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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.
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erik_squires
16,118 posts
 
There are definitely times when you want to do a complete speaker analysis.  Infinity speakers, old Yammies come to mind.

One thing to keep in mind is that we used to use a lot of bypass capacitors because big films were too expensive, and achieving good results was cheaper with big electrolytics and small films in parallel.

In any event, the proper way to go about doing this is to measure each driver's electrical and acoustic properties, in place, and simulate the crossover using something like XSim.  I encourage you to go over to the DIYaudio forums where people snack on these issues all day and you can post pictures.

Best,

Erik
noromance's avatar
noromance
9,811 posts
 
This might help:
https://www.electronicshub.org/capacitor-color-codes/#Capacitance_Color_Code_Table
jasonbourne52's avatar
jasonbourne52
2,863 posts
 
Don't alter the component values of that crossover! Those values were chosen by extensive listening tests by the designer! Only replace the electrolytic caps with similar values of new poly caps. You can replace the two inductors (coils) with air-core types - if the originals are solid core. But again the replacements' values must be equal or very close to the originals - to maintain proper phase and amplitude response between the woofers and tweeters.
jasonbourne52's avatar
jasonbourne52
2,863 posts
 
I owned a pair of the Tangent RS2's back in the 80's. Excellent speakers. if a bit too "British" - laid back! Well, they are not JBL's!
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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