lance G Posted November 14, 2019 Report Share Posted November 14, 2019 Greetings all, A newby from the U.K. here asking for some re-assurance regarding my (somewhat guided by this site/forum) choice of capacitors. The speakers are some 40 years old now, and although in super condition for that age, still have the originally fitted OE capacitors (and fortunately drivers). I have been assured (by the supplier) that the cap's as listed below will be fine for the AR9's, however I harbour some uncertainty regarding the lower voltage ratings of the supplied cap's when compared with the original specification voltage ratings. This is where I seek the reassurance from you AR experts ! I am not at this stage too concerned with the poly/electrolytic debate (I have an open mind), but am happy to initially try to retain the original sound as much as possible (with electrolytics), I can play the capacitor "upgrade" game at a later date, although I fear therein may well lie madness ! The nearest alternative option I could find in the U.K. were Alcap branded with much closer voltage ratings, but I felt after some research that the Mundorf may be a better choice (other than the voltage concerns). Title Label Unit price Quantity Total (ECAP70-030) - 2.2uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-030) £1.18 4 £4.72 (ECAP70-060) - 3.9uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-060) £1.41 4 £5.64 (ECAP70-050) - 3.3uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-050) £1.33 2 £2.66 (ECAP70-070) - 4.7uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-070) £1.48 2 £2.96 (ECAP70-130) - 22uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-130) £3.71 6 £22.26 (ECAP70-140) - 33uF 70V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP70-140) £4.45 2 £8.90 (ECAP50-040) - 82uF 50V Mundorf ECap AC PLAIN electrolytic capacitor (ECAP50-040) £6.69 2 £13.38 Subtotal: £60.52 Shipping: DPD Courier - Trackable & Secure (1 day) - Recommended : £4.95 Subtotal excluding taxes: £65.47 UK VAT: £13.11 Order total: £78.58 Please see the note (as sent with the order) below; For Acoustic Research AR9 (pair). To replace Elcap bipolar electrolytic with Mundorf E-cap; From 100V 4uf (to 70V 3.9uf). 50V 6uf (to 70V 2.2+3.9). 100V 8uf (to 70V 3.3+4.7). 100V 24uf (to 70V 22+2.2). 50V 30uf (to 70V 33). 50V 40uf (to 70v 22+22). 100V 80uf (to 50V 82). Hopefully these will be correct for my needs ? If you might have any concerns with the selection please let me know ! Kind regards, Lance. As a footnote, thank you to all of the contributors to this forum. I have found it to be a fascinating source of reading. Hopefully I can contribute something in the future which may be of help to other members. Lance. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 14, 2019 Report Share Posted November 14, 2019 Welcome to CSP Lance. It's always nice to hear from our friends across the pond. That's basically what I did with my 90's (see link below) I did try and choose caps that were closer than what I could get with the ECap on the 30 and 40uF. For the larger caps you could parallel some large Bennic NPE. For the 470uF you could use a 250 + 220 and for the 2500uF a 500 + 2x1000. I'm not sure that 50V 80uF will be robust enough. Perhaps others could chime in. The original is 100VAC. Quote Link to comment Share on other sites More sharing options...
lance G Posted November 14, 2019 Author Report Share Posted November 14, 2019 Hi David, Thanks for the prompt reply. I had previously seen your extremely useful post and took on board your findings to a great degree, thank you. Congratulations on the satisfactory outcome by the way. I had a pair of 90's many years ago, loved them, but circumstances dictated an eventual, most reluctant sale. I did also always hanker after the 9's and the opportunity recently arose allowing me to "scratch the itch" so to speak. I have the capacitors, previously listed, in hand as of today so am keen to fire up the soldering iron and get started ! Apparently there are some slight differences between the 90 and 9 crossovers (3 way/4way). I will say that at this stage I am not looking to change out the low range 2500u and 470u cap's at the moment. My understanding is that they hold up somewhat better than the majority of the other cap's which relate to the LM UM and HR drivers, and these LR cap's are on the bottom board so should be more readily accessible for future attention. I am also more concerned about the ongoing health of the LM UM and HR drivers (sounds like expert talk this, but I can assure you I am no expert !). I think I have gone down a somewhat similar route to yourself with the signal cap's, other than the 80u where I proposed to use the Mundorf 82u rated at 50v (DC as I understand). As you point out the original cap' was 80u at 100v AC, I think the 50v mundorf actually would come out at circa 35v AC (50v DC/1.414=35.35v AC ?), and although I have been assured that this particular cap will "be fine", like yourself I have