B&W 803D crossover caps

Grannyring

Thanks for your input. Reinforced what I was thinking. The cost to do the swap to the silver/gold/oils would be about $1000 for both channels. Serious money.

I think I will stick with Mundorf at this point, as I want to maintain the character of the 803. The Dueland are stupid money and there is no place to put them without adding a lot of wiring inductance to the network. The Jupiter are about $500 more than the Mundorf for a complete swap sans the 47 mfd, and the 10 mfd 100V part is just a bit too long to fit on the crossover pc board. But looks like a serious contender for the 4.7 mfd feeding the diamond tweeter if I want to do that alone.

I also discovered that all the bass driver mounting screws were barely tight. Torquing those up made a large difference in the bass response. I also torqued the tension bar on the mid-range driver and that also improved sonics quite a bit as well. Freebes that didn't cost me a dime.

ptss

Do not worry. I have plenty of experience modding equipment. If you doubt it, see my post on mods for the Spectral DMC-10 in the WhatsBest forum.

BTW, my version is just the "803D". I have it on good authority that the later version "803 Diamond" uses only the Supreme Oil, not the SG or the SGO. This info was provided by looking at a replacement crossover for the Diamond version. Seems like that is a big step back, according to the only review I have found to rank all three Mundorf Supremes (humblehomemadehifi).

Call B&W regarding crossover caps? Are you kidding?

A simple swap out of a crossover caps is not rocket science. It will not damage the speaker or destroy my amplifiers. At this level of performance, the results will probably be very subtle, but that does not mean they are not worth doing.

Manufacturers often make design decisions based on cost as well as performance. We have an opportunity to re-evaluate that decision and remove cost from the equation, up to certain limits.

John:

Thank you for your thoughtful comments.

My goal is to remove a bit of upper midrange brightness without effecting resolution in bells, symbols, vocal microphonics. The speakers are not at all bad as they are, but could stand a bit of improvement in these areas. I well know from my experience modding amplifiers that improvements in certain components can improve the sound in seemingly small but still significant fashions. I have no hard and fast goal for the end result, but will probably know an improvement when I hear it.

A few other parameters. The replacements need to fit on the existing pc board without kluges or modifications. No running feet of extra wire from a remotely mounted component to the board. They cannot reduce the reliability of the speaker by leakage of oil or wax. And finally there is cost. Given the value of the 803Ds I don't feel like spending $5000 on caps.

I was using the extensive review of humblehomemadehifi for initial evaluations. That review does not place the Clarity MR above the Supreme SG, but I realize there is probably a degree of subjectivity (to each his own). The Jupiter caps are highly regarded, perhaps above the Mundorf line.

As I posted above, it looks like B&W may have stepped back in SQ for the later Diamond series. They may have had a reason for using Supreme Oils (Al metallization) instead of the more expensive SG as in my D version, but I suspect it may have been more cost driven than SQ driven.

Regarding the other components, from my BOM documents on the 803D, the resistors are part number RNP50s, which are 100W, 5% power film resistors (TO247 package) that are clipped in to heatsinks on the CO board. They are made by MB Electronics in Germany. The resistor in series with the diamond tweeter is either 0.5 or 1.0 ohm (there is a contradiction between the value on the BOM and the schematic). The resistor in series with the midrange FTF is 100W 2.0 ohm RNP50s. My suggested replacement would be a Caddock MP900 power film resistor, which has a tighter tolerance and better tc, same TO247 package.

The inductors look like nothing special. Air core, conventional wire wound, wire gauge 1.2 mm (not flat ribbon).

It seems to me the most important cap is the 47 mFd midrange FTF coupling cap. But here we are limited severely by that capacitance. Mundorf has a Supreme EVO SGO that is 47 mFd, but it costs $700-800 and is too large to fit. The next closest are the EVOs I cited above. Bypassing is possible, but probably not that effective as this driver is crossed over at 4KHz, and a bypass would be kluge at best.

The next is probably the diamond tweeter coupling cap at 4.7 mFd. The Jupiter will fit as well as perhaps the Clarity

And yes, I considered re-wiring as well. But not for now, as that requires a complete strip down of all the drivers, and I want to avoid removing that FTF midrange if at all possible.

Ptss:
Sorry if I misinterpreted your comments. Mine were based on an experience I had a few years back with B&W regarding a delamination problem I had with some 804s speakers I had. The finish on the top of the speaker (Cherry) was splitting and cracking and I felt this was a manufacturing defect but B&W would not agree. They were arrogant and condescending which left a bad taste in my mouth. They also tend to believe that their engineers have the last word in innovation and if they did not think of it, well then it will not be an improvement. Ergo I would be loath to contact them about any potential component replacement as I can pretty much predict their response.

You mention JBL and I was going to point out that I also re-built the crossovers in my JBL L212's, as well as the power amp in the sub. I did not use crazy audiophile components (just good Dayton polypro caps and air core inductors) and the sonic results were amazing. I had previously modded these by mounting the drivers on solid walnut plates to time align them. That mod is documented on the JBL Lansing Heritage site (under DHL or DHL93449 no sure which) a few years back.

http://www.audioheritage.org/vbulletin/showthread.php?32862-Modded-and-restored-JBL-L212-speaker-system

http://www.audioheritage.org/vbulletin/showthread.php?33993-L212-Sub-amp-rebuild

The post on the WB forum is under the Spectral Manufacturer's section of the forum.

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

John:

I wanted to thank you publicly for generous offer. I will try those Carity caps when I get them.

John:

The more I look into this and the more reviews I read, the more opinions differ.

Looks like the 47 mFd will probably be the Mondorf EVO. Al/oil or SGO I am not sure yet. Some say (ie Tony Gee) that the Al oil are better for midrange which is the application here. On a purely material basis, I prefer the use of silver metallization over Al due to it's conductivity. No one else makes a cap this size that even comes close to fitting.

For the Diamond tweeter coupling cap, I could use the Clarity MR, as it is very reasonably priced. I cannot find anyone with stock on the 630V part, only the 400V part, which Parts Connexion carries. Do you know of any stocking dealers for these? Any opinion about 630V vs 400V? I have heard one should use the highest voltage rating is a series (Tony Gee again).

I would also consider the Jupiter for this application if it weren't for the very high cost of these ($520 pair). If I don't like them, I may not be able to re-sell them if they have been soldered in a circuit. I was speaking with (Jerry??) at Jupiter and he was very knowledgeable, but had no direct experience of the copper foil/wax units being used with B&W diamond tweeters. He also made mention that a source he knows (that likes to cut apart caps to see what's in them) tells him Mundorf "oils" actually have no oil in them. I find this surprising, but perhaps they use extremely small oil films that are not easily detected.

Rtilden:

Based on your experience, did you find a material difference between the Mundorf M-Cap Supremes vs the SGO? I understand the "Supremes" do not contain oil, so my quandary is still SG only vs SGO vs silver oil vs "no oil". I still do not quite understand the use/impact of oil in the first place.

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.

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:

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.

Ptss:

I can see the potential benefit to moving the XOs outside the box. My early JBL L212 had the crossovers outside of the enclosed driver housings.

Vibration from the drivers will definitely influence the inductors and capacitors in the network, simply "gluing" them to the pc board with lumps of RTV or caulk may not be that effective.

But practically speaking (no pun intended) moving them outboard of the 803D also has it's pitfalls, as you end up with longer speaker wiring between the drivers and the XO, with the accompanying increase in inductance and resistance. Not to mention the ugly appearance. The bass XO is huge, with monster 100 mFd Mundorf polypropylene bypass caps. Placing that outside would look butt ugly IMHO.

Bypassing caps...not sure what they buy you in a crossover. I know folks use them to "tweak" the sound but I have never played with them for that. I would rather buy a single cap with the right dielectric and low ESR in the first place if at all possible. Plus, from a technical viewpoint, things like dielectric adsorption cannot be remedied with parallel caps; only ESR or maybe ESL. The frequency range in a speaker crossover (maxing at maybe 30 KHz) is just not high enough to see a resonant frequency shift by using a 0.1 mFd cap in parallel with a 5 or 10 mFd coupling cap in a tweeter XO, for example.

So for example, the B&W diamond tweeter is crossed at 3500 -4000 Hz. The reactive impedance of the 4.7 mFd coupling cap at 4KHz is about 8 ohms. It would only be 0.8 ohms at 40 KHz! The 4.7 Mundorf has an ESR that is about 10 milli ohms or .01 ohms, still 10 times lower than the capacitive reactance at 40 KHz. Now what good is placing a 0.1 mFd cap in parallel with the 4.7? It would have a capacitive reactance of 50X the 4.7 (at 40 ohms) and who cares what its ESR is, because that would be swamped with the capacitive reactance.

If you are parallel connecting a series of lower value caps that may make sense if you cannot get the total value in a single cap (like a teflon or polystyrene, for example).

Stoni:

Interesting post. I have been looking at what B&W has been doing with these cross overs in the last few product iterations. Particularly with the capacitors, they have been all over the map, except with that 47 mFd MKP, which is consistently used from the 804S through the 803D2/3.

In my 803d (first diamond in the series), the tweeter coupling cap is 4.7 mFd Mundorf Silver/Gold Supreme (not oil). In the 803D2, they went to Supreme Oil (Al metallization?), not Supreme Silver/Oil or Silver/Gold/Oil. Looks like in the D3 they are using Supreme SGO at 5.1 mFd, not 4.7 mFd?

I have decided to try the EVO SGO 47mFd in the midrange. The Al/Oil is cheaper but I prefer silver metallization. I have also decided to replace my Supreme 4.7 mFd S/G with a Supreme 4.7 mFd SGO. If that is too strident, I will consider a Jupiter copper paper/oil, but I am nervous about the longevity of these paper/oil caps (along with the cost).

I also have a pair of 804S, with the Al tweeter. That product uses almost the same values as the 803d. The tweeter coupling cap is Mundorf 4.7 mFd Supreme, and the midrange (which is the same unit as in the 803) is coupled with that MKP 47 mFd, and bypassed with a Mundorf Supreme 10 mFd. Like the 805, the bass drivers are bypassed with an electrolytic parallel with a film (150 mFd electrolytic parallel with a 47 mFd MKP film). In the 803D, the bass drivers are bypassed with two 100 mFd MKP films.

I agree with you that bypassing an electrolytic with a film in a cross over is not a good idea. I think that is because in a XO, the caps see significant AC voltages. Any dielectric adsorption effects in an electrolytic cannot be reduced by a film in parallel, and may therefor may be audible.

Over the last few days I have had a chance to complete the mods to my crossovers. Thanks to all for their suggestions.

I had to remove the upper bass driver and the mid range FTF driver to get at the crossovers and the wiring. I also removed the tweeter but I will get to that challenge below.

The XOs are mounted on plastic standoffs that are a bear to release the PC boards from. B&W slops glue on top of the barbs that hold the boards to the standoffs, and getting all the glue from the barbs usually means destroying the barbs. I contacted B&W and their CS was kind enough to send me back ups (they are not listed in their parts lists). I ended up pulling the two front standoffs and replacing them with a threaded insert designed for wood. My local hardware store had some that fit the .280" holes perfectly (use 5/16", for #8 screws). With .25" tall spacers, these mounted the boards perfectly.

The HF XO board is mounted on the roof of the midrange chamber, the MID XO is mounted on the floor. To remove the HF XO you have to release the board from the standoffs, then cut a number of tie wraps to release all the wiring. The HF XO is fed with two 12 ga wires (red/black) terminated in gold plated tab connectors (nice). Another pair of 12 ga black/red are soldered to this board and are terminated in a Molex connector that feeds the tweeter. I did find many of the tab connectors to be very loose, so I had to correct that before re-connecting.

I ended up swapping out the Supreme SG 4.7 mFd for an identically sized Supreme SGO. I also pulled the 0.5 OHM tab power resistor (no name on it) and replaced it with a 0.75 OHM 1% 100W MP9100 Caddock thick film resistor that mounted to the OEM heatsink perfectly. I used 0.75 OHM instead of the 0.5 OHM to reduce the tweeter output slightly. B&W originally spec'd a 1.0 OHM which they changed mid production to 0.5 OHM.

