B&W 803D crossover caps

Ptss:

If you are referring to the Spectral posts, there are three parts because WB forum had a limit on photos per post.

Here are links to all three parts:

http://www.whatsbestforum.com/showthread.php?18147-Spectral-DMC-10-mods

http://www.whatsbestforum.com/showthread.php?18148-Spectral-DMC-10-mods-part-2

http://www.whatsbestforum.com/showthread.php?18149-Spectral-DMC-10-mods-part-3

Rtilden:

I am kind of where you were at. I would like to make a change, but not really mess around with a lot of trial and error swapping stuff in and out. If I could have gotten a general consensus that a particular option was a no brainer improvement, I would have gone that route.

But now it looks like that is not the case so I will probably stick with two mods, the 47 and the 4.7. For the 4.7, I will try the Clarity MR in comparison to the stock Supreme SG. I would like to also try a Jupiter copper/wax/paper but the cost of entry is quite high.

Regarding the 47 I hear what you say but a stack of three parallel caps just will not fit. So practically I am left with the EVO or EVO/Al-Oil or EVO SGO. The EVO Al-oil was suggested by Tony Gee's review but I am actually leaning toward the SGO. Since the EVO Al-Oil is not that expensive, perhaps the reasonable thing to do is to try that first, then maybe the SGO. Then once the mid range choice is selected, try the Clarity MR in the tweeter 4.7 position.

Supremes have a real advantage technically over the EVO in that they are two series capacitors interwoven, which reduces the series inductance of the overall capacitor. The EVO is a conventionally wound single cap, but is more compact because it is not really 4 caps in one like the Supreme.

What I cannot rationalize from a fundamental POV is what difference the materials combos make. Aluminum metallization with and without oil vs silver metallization with oil vs silver/1% gold with and without oil. Clearly silver and silver gold are much better conductors than Aluminum, but the metallization thickness matters too. The silver/gold should have a better (lower) DF if the metal was a better conductor, but Mundorf's DF data do not support this. So maybe the Al films are much thicker than the Ag/Au, offsetting any advantage in bulk conductivity.

I suspect the gold is added to the silver to reduce any tendency for corrosion of silver. Silver is not really that "noble" in that it easily forms chlorides and sulfides (tarnish), and these may be formed by chloride or sulfide impurities in the oil (or in outside air contamination if it gets into the cap). Gold, even in small percentages, may reduce the tendency to form these compounds. That is why I prefer the silver gold alloys from a basic longevity perspective, although people's impressions of sonic performance are another matter.

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.

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

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.