some retiscence and would appreciate some re-assurance from someone (anyone) better qualified than I. The above MIGHT appear as if I know what I am talking about, but much is based upon internet research and a loose knowledge of some electronics. Just for information I am currently driving them with a couple of Quad 606 amplifiers. Bi-amped, one amp' for the woofers and one for the upper drivers. I understand that the 9's need power and would hope that these amp's would be considered adequate by the AR afficianados. With this in mind I am further mindful of all components being of adequate suitability. I believe some of the drivers are becoming more difficult to source (even more so in the U.K.) so want to reasonably "protect" them from any damage. I am most happy for anyone to chime in with any related comments. Any information should hopefully be of benefit. If anyone wants any information from my side please just ask. As I said the speakers I have appear to be highly original, likely U.K. assembled since some of the cap's have "made in UK" markings. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 14, 2019 Report Share Posted November 14, 2019 3 hours ago, lance G said: Apparently there are some slight differences between the 90 and 9 crossovers (3 way/4way). Both are 4 way speakers. The only difference is the woofer size 10 inch vs 12 inch. The difference in the xover is a 350uF woofer shunt cap vs 470uF and the addition of a tank circuit 2500uF in the AR9. My 10Pi speakers have the 2500uF and one was within spec the other was not. I have yet to test any in my AR9s. I did find that all of the metal canned caps in my 90's were reading high and the black/red end pvc caps were still in spec BUT they produced a dull sound. The xover from the LMR/UMR and tweeter are the same except the 90's are wired out-of-phase. Quote Link to comment Share on other sites More sharing options...
lance G Posted November 14, 2019 Author Report Share Posted November 14, 2019 Apologies, (3 way/4way) of course you are right, I should have recalled the 90's being 4 way. Thanks again for the reminder and further clarification. The 470u cap' is I believe the blue one in the picture. A poor picture but it was a quick snap for some basic perusal after the first opening of the cabinet/s. I rotated the picture, hence the odd perspective, in an effort to view the poorly focused "made in UK" on the red, I believe to be 80u cap. The visible black and red 30u ? Elcap is one that I believe really needs to go sooner rather than later. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 14, 2019 Report Share Posted November 14, 2019 The red cap should be the 80uF. The black with red ended pvc cap should be the 30uF. I've seen this cap in this style and as a metal can cap. The 470 should be the blue cap. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted November 14, 2019 Report Share Posted November 14, 2019 Concerning the Mundorf E-Cap voltages. The E-Cap spec sheets don't disclose much info, but I've written Mundorf, and the U.S. Mundorf rep, concerning their voltage rating. Both responded with basically the same comment, "to not worry about the voltage. We've never experienced a blown E-Cap in the field". Not a response to inspire confidence. Though, I've used E-Caps without issue. But, I also add 400V film & foil bypass caps, to any electrolytic I use, and I'm sure that adds some extra power handling capability. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 14, 2019 Report Share Posted November 14, 2019 1 hour ago, Stimpy said: I also add 400V film & foil bypass caps, to any electrolytic I use, and I'm sure that adds some extra power handling capability. Nope. It makes it the lower of the cap voltages. Still 70VDC and 50VAC When 2 capacitors are connected in parallel, the voltage rating will be the lower of the 2 values. e.g. a 250 V and a 400 V rated capacitor in parallel will have a maximum voltage rating of 250 Volts, as the voltage is the same across both capacitors, and you must not exceed the rating of either capacitors. Working Voltage, ( WV ) The Working Voltage is another important capacitor characteristic that defines the maximum continuous voltage either DC or AC that can be applied to the capacitor without failure during its working life. Generally, the working voltage printed onto the side of a capacitors body refers to its DC working voltage, (WVDC). DC and AC voltage values are usually not the same for a capacitor as the AC voltage value refers to the r.m.s. value and NOT the maximum or peak value which is 1.414 times greater. Also, the specified DC working voltage is valid within a certain temperature range, normally -30°C to +70°C. Any DC voltage in excess of its working voltage or an excessive AC ripple current may cause failure. It follows therefore, that a capacitor will have a longer working life if operated in a cool environment and within its rated voltage. Quote Link to comment Share on other sites More sharing options...