For the MID XO, I also swapped out the 2 OHM resistor with a 2.0 OHM 1% Caddock MP9100. I pulled the MKP 47 mFd Mundorf film cap and replaced it with an EVO SGO 47 mFd. This cap also fit quite nicely. I had PartsConnex match a couple to under 1%.

After re-mounting the XOs, I soldered all the gold plated tab connectors to the wire they were crimped to. Unusually, some were soldered by B&W and some were not. B&W also used some sort of grease on the connectors (not necessary for gold connectors IMHO) so I removed that as well. I pulled all three bass drivers to tighten and solder connections.

Now the tweeters. I strongly suggest most users leave these guys alone. They are extremely fragile and you must not touch that diamond diaphragm if at all possible. In mine, I felt a little too much front to back play, so I thought something might be loose. The motor unit/diaphragm is coupled to a bar that runs rearward through the end of the casing tube. At the end of this bar, a soft, gooey gasket material (looks like Sorbothane with the consistency of a gummy bear that has been on a hot sidewalk) surrounds the bar and isolates it from the casing. When you pull the motor and bar forward, you inevitably destroy this gasket as it sticks like crazy to the bar, and turns itself inside out as you pull forward. So order a backup from B&W before you disassemble the guts of the tweeter.

In my tweeter, the plastic coupling nut that holds the bar to the motor was loose. And you cannot tighten this nut unless you pull the guts of the tweeter out.

After all was put back together, I had a chance for some preliminary listening. I have to say the total end result was more pleasing than I anticipated. If I have to use a single word, it would be "smooth". Edginess on horns and vocal sibilants was gone. Bells and symbols are now slightly recessed in volume, but still very clear in position, with more 3d space between them. The overall sound fill left to right is vastly improved, with sound spilling outside the boundary of the left and right speakers (something I have been struggling to get with these 803d's for some time). The midrange seems to be separated better from the bottom end in clarity (this is hard to describe), so the bass transients no longer "mask" some of the midrange, as they had done before.

All in all, I am very happy with the changes.

edwyun

Because that route is fraught with just as many variables and complexities. I was going to do that with another previous set of speakers and ended up buying the B&Ws instead.

To do what you suggest  first you need 3 to six power amps, depending on if you use stereo or mono amps. You need to adjust the output levels of each amp with each driver, so you need an RTA/pink noise setup to do it right. Then you need a decent XO setup. Anyone know of discrete component class A XOs that have three XO points? And a choice of first, second, or third order slopes? No? Me neither.  There are XOs out there, but most are op-amp based which is unacceptable to me. Finally, if you are using B&W drivers, you have to have impedance and parameter data for the drivers which is unobtanium unless you measure it yourself.

As I stated I considered building my own speakers prior to buying the B&Ws, and was going to go the full active route. But I could never get over the compromises and costs, plus I cannot design a cabinet like B&W does. 

Mark:

You're welcome. They are sounding exceptional right now. That 47 mFd EVO SGO midrange coupling cap is really making a difference.

georgehifi:

I don't think I suggested there is a quality issue with the parts in the crossover, but a cheaper MKP version will not sound the same as a Silver/Gold/Oil. That is why they make the SGO in the first place. Do you even have 803Ds or have listened to them?

Replacing that MKP 47 uFd with a SGO did make a significant difference in sound quality. Neither capacitor sounds "bad", but the SGO sounds better, and isn't that what we all strive for? If every manufacturer had the tuning of their product perfect out of the box, then there would be no upgrade market then, would there?

Since my original post I have added a few more mods. I now believe the upper midrange harshness that sometimes is present is sourced from the FST midrange driver. There is a mod that the 800/802 series had (a heavy cast iron weight attached to the back of the FST driver) that is absent from the 803 series. When I asked B&W tech support why the 800s have this but the 803D does not, they told me the weight will not fit in the 803 cabinet, but it will fit in the marlan cabinet on the 800/802. So not entirely believing their story, I ordered two to see if I could fit them. I had to remove a small pc of 1" of foam at the back of the cabinet (so tech support was correct) and the drivers and weights fit fine. You have to make another threaded tension rod (I used 6mm stainless threaded rod) and obtain a couple of 6mm SS nylok nuts; one set to attached the rod to the FST driver, and another set to hold the weight snugly against the back of the driver. Don't forget there is a rubber gasket placed between the weight and driver. You may also need loktite between the threaded rod and the FST driver to keep things tight and to prevent loosening. This mod also worked quite well in smoothing the upper midrange even further.

