from finding or making a decent interconnect cable, I don't have much of a budget for these. Wasn't looking, just happened across them for free, and I'm pretty content to have a pair this nice for almost nothing. Total investment so far = about $15 for adhesives, $20 for the replcement 6502, and a couple of late nights. Not a bad deal!
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Put it all back together last night. I've been trying to figure out what to do about an interconnect cable. For the moment, I just stuck bare speaker wire in the blade terminals and taped it to the cab to keep it in place.
Does it have a pin/blade interconnect socket? I think the pin is used to carry the signal, not the blade.
This is a blade-blade interconnect. I have a wire in each blade socket.
https://www.jameco.com/z/P-302H-CCT-Cinch-Connectivity-Solutions-Connector-Wire-to-Wire-PL-2-Position-Solder-Lug-Straight-Cable-Mount_248760.htmlPolitical Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk
