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B&W 803D crossover caps

I am considering an upgrade of the crossover capacitors in by B&W 803Ds, particularly the mid and HF coupling caps.

I took out the top bass driver to find out what caps were installed. It looks like for the diamond tweeter B&W uses a Mundorf Supreme silver/gold, 4.7 mfd 1200V. For the mid driver there are two; a 47 mfd Mundorf MKP 400V series coupling cap (in series with the driver) and a 10 mfd Mundorf Supreme siver/gold bypassing cap (parallel to the driver).

I was thinking about changing out all three, but have a few concerns.

I was going to replace the 10 mfd, 4.7 mfd Supreme silver/gold with Supreme silver/gold/oil. Would there be enough of a difference in these two types to justify the cost? I also do not want to make the upper end any brighter.

I am also concerned about the long term reliability of oil filled caps, as some failures have been reported in warmer environments. I wonder if B&W did not use the silver/gold/oils for that reason.

The biggest impact I suspect will come from the replacement of that series 47 mfd MKP. I would probably use either the Mundorf MCap EVO (Al metalization), MCap EVO oil (Al/oil), or the MCap EVO silver/gold/oil. All three are the same size for 47 mfd, and will fit to replace the MKP. Barring the issues about oil, which might be the best sounding? Again, I want to avoid too much enhancement of the upper midrange.
dhl93449
dhl93449 OP
455 posts
 
Oh, and one other point. B&W went with a Supreme SGO (10 mFd) as a bypass/parallel cap across the mid driver, but an MKP in series with it. I always wondered why they did this, but now realize that the series cap is in series with a very large outboard inductor (1.25 mH). So why spend a lot for a low inductance cap like the Supreme if you are going to put a large inductance in series with it? The parallel bypass cap, however, is directly across the driver so low inductance will pay off there.
dover
2,251 posts
 
From my experience with both Clarity and Mundorph caps the Mundorph S/G/O to Clarity is not a big jump and not worth the cost.

My recommendation, based on many crossover updates, would be to change the resistors to Duelund Silver Graphite first. This will improve transparency and more importantly in the context of your comments result in a much smoother sound. Steen Duelund is on record as saying that when upgrading crossovers with Duelund components you should start with his resistors.

Of the caps in the standard crossover I would only do the 47mF in the mid - probably a Silver/oil Mundorph which is a little smoother than the S/G/O.

Another option if you are keeping the speakers long term is to remove the crossovers and place them externally. Again I have found significant improvements in lower noise floor and less grain by simply removing the crossovers from the box.

Regards
dhl93449 OP
455 posts
 
Dover:

I would like to maintain the stock look if at all possible. Relocating the XO to the outside, well, you might just as well build the XOs from scratch then. No for me at this time. I agree that relocating them outside the cabinet would remove a lot of component vibration issues that XOs face while mounted inside.

The Dueland resistors will not fit the stock layout, as B&W uses radial lead (not axial lead) power tab type resistors with heat sinks. Their power rating of 100W is also way above any Dueland power rating.

Only an EVO 47 mFd SGO will fit. But I agree that one should be replaced first.
dover
2,251 posts
 
I have also used the Mundorph M-Resist (20w) with good results.
Have you considered redoing the crossovers on new boards with point to point wiring and better component layout to reduce interaction ?
dhl93449 OP
455 posts
 
Dover:

In a word, no.

I had only planned to replace a few caps, not rebuild the entire cross over. I don't think that a rebuild is sonically warranted at this point.

I am hesitant to replace 100W rated components with 20W versions, no matter what the sonic results MIGHT be. Perhaps with a 0.5 ohm resistor a 20W might work, but I have not done the power dissipation analysis to confirm.
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