What I would really like to get a hold of next is the latest version D3 midrange driver. They are completely different from the older FST and from what I understand, have addressed many of the problems of the earlier version. But, they are not available on the B&W parts website yet (maybe the never will be).  

biggy79

I don't think george reads your posts carefully. You are correct, there is a 'bypassing" cap (ie one parallel to the FST driver) in the crossover network. It is a Mundorf silver gold or silver gold oil, depending on what product you have or version of crossover. It is an upgrade (at least according to Mundorf, who makes these capacitors) over the any MKP version, which is in series with the FST driver.

The EVO versions are the only ones that will fit (47 uFd) as a substitute for that MKP 47 uFd. They will improve the sound considerably, although at very high cost. I do not understand, from a sound quality perspective, why B&W would use an MKP version instead of an EVO (either oil or SGO). From a COST perspective, perfectly understandable.

Don't forget the series coupling resistors in the MR CR network. The service manual shows a couple of values being used (and mine had even different values). Plus or minus 0.5 ohms in this coupling resistor can make a significant difference in the 800-1.2 KHz region.

The changes from 47 to 51 uFd in the D2 may not have anything to do with "smoothness", but a shift in crossover frequencies due to driver changes from previous versions. 

With respect to the "woofer" caps (there are two MKP 100 uFd in PARALLEL with the four drivers), remember these are there to roll off the bass drivers at higher frequencies. I don't think Mundorf makes 100 uFd SGO caps, and as these are there to attenuate signals across the woofers, their impact on sound quality is minimized (unless you have an lower midrange peaking problem). My tests with pink noise do not show any such peaking (nor do I hear one), so I leave these alone. I have heard of people "bypassing" these with lower value (like 1-10 uFd) SGO type caps, but I doubt if you gain much, because the frequencies (and impedance) needed to impact bass drivers. For example, a 10 uFd cap will be lower than 4 ohms at frequencies above about 4 KHz. That is quite a bit higher than the 200 Hz cross over frequency for the bass drivers, so these bypass caps will have little to no impact on the bass drivers at or below the crossover frequencies. 

george- download a version of the service manual from B&W and check out the crossover schematics before you comment.

There are various differences in the tweeters in the 800/802/803 series products. Whether some sound "better" than others may be a matter of personal taste or sensitivity.

George:

Regarding parallel caps. I agree in general, except when there is no or limited choice. For example, when an Al electrolytic is used as a coupling cap at the output of an amplifier driving low impedance loads. A polypro or film cap may not be available or practical to use in that application if DC offset from the amp is an issue. Adding a parallel poly pro film cap will definitely improve the sound over just an electrolytic alone. 
I believe one reason that parallel caps are not a panacea is that certain properties (like poor dielectric adsorption) cannot be compensated for by placing caps in parallel. 
One practitioner of massively paralleling film caps (John Curl of Parasound) has recently commented that that practice (seen in many early Parasound power amps) may not be best. He cites resonance effects between these parallel stacks at extremely high frequencies (100's of Megahertz) as the issue. Those early power amps still sound pretty good though.

biggy

That is what I did. Silver gold Oil 4.7 uFd for the coupling tweeter; 47 uFd EVO SGO for the mid coupling cap; SGO 10 uFd for the mid bypassing cap.  
Whether you use SGO or just "oil" (those are aluminum metallized instead of gold/silver) is a matter of personal taste (and budget). I never found SGO "harsh" or "bright". Maybe you can try the "oil" version first, since they are much lower cost. I just think the silver/gold metallization is lower impedance since gold and silver are much better conductors, but the aluminum may be applied by Mundorf in a thicker layer, which compensates for lower conductivity of the metal itself. Specs wise I don't think there are major differences, but longevity wise I think the gold/silver are better.
As far as the resistors go, you will have to see exactly what B&W put in your crossovers. As I said, they vary by production year and model. I substituted Caddok MP9100 series for the versions used by B&W; they are a pin/pin exact replacement, and fit in the pc board holes (and on the heatsink) precisely. I would avoid the exotic resistors that will not fit on the pc board. Running long wires to mount these can undo the benefits of them in the first place. Plus, you need to replace the OEM parts with versions that have the same or better power rating.

