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Mystery Capacitor and the Tangent RS4 Crossover

 I have a pair of Tangent RS4s whose crossovers I am currently in the midst of trying to rebuild (Early 80s British 2 way speaker). I used to power them in the 80s with an Adcom GFA1 amp (200 watts/channel which I understand both Bob Carver and Nelson Pass had a hand in designing back when Adcom was based in New Brunswick, NJ, my old home town). Apparently, either time or I did a fair amount of damage to those caps (probably both) and some are hard to id, particularly one that looks like a piece of pink sugar coated candy with green, white and violet stripes? I'm working on a schematic for this crossover so I can get some expert opinion on the project and maybe id the capacitor value by process of elimination. But I am new to this and am learning as I go. If there is anyone out there interested or who could lend some assistance I would be happy to share/learn.
I set out to simply replace the caps but am beginning to question the design and wonder if it could not be improved upon. For starters it seems to have a lot of caps for a two way crossover (8 in five styles), plus 2 resistors and 3 coils. Modern designs I have looked at typically have two or three caps for 2 two way crossover.The drivers and cabinets are in good shape and I have always liked this speaker which sports a 200mm Audax bextrene cone woofer and a 19mm KEF t27 dome tweeter, housed in a nicely crafted 42.5 liter walnut veneered mdf cabinet, all of which has held up amazingly well over the yearsI'll try to figure out how to post pictures to this site if anyone is kind enough to offer assistence.
Ag insider logo xs@2xbruce19
oldhvymec
5,101 posts
 
The stuff I read...Pink fish. caps..

If you want to save yourself a lot of time and buy a lot better XO call parts express, their cheepo 2 or three way will be a LOT better XO than the
1-4 versions I saw. OLD crossovers like that are easy to better just because of  much more accurate parts and lower prices..

Rebuild if you like, Normally when you see a pile of caps like that in a two way, it was because the parts are SUPER cheap to BUY, it doesn't mean the parts are not of ok quality at the time.  The builder cut cost by doing it that way.. Maybe even tuned left to right. If the two XOs are different looking, they may have tuned left to right.. VERY rare.. VMPS did it..
No two driver are the same.. Close but back then... Never.. Seas maybe..
Even Infinity settled for production XO.. left the same as the right.. Junk compared to today's stuff..

Regards
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bruce19 OP
249 posts
 
Many Thanks for the thoughts from all of you! By way of update, I acquired a LCR meter and tested the mystery cap and all the others and now am pretty confident. Many thanks also to Josh of Madisound.com who was most helpful!
I have made a schematic of the crossover which is available here if anyone is interested:https://drive.google.com/file/d/1CKneJ4wmWGvH751mDj8dha9Ma1dkNmqm/view?usp=sharing
Perhaps it will save some time for anyone else with this speaker looking to recap.Ps- Erik I'm eager to look at that Xsim but first I have to dig out my old windows computer.
timlub
2,040 posts
 
You've got 12/18 slopes with impedance compensation on the woofer and frequency compensation on the tweeter.  
imhififan's avatar
imhififan
2,203 posts
 
it seems to have a lot of caps for a two way crossover (8 in five styles), plus 2 resistors and 3 coils. Modern designs I have looked at typically have two or three caps for 2 two way crossover.
According to your schematic, seems like you can use a single 3uf film cap to replace the 10uf, 2.25uf, 1uf and 0.47uf.
timlub
2,040 posts
 
@imhififan   ..... Quick question for you.  I don't know this tweeter, so I have to ask. Have you seen the impedance curves of this tweeter?  Are you considering the inductor to ground? Are you considering the 3 ohm resistor in series?  
Not being  familiar with the impedance curves of this tweeter, these questions need to be asked. 
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