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Polk SL200 Tweeter Magnet Shift?

thesteve

thesteve

Active Member
So I picked up my eBay Polk Audio SDA 2B Studios today and quickly found the problem that I'm glad they developed. This post describes them: https://audiokarma.org/forums/index.php?threads/scored-some-sda-2b-studio-fixer-uppers.977407/

The seller inherited them in some kind of deal gone bad and unloaded them in a no-reserve auction ($76).
So aside from the obvious missing cross-connect cable that the guy didn't know about, the left tweeter magnet-shifted. Luckily my receiver has an overload protection that kicked in when I turned up the volume.
I suspected the tweeter, but I didn't expect it to have the classic magnet problem as Polk woofers from that era.

I don't have high hopes on repairing said tweeter, but I figured I'd ask the experts before potentially destroying it in a first attempt.
I did a search but came up with zero results on tweeter magnet shift. The coil still reads close to 8 ohms surprisingly.
Thoughts?

Oh yeah, I'm glad I asked the seller if they were Dayton Audio passive radiators. He turned around and came back with a Dayton Audio box (I was right) and in the box was one of the original "fluid coupled" subwoofers!
So I only have to find one SW121 on eBay now. (I asked about the other one and he reacted kinda like maybe he threw it out... he didn't actually answer but I didn't interrogate him further.)

IMG_3431.jpg
IMG_3432.jpg

You can see how the magnet is totally eccentric. A bit tougher to see in the dome picture, but you make out how the coil's pinched in the same quadrant.
 
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I fix shifted magnet Polk drivers for the Polk forum. I've seen (and fixed) a couple shifted SL2000s. It happens. You can fix it (if the voice coil is OK)!

I'll attach some pics from the last one I did. You'll need to use shims to get the top plate centered.
 

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Wow that's awesome, what a quick response!
I'll research things more slowly now that I know it's possible and make sure I do it right.
As an update, the tweeter wasn't the overload issue I was (am still) having. I tried again with the tweeter removed, and although I hear sound from both channels (hard to tell if the dimensional array woofers are working but I'll worry about that later) when I turn up the volume, my overload protection still kicks in. This is only on the cabinet with the bad tweeter. Oh well, I guess there's something funky in that crossover.
Looks like I've got an official project on my hands here!
 
I don't see a problem with that tweeter other than the SL2000 sounds like crap.

Without the SDA cable the SDA drivers will only play below 100Hz.
 
Update. ALL FIXED!
Turns out the tweeter is actually good!

So there was a dead short at the input terminals.
I thought for sure it was a 20 uF electrolytic in the crossover (read as shorted). But after cutting a lead the cap was fine and the short at the input remained.
Well the whole crossover board was mounted diagonally. I still haven't looked at the other side to see if that's how it should be... anyway, I cut the zip ties to it to have a look and checked the resistance again with the board pulled back.
Read 7 ohms. I was irritated that it wasn't 8 like the other speaker, so I figured I'd put the tweeter back in the circuit to see if that was why.
Well I hooked it back up to my receiver (which has a handy pink noise feature for each channel) and brother that tweeter is fine!

Now I'm wishing that guy had the other subwoofer... I would have been all done for the night!
Well I'm still happy. So far zero dollars extra and I'm almost done.
Thanks, Mr. Law. I might have ruined that perfectly good SL2000 without your quick post.
 
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Thanks F1nut. You are correct, sir. We were both typing at the same time.
I already have a make-shift cross-connect cable in the mix and I believe everything is working.
I heard about the upgrade involving new tweeters... I'll definitely put it on my wanted to buy list.
Thanks folks!
 
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The correct terminologies as this will help you in the future.
Mid-driver not woofer.
SDA cable not cross-connect.
Passive radiator not subwoofer.
 
F1nut said:
I don't see a problem with that tweeter other than the SL2000 sounds like crap.

Without the SDA cable the SDA drivers will only play below 100Hz.
Click to expand...