biggy:

Regarding sizes. Check a website like parts connextion. Not all "EVO" sizes are the same, and the "Supreme" (black) versions are larger I think. I used the " 47 uFd EVO silver gold oil", in the white cases with gold printing. The "Supreme" versions have special, non-inductive windings and are therefor actually two caps in the same package, therefor much larger. I don't think a EVO Supreme SGO is available at 47 uFdf. 

" 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. 

George:

You miss the point. I just explained that film caps are often not an option when the manufacturer is using surface mount technology for the components. Plus, the proper size poly pro film cap will physically not fit in a 1U chassis and is extremely expensive to boot. Polyester (mylar) caps are smaller, but are not as good as polypropylene.

biggy:

I am currently using all Silver Gold Oil Mundorfs; either Supreme versions (TW coupling, MR bypassing) or EVO (not Supreme) versions (MR coupling), except for the bass LF crossovers, which are bone stock. As mentioned, the harshness I believe is from the FST MIDRANGE, not the tweeter. If you want to de-emphasize the tweeter, you can increase the resistor in series with it. Replacing that MKP 47 uFd with EVO oil or EVO SGO will make a major difference, so I would start there and then listen to the results. I would not go in and wholesale replace multiple caps and resistors. Adding the anti vibration weight from the 800/802 can make another significant difference. You can see this in the midrange driver replacement video on the B&W parts website.

I put little importance into those cap reviews that rate plain "oil" with Al metallization with silver or silver/gold. Too many variables that may or may not apply to my personal system. When I have compared oil vs SGO in preamp outputs and DAC outputs, I have always like the SGO. 


As I said, try the "oil" versions first and see if you like them. They are the cheapest version and if they are better for you than SGO, then you are ahead of the game. But be aware that swapping these caps is not easy, and pulling and re-installing the crossovers is time consuming.

"Sorry no you confused the discussion, you said amp (see below) and I said amp and then you bought preamps into it. Most of us with the knowledge know that many sources and pre’s have much smaller coupling caps than what would be on the output of an amplifier. "

Last time I checked, "preamps", line amps, and power amps are all species of the genus "amps". You are the one assigning the term "amp" to Power amps. 

The point being that there are numerous amplifiers using electrolytic coupling caps in the output, not just tube power amps. Substituting a film cap for these electrolytics may the best sonic solution, but not considered practical by the manufacturer.

Phasey??? WTF is that? Are you implying putting two polypro caps in parallel create abnormal phase response in a speaker? Can you point to where this has ever been measured or shown mathematically? If these high end audio caps are supposed to be closer to ideal caps (the purpose of their manufacturers), then there should be no such behavior in their performance, singly or in parallel.

Erik S:

Last time I checked, a few years ago, Jupiter did not make a copper film cap in 47 uFd to replace that critical midrange coupling cap. Clarity cap makes one in their CSA line, but that is metallized poly pro. It is 62 mm diameter (much larger than the 50 mm diam EVO and the 42 mm MKP), so it may not fit on the MR CO board. Plus, I doubt if those CSA versions are any better than an OIL or SGO Mundorf. In general copper film caps are too large to fit or are not available in high enough capacitance. And of course, we dare not parallel smaller values for fear of the dreaded "phasey" smearing effect.

I also need to say that in general, with 90% of the music I listen to, the modded B&W 803D I have sound wonderful. There is some material, mainly compressed rock (like in my case Genesis Trick of the Tail/CD ,not vinyl), that sounds harsh. I do not ascribe to your description of these speakers whatsoever, and I have had numerous friends and strangers listen and they find the results impressive (some are musicians). So I am happy with them for the most part, but continue to look for ways to improve them if I can.