lance G Posted November 14, 2019 Author Report Share Posted November 14, 2019 Hi Stimpy, Thank you, that is a most re-assuring reply, exactly the sort of thing I was hoping to hear. I have also been following your re-capping exploits (along with DavidR's), and have also found them to be a great source of reference. There is little substitute for actual experience, and I am grateful for the benefit of yours (and DavidR's). Good to hear that you wrote to both Mundorf and the Mundorf rep', although the replies might be considered to be a little technically vague ?! Great stuff. I would imagine other forum members will be interested in that particular nugget. I had also been told verbally by the supplier that the cap's I ordered would "be fine". Also I had no response to my note sent with the order that, should there be any concerns as to suitability for them to let me know. I have currently decided to press on with the upper boards cap's, hopefully over the coming weekend, but will try to further check with the supplier tomorrow, specifically regarding the 82u 50v LMR signal cap before I press on with the bottom boards. Quote Link to comment Share on other sites More sharing options...
lance G Posted November 15, 2019 Author Report Share Posted November 15, 2019 Spoke to the supplier today, most specifically regarding the (ECAP50-040) - 82uF 50V Mundorf ECap AC PLAIN electrolytic capacitor which is intended to replace the originally installed 80uF 100v ac cap'. I was assured that there will be no issues because any operating voltage actually experienced will not reach anywhere near the rated capacity. So I guess all in all that's good enough for me. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 15, 2019 Report Share Posted November 15, 2019 53 minutes ago, lance G said: I was assured that there will be no issues because any operating voltage actually experienced will not reach anywhere near the rated capacity. How do they know what you have for an amp. 35 VAC is the rated capacity. If you have a current pushing amp maybe not but if you have a tube amp or an old SS amp you probably will. Quote Link to comment Share on other sites More sharing options...
ar_pro Posted November 15, 2019 Report Share Posted November 15, 2019 This is the AR-9, arguably one of the best systems ever built by Acoustic Research, so why consider installing a capacitor that doesn't meet factory spec? Quote Link to comment Share on other sites More sharing options...
lance G Posted November 15, 2019 Author Report Share Posted November 15, 2019 Fair comment, and I would love to be readily able to source an 80Uf 100v ac bipolar electrolytic capacitor here in the UK, and at real world realistic cost. Indeed I would love to install new (original but of course they are not available) exactly on spec' capacitors throughout, to preserve the integrity and original sound as much as possible, but it does not appear to be that straight forward ! I really would appreciate positive advice and answers from anyone in an effort to achieve (or as near to) this. I believe a lot of people spend a lot of time modifying and fine tuning their own speakers to their own personal liking. I do however, absolutely, think that if these speakers are capable of being as good as they are purported to have been upon introduction, and have been alluded to since, then theoretically there is quite some merit in restoring them to their original specification, again apparently not something that is currently straightforward to do. Perhaps it would be advantageous to many AR owners if as an exercise someone knowledgable could compile an up to date reference list/database of all the neccessary, CURRENTLY AVAILABLE, components needed to restore an AR9 (that would make it easy for me !), AR90 or any other valued vintage AR speaker to as near to original condition as possible. Now I am really getting carried away ! I will endeavour, as much as within my capability, and at the mercy of current circumstances/availability, to restore my speakers to as near original as I can. Anything is only original once, any change and it can NEVER be 100% original again. I am feeling my way with this "project", please be kind to me ! Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 15, 2019 Report Share Posted November 15, 2019 Seems that the tops for bi-polar/non-polar electrolytic caps made today are rated 100V and that's DC rating; so the AC rating would be approx 75VAC. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted November 16, 2019 Report Share Posted November 16, 2019 The discussion regarding this voltage issue is very interesting. The AR-9 schematic that I am viewing shows a total of nine caps with voltages rated at 50, 60, and 100 volts - - I assume these are all DC ratings. Regarding the Mundorf E-caps, it should be noted that these are available in two versions: PLAIN and RAW. As I understand this, the principal difference is in the configuration and treatment of the foil dielectric. The OP is looking at the PLAIN caps - - - these have a smooth dielectric and tend to be considerably larger and more expensive, in general. The RAW caps have a roughened etched surface on the foil dielectric which results in a dimensionally smaller cap, and less expensive. I would think that an AR aficionado in the UK would have multiple sources for German-produced Mundorf caps, and I would suggest you seek out the 100VDC RAW version where you might be concerned with this particular specification. On 11/14/2019 at 2:34 PM, Stimpy said: "We've never experienced a blown E-Cap in the field". Not a response to inspire confidence. Stimpy, I'm a bit perplexed by this remark of yours.... but not the company's statement. If you've been in direct contact with Mundorf and their U.S. rep, exactly what type of response would inspire confidence for you? Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 16, 2019 Report Share Posted November 16, 2019 17 minutes ago, ra.ra said: I assume these are all DC ratings They are VAC as indicated on the caps. This makes more sense as it is an AC circuit and the caps don't pass a DC voltage but will hold it. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 16, 2019 Report Share Posted November 16, 2019 And another tid-bit of info to ponder. The 4 and 24uF caps in my 91 were Callins as they are in the 90 and 9. They are rated 50VAC yet look identical. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted November 16, 2019 Report Share Posted November 16, 2019 David, you clearly understand electronic circuitry far above my pay grade, but I am unsure what point you are driving here. I was merely pointing out that the Mundorf-E cap is available in more than one format regarding product construction and voltage ratings, in my attempt to be helpful to the OP's primary concern. Are you prepared to say that the 100VDC Mundorf E RAW caps will not provide suitable results for the OP's project? If so, could you please clear up this ongoing confusion, and specify which voltage ratings (AC and DC) for replacement caps will be suitable for our restoration projects? 1 hour ago, DavidR said: They are VAC as indicated on the caps. I do not see that info presented in this thread - - could you please present pics to confirm this, and also back up this argument with original AR documents with these voltage specs? Also, when I take a close look at your AR-90 thread, I think I see 24uF caps rated at 100VAC. What am I missing here? Quote Link to comment Share on other sites More sharing options...
