Need some help with Thiel CS3.5 crossovers - diyAudio
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Old 25th February 2013, 03:30 AM   #1
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Default Need some help with Thiel CS3.5 crossovers

I've noticed some issues with my 3.5's recently so I decided to pull the woofers and take a look at the caps. Low and behold I have a couple blown caps. I intend to recap them myself. However there are some components I don't recognize. Next to each group of caps there is a silver cylindrical component that I'm not familiar with. The only labeling I see appears to say H15000 nohm 15000H. Here is a pic Click the image to open in full size.

If any of you folks could identify that for me I'd really appreciate it.

Also, is there any reason to suspect or replace the coils or resistors while I've got the crossovers out of the cabinets? Any recommendations for caps? Obviously this is my first time doing this and I appreciate any help you guys can offer.

Thanks a ton!
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Old 25th February 2013, 03:47 AM   #2
Einric is offline Einric  United States
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I think they are a polyester or polycarbonate bypass capacitor.
I have seen them used in OOOOOLD RF equipment at my old shop.

Last edited by Einric; 25th February 2013 at 03:53 AM.
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Old 25th February 2013, 01:16 PM   #3
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thanks for the reply Einric. I'm going to pull a couple and see if I can come to any kind of consensus on capacitance. Of course they're 25 years old, so that may be a chore. Any chance these are fixed value inductors? That would seem to be odd in a crossover (from the little I've seen) but a 15000nh inductor would be about that size? There is one that appears to have been damaged when the cap next to it burst and its construction appears to be a coild of foil type substance. Past that I'm still guessing. I've sent an email to Thiel to see if they would identify them for me.

Thanks again!
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Old 25th February 2013, 04:17 PM   #4
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Per Thiel they are 15pF polystyrene capacitors used for their ultra high frequency filtering ability. Learn something new every day!
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Old 25th February 2013, 07:31 PM   #5
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Basically, the large value non-polar electrolytics are being bypassed by 1uf metallized polypropylene ("MKP" type, 400VDC, though 250VDC replacements would work just fine) and 15pf polystyrene (replacement value not critical, just make them all the same if you replace them). The original MKPs are made by Solen, but the Dayton brand from Parts Express would also work as replacements. You can get Bennic replacement non-polar electrolytics and Solen MKPs from Madisound. Personally, I would recap both crossovers with identical parts keeping all values the same. The coils should be fine as well as the resistors, but you can measure the resistors easily to check.

I have a set of CS3.5s in daily use, fantastic speakers with the right amp. A crappy amp just won't do, believe me, night and day with a good amp. I've got a good stock of spare parts for them I've accumulated over time. If you don't mind, take a look at the pics I've posted of an extra crossover I have and let me know if your values are the same.

I do know that Thiel used Dynaudio D28AF and D28/2 for the tweeters and two model numbers for the Scanspeak mid-woofer (mine are 13M8521, but I bought a pair from someone once and they were 13M3808, physically very similar, maybe even identical). I'm curious to know if there were any variations to the crossover. I can't say for sure what tweeter was used with this crossover (probably D28/2), but the mid woofer was definitely 13M8521. S/N is 4331 on this crossover.
Attached Images
File Type: jpg left thiel 800.jpg (171.2 KB, 73 views)
File Type: jpg thiel marked up 800.jpg (128.5 KB, 67 views)

Last edited by DreadPirate; 25th February 2013 at 07:40 PM.
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Old 25th February 2013, 10:01 PM   #6
Einric is offline Einric  United States
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Wouldn't 15000H be 15000pF with H tolerance?
That would be 15nF correct?

Either way I don't think these would have failed in 30 years, I suspect they are fine.
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Old 26th February 2013, 02:46 AM   #7
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Dread my midrange drivers are 13M8521 and are original. One of them is on the way back to Thiel to be rebuilt. My tweeters are D28/2 and are replacements provided by thiel about 5 years ago. My crossovers appear identical to yours from the components right down to the construction.

On a side note, what the heck did Thiel use to glue the conductors in place? It took everything I had to get those things out and I pretty much destroyed them in the process.
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Old 26th February 2013, 12:47 PM   #8
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Adhesive looks to be black E6000.
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Old 26th February 2013, 09:07 PM   #9
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Einric can you explain to me what H tolerance is? Again, showing my inexperience.
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Old 26th February 2013, 09:24 PM   #10
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Dread - the black adhesive used to glue down the caps and resistors does look like E6000. I'm wondering what the clear adhesive used to glue down the coils and the hook up wire is. It looks almost like hot glue, but is much stronger. May be a thick epoxy of some kind.
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