I recall seeing a thread, where some guy on this forum argued that the SL2000 sounded better than the upgraded later tweeters designed by polk.

Forget the guys name, but wonder if he will chime in?
 
kevintomb said:
I recall seeing a thread, where some guy on this forum argued that the SL2000 sounded better than the upgraded later tweeters designed by polk.

Forget the guys name, but wonder if he will chime in?
Click to expand...
If one can't hear above 12kHz then the SL2000 might sound acceptable.
 
I spent some time this afternoon perusing this post:
https://forum.polkaudio.com/discussion/182943/the-tale-of-5-tweeters-sda-tweeter-replacement-guide
Very informative. My favorite line was on page 3, "After listening to my stock 8Ts, the original tweeters, SL2000, have a coloration that sounds like crumpled Mylar potato chip bags when reproducing scratches on records."
That said F1 makes a good point. I'm not 20 anymore and actually, when I was 10 or so a firecracker went off close to my ears and did some damage.
My left ear to this day is noticeably less sensitive compared to my right. An easy test is holding up a ticking watch to both ears.

Anyway, for the record, that magnet is horribly off center, it wasn't parallax or the camera lens. I guess the gap is not very tight at all and allows for lots of leeway.
 
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The SL-2000's that came in the Monitor 10's I have didn't sound all that bad, but the RDO-194's I replaced them with did make a difference for the better. The 194's are smoother while still being nicely detailed sounding.
 
Not to interrupt the discussion, but I thought I'd close the loop on what was wrong.

For whatever reason, the plastic standoffs went missing some time in the past and someone tie-wrapped the crossover board directly to the choke and shorted things out.

I found some packing foam and made a nice spacer. Everyone likes pictures, so:
IMG_3439.jpg

I also found a like-new SW121 for $50 on eBay. Now I just have to replace the missing screws that the guy threw away (he tried to use a resonator that only used 5 screws that didn't match up at all).
Good news is I can sell those (Dayton Audio DS315-PR) and more than make up for the cost of the replacement SW121.
 
thesteve said:
I spent some time this afternoon perusing this post:
https://forum.polkaudio.com/discussion/182943/the-tale-of-5-tweeters-sda-tweeter-replacement-guide
Very informative. My favorite line was on page 3, "After listening to my stock 8Ts, the original tweeters, SL2000, have a coloration that sounds like crumpled Mylar potato chip bags when reproducing scratches on records."
That said F1 makes a good point. I'm not 20 anymore and actually, when I was 10 or so a firecracker went off close to my ears and did some damage.
My left ear to this day is noticeably less sensitive compared to my right. An easy test is holding up a ticking watch to both ears.

Anyway, for the record, that magnet is horribly off center, it wasn't parallax or the camera lens. I guess the gap is not very tight at all and allows for lots of leeway.
Click to expand...
The only thing off center is the label.
 
thesteve said:
Not to interrupt the discussion, but I thought I'd close the loop on what was wrong.

For whatever reason, the plastic standoffs went missing some time in the past and someone tie-wrapped the crossover board directly to the choke and shorted things out.

I found some packing foam and made a nice spacer. Everyone likes pictures, so:
View attachment 2395310

I also found a like-new SW121 for $50 on eBay. Now I just have to replace the missing screws that the guy threw away (he tried to use a resonator that only used 5 screws that didn't match up at all).
Good news is I can sell those (Dayton Audio DS315-PR) and more than make up for the cost of the replacement SW121.
Click to expand...
You've done well to find that PR.
 
Lavane said:
The SL-2000's that came in the Monitor 10's I have didn't sound all that bad, but the RDO-194's I replaced them with did make a difference for the better. The 194's are smoother while still being nicely detailed sounding.
Click to expand...
Came here to recommend the RDOs.
 
I set up a saved search.
Once I get my new passive resonator and set these babies up I'll be able to do an A/B comparison to my Monitor 5As with Peerless tweeters.
I guess its apples and oranges though.
 
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