Stimpy Posted November 17, 2019 Report Share Posted November 17, 2019 On 11/15/2019 at 7:56 PM, ra.ra said: Stimpy, I'm a bit perplexed by this remark of yours.... but not the company's statement. If you've been in direct contact with Mundorf and their U.S. rep, exactly what type of response would inspire confidence for you? Less politics, and more actual measurements, in this case, would inspire confidence. Something showing peak power handling. While component measurements don't describe sound quality, they would at least help demonstrate real-world wattage capacity. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 17, 2019 Report Share Posted November 17, 2019 On 11/15/2019 at 9:38 PM, ra.ra said: What am I missing here? The AR-9 schematic that I am viewing shows a total of nine caps with voltages rated at 50, 60, and 100 volts - - I assume these are all DC ratings. A 100VAC does not equal a 100VDC rating and vice-versa. The RAW Mundorf caps are less suitable than the Plain. RAW are rated for 35VAC-100Vdc, (ECAP100-Raw), MLytic® Bi-Polar AC Electrolytic Capacitor. Plain ECap 70 are rated for 50VAC-70Vdc, (ECAP70-Plain), MLytic® Bi-Polar AC Electrolytic Capacitor I haven't run across any NPE caps made today that are rated for 100VAC. Unless the stated VAC rating is R.M.S. and then you can apply the 1.414 factor to arrive at a max value. I'm also not sure if the AR VAC rating is R.M.S. or MAX rating. I used several Mundorf ECap 70 in my 90's and have pounded them somewhat hard with no issues but my SS amp is a current pusher (500 Watts Per Channel into 4 ohms). Quote Link to comment Share on other sites More sharing options...
lance G Posted November 17, 2019 Author Report Share Posted November 17, 2019 Thanks to everyone for their input so far. Back to basics. My speakers are circa 40 years old and have the original crossover capacitors/components. I am of the understanding that it would be wise to replace (at least) the capacitors which as I understand it are all bipolar electrolytic. I want to restore them to original specification (if possible!). I cannot find exact replacement capacitors as they do not appear to be available anymore. My understanding is that there are a total of 9 capacitors in the network/s mounted on two boards. Information taken from an ACOUSTIC RESEARCH AR9 CROSSOVER NETWORK circuit diagram found on this site. Apparently a mix of ac and dc types. Two capacitors on the LF network, WHICH I AM NOT INITIALLY LOOKING TO ADDRESS, (more fun for later !). Two cap's on the HR (high range/tweeter) network; 4uF 100VAC signal and 6uF 50v series signal ? Three cap's on the UMR (upper midrange) network; 24UF 100v signal, 40Uf 50V shunt ? and 8uF 100VAC shunt ? Two cap's on the LMR (lower midrange) network 80uF 100VAC signal, and 30Uf 50V shunt ? I have used the terms shunt and series signal for some of the cap's, I am unsure as to what the correct terms would be ?! I perceive that the quality of the signal cap's takes some precedence. I have searched the internet in depth, including this site (the best resource) and have, perhaps mistakenly narrowed things down to a selection of capacitors which I have ascertained (and to some degree been led to believe) would be most adequate as a solution. I have always harboured some concerns (never mind the uF matching!) regarding the matching of the voltage ratings and whether some capacitors may be subject to an application of over voltage. I have been assured by the supplier of the capacitors (listed in my first posting) that "because the capacitors are in a crossover network they will never be exposed to voltages approaching anywhere near their rated values". I believe the 70v (DC?) rating of the Mundorf E-cap's (plain foil) equates to circa 50 VAC and are plain foil is considered best for audio signals. I believe the higher rated Mundorf RAW cap's (100V DC ?) are actually rated at 35 VAC and are frowned upon as being less good than plain foil for audio signals. I can get alcap brand cap's (close to the original elcap, as replacements) but the highest V rating of only some of the "more suitable" of these are at 100v which for the signal cap's would still only equate to circa 70 VAC ? I guess that's where I am at the moment. If it is true that "because the capacitors are in a crossover