B&W CM10 Mystery Cap?

I own a great pair of B&W CM10s, low to high seems to be how B&W prioritized parts quality across LF to HF crossovers. LF begins with an average electrolytic, then into the HF which also covers off the mids - they step it up to a mystery film cap, on to beautiful Mundorf SilverGold Oils for the tweeter.

I suppose on some level this is the way to do it, if one were a manufacturer, but leaves me thinking there is improvement to be made and mids are my target. I was thinking of placing a 0.1uF bypass cap on the yellow mystery cap as a safe bet for a boost and thinking Mundorf Supreme SilverGold.

Here is a pic of the mystery cap in question - what do you think of this plan? Good? Or scrap it and just replace the cap with something expensive and be done with it ?





what mystery cap? i dont see any mystery cap. That component with heatsink is probably a resistor. The yellow one is probably for the mids high pass filter. 

That’s great Erik, appreciate that! I’ll have a look.

BTW, I thought further about your comment on my JBL thread - electrolytic replacement with film and ESR. What have you done to typically mitigate that? In LF applications dial down the capacitance slightly?



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@rickysnit As I tried to write, you compensate with another resistor.

That is, if your cap’s ESR goes from 0.4 to 0.2 Ohms, you must add the missing value with a new R so the

new ESR + R = original ESR

I like to use Mills here because the high wattage are tiny compared to other brands, and extremely precise values. Get at least a 5W resistor.  If there is already a resistor in series you may chose to replace it instead with a larger R.  Say your original values were:

0.4 ESR + 0.2 R = 0.6

but now you have

0.2 ESR + 0.2 R = 0.4

You could either add another 0.2 R or replace the original with 0.4 R so the total remains 0.6.

OP:  Also, the compensating resistor is MOST important going to ground.  It's not as critical and maybe trivial in series with drivers. 

i added the Mundorf, at first a little underwhelming but given a few days they've opened up - does that make sense in a bypass scenario?? It's a neat trick, still unsure if as effective as complete cap replacement, but seems like a worthwhile experiment nonetheless!


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