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.
For example, when an Al electrolytic is used as a coupling cap at the output of an amplifier driving low impedance loads.
This kind of amp cap coupled output is very rare to have. I take it it’s tube with no output transformer, but with capacitor coupling instead, I would just get an OTL myself but??

For and 8 ohm speaker you would need at least 2000uF for the coupling cap to see low fr limit of -3db at 10hz.
One or a couple paralleled depending what polarizing output voltage this amp has of these would fine great with NO! bypass cap.

or you could get cheaper Black gates instead.

Cheers George

I found here http://www.audiokit.it/it/30951-condensatori-mundorf (I am from Italy) there is a 47uF Supreme EVO Oil, which measures 76x67 mm.

The 47uF standard M-Cap EVO Oil measures 50x50 mm, the same as your EVO Silver Gold Oil.

Do you think the extra 26mm thickness of the Supreme Evo can make it not fit in?

Maybe if Stoni (see the 12-09-2015 10:27pm post) could use the Supreme EVO Oil into his 803D2 the same could happen in our 803D ...

The M-Cap Evo Oil is available at 100uF, so if I use the EVO Oil in series with the midrange maybe I could put woofer and midrange (coupling) caps of the same type (like in the original project!) even if you told me woofer caps don’t make significant difference in sound, but there would be a theorical coherency between bass and mids, both with EVO Oil instead of MKP, and the same thing would happen between mid (bypassing) cap and tweeter (coupling) cap, both with Supreme SGO instead of Supreme SG.

I am also thinking of removing all silver from my speakers, and "downgrade" from the Supreme SG to the standard Supreme for coupling tw cap and bypassing mid cap: warmer, richer and more natural sound, with absolutely no emphasys on the treble and upper midrange.

Maybe If I do, I would transform the B&Ws in other speakers and I don’t want to, but I would be happier.

Hard choice

B&W itself did "downgrade" from Supreme Silver Gold to an "inedited" Supreme Oil, without silver, and the general consensus is the 803 D2 sounds much better in the treble range than the D, much smoother (and still not enough...maybe the problem is Mundorf?).

I don’t know if replacing a silver cap with another silver cap, but with oil, is worth the money an the work; @dhl93449 please, I ask you to tell me the changes you had in hf so I can have some elements to make my decision easier (better to say less hard).

@stoni chaged the B&W custom 51uF Supreme Oil in his 803D2 with SGO, then he had to make another work to change tw cap again (with a Jensen Duelund if I remember well), it is clear he was not satisfied from the upgrade (iscit a real upgrade, with these diamond tweeters?) from an (aluminium?) oil cap to a silver gold oil cap, since the latter highlights high frequencies and may mask the other parts of the spectrum.

In a well tuned and high quality system (in mine, electricity and source are near to state-of-the-art, with a power regenerator followed by isolation trasformers for each machine and a divine Accuphase DP700 SACD player, cables are near to the best Cardas ever made, Luxman 509u integrated is not the best amp in the world but if you read Uday Reddy’s Soundstage! 2009 review maybe you may hurry to find an used one, or to buy the new 509x) a SGO capacitor could sound without harshness afterall.

Don’t misunderstand me: I don’t listen now with harshness in the highs (only some selected albums make me struggle, for example Genesis’ "Selling England by the pound" or Joe Satriani’s "The Extremist", and I know even these albums could sound better, and all the music with them), I have simply reached speakers limits and I want to go on in my audiophile journey of (personal and equipment’s) improvement.

Another idea could be to use the Supreme EVO Oil in all positions: 4.7uF tw coupling, 47uF mr coupling and 10uF mr bypassing, and EVO Oil on the woofers.

Or 4.7uF Supreme Evo Oil in tw coupling and 10uF in mr bypassing, Evo Oil both in mr coupling (47uF) and in woofer caps (2x100), to make something similar to the original project of both D and D2.

The only truth is one should have to try, not reasoning "on the paper" ... !

I had a change in my system I did not tell you until now...
A (deplorable in my opinion) technician repaired my Purepower putting inside it Claritycap SA caps instead of the original taiwanese Fu-Jack caps (they seem Panasonic or Vishay clones) without telling me before, maybe because he had that caps in stock, without need for ordering a 10uF 500V (for the power stage, right after power inlet) Panasonic and a 2uF 600V (for battery recharge system) Vishay caps.
Now I have the impression of a tonal shift towards mid-highs.

The Humble Honemade Hifi comparison tells the Claritycap make sound shift towards clarity, since Panasonic is the most neutral cap in its range, it does not highlight anything.

Do you think I have to make another technician replace the Claritycap SA in my regenerator with Panasonic and Vishay (since there is no Panasonic cap under 10uF), and only after that to think at speakers recapping?

Many thanks
" This kind of amp cap coupled output is very rare to have. I take it it’s tube with no output transformer, but with capacitor coupling instead, I would just get an OTL myself but??"

Not as rare as you think. Did you know the Bryston BDA-1/2/3 all have Al electrolytic (surface mount) coupling caps in their outputs? Along with I think their preamps, even current production. Their engineers are concerned with the small amount of DC offset their class A discrete amps produce (10 - 20 mV), ergo the caps. Using a 10-30 uFd film coupling cap is out of the question for them, as it's size and cost would be prohibitive.

Bryston does not parallel a film cap with these Al Elct caps in the output stages, due to the lack of compact surface mount film versions (poly pro are very rare in surface mount), and NPO ceramics are outrageously expensive. 

In my new BDA-3, I removed the Elect caps and put in a surface mount shorting bar. The small DC offset is easily handled by my Parasound JC2 preamp and its DC offset servo controllers. Made a significant difference in sound quality. I have been in contact with Bryston Eningineering and urged them to put in DIP switches so that users have the option of shorting out those caps if they have downstream circuitry that can handle the offsets. 

Not as rare as you think. Did you know the Bryston BDA-1/2/3 all have Al electrolytic (surface mount) coupling caps in their outputs?

I said amps, they are preamps, and yes many preamps and sources are cap coupled, but they don't need anywhere near the size cap an amp does so one only good quality film cap will do them, again never by-pass them.

Cheers George