network they will never be exposed to voltages approaching anywhere near their rated values", then I guess there will not be a problem and the cap's I have in hand will do a sterling job ? I also take on board stimpys findings (thank you !). Can anyone tell me roughly what maximum voltages the crossover networks are likely to experience ? What maximum current is likely to arrive at the speaker terminals ? Quote "Each of the two sections of an AR-9 (that is, the woofers and the upper range) may be used with an amplifier capable of delivering 400 watts continuous power (800 watts total continuous power per speaker) being driven to clipping not more than 10 percent of the time on normal music source material". My AR-9 speakers are currently bi-amped with two Quad 606 amplifiers (140 watts into 8 0hms), one driving the woofers (as above max' 400 watts) and one driving the upper drivers (again, as above, max' 400 watts). Can someone please tell me if my selected capacitors are up up to the job ? I don't want to damage/destroy any of the upper drivers ! I still feel I only have a somewhat loose grasp of the above, if it is erroneous in any regard please don't "rip me to bits". I am very happy to be corrected and open to any constructive criticism ! Thanks again. Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 17, 2019 Report Share Posted November 17, 2019 12 minutes ago, lance G said: Two cap's on the LMR (lower midrange) network 80uF 100VAC signal, and 30Uf 50V shunt ? I have used the terms shunt and series signal for some of the cap's, I am unsure as to what the correct terms would be ?! Series and Shunt are correct terms. The 30uF is after a coil that filters out most of the frequencies that are 'unwanted' for that driver. The 30 shunt cap doesn't see that much duty because of the coil and is there to shunt any 'leftover frequencies to ground. The 4 and 6 caps are wired in series and forms (I believe) a 2nd order electrical circuit offering more protection to the tweeter. My only concern was the 80uF cap voltage rating. Quote Link to comment Share on other sites More sharing options...
lance G Posted November 17, 2019 Author Report Share Posted November 17, 2019 On 11/16/2019 at 1:29 AM, DavidR said: And another tid-bit of info to ponder. The 4 and 24uF caps in my 91 were Callins as they are in the 90 and 9. They are rated 50VAC yet look identical. Not sure how similar the networks are but those uF values in the AR9 are rated 100VAC for the 4uF and 100v for the 24uF. Now that is what is stated on the diagram ! Maybe it's time to for me to "pop a woofer out" and try to see what is actually marked on the cap's ! Quote Link to comment Share on other sites More sharing options...
DavidR Posted November 17, 2019 Report Share Posted November 17, 2019 The 9 and 90 xover for the tweeter and UMR/Mid are quite different from the 91 but the cap voltage rating is typically to protect the driver but maybe they were assuming a lower powered amp for the 3 -way. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted November 17, 2019 Report Share Posted November 17, 2019 Wow. That's a nice recap (no pun intended). Well stated, and which proves that you have a better than "loose grasp" of the subject at hand. While I can't really address power handling, since I don't listen loud, I don't think you'll experience any issues. Many of the vintage speakers that I've rebuilt, or seen rebuilt, used capacitors with a 50V rating. Those held up for decades. Also, power handling is an additive thing. All components add to the speakers capabilities, including capacitors, inductors, resistors, and finally drivers. So, don't worry too much about the E-Caps. They're not the only part exposed to wattage. And regardless how I feel about their published specs, I like and use E-Caps, and have never had any fail. Finally, speaking of E-Caps, you can also use Jantzen Audio Premium Elko caps. E-Caps and Elko caps are made by the same manufacturer. They should sound similar. The Elko caps are available in some values different than E-Caps, which might help in the rebuild. Parts Connexion sells both NPE brands. Good luck, and Thanks for the shout-out...! Stimpy Quote Link to comment Share on other sites More sharing options...
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