lance G

£ or $ or something else ? As with all things I guess it would very much depend upon condition and an ability to function. Any pictures possible ?

I don't know how many others are following this with interest, I know I certainly am. Hats off !

I know this is a very old post, I have just come across it while trawling back through some fascinating historical postings. I am wondering, should the ac power conditioner aspect be of even more importance in these modern times ? It is now a more common practice to use powerline adapters to transmit signals/data on the ac line of our domestic electric supply. This for our internet enabled devices, T.V's and the like. We do this ourselves in our own homes, but would/could the supply already be compromised in this manner before it reaches our homes ?

Hi Giorgio, thanks for the supportive reply and your further input. I do think it may be worth anyone bearing in mind where appropriate the available length of the flexible wiring between the connectors and the cone. Especially if there is a perceived issue with sound quality. The connectors are on a small insulated plate which can be subject to an element of rotation (perhaps by knocking accidentally ?) which results in a lengthening of one wire, unlikely to be an issue, but of more concern the shortening of the opposite wire which could cause the issues I have experienced. This would tend to be proportionally more relevant to larger drivers where they experience a larger range of travel. I do think that the problems I have had stem from when the driver was manufactured, as in my opinion the soldering looks to be original (I have had some experience of soldering for what is now approaching 40 years).

Thanks to everyone who contributed to my other posting regarding "AR-9 basic re-capping advice". This is on-going and I will be most happy to update as things progress. This site has been of great interest to me and of great benefit, I have harboured the desire to repay the use of the facility in some way, should the opportunity arise. The following may be obvious to many, but if it helps anyone I shall be gratified. On to the subject matter. I have relatively recently been fortunate enough I feel to come into the possession af a pair of AR-9 speakers, I believe possibly a relatively rare thing here in the U.K. They were in a great basic condition, but as is the nature of these things, new broom sweeping clean as they say, I have been "going through them" thoroughly checking their integrity. obviously the matter of replacing the capacitors was/is being dealt with in my other posting. I had when listening to music, at times, (higher volumes, certain frequencies/instruments) thought I noticed some distortion in perhaps one of the lower midrange drivers, upon removal and inspection I discovered the following as illustrated in the first picture (don't worry, it's a very blunt knife !). The dustcap had partially parted company with the cone. Source of the distortion problem discovered and rectified by re-glueing the offending dust cap. However, and this is what may be of more general interest and perhaps help to others, is that upon further inspection the apparent cause of the dustcap detachment was discovered. The flexible wire lead from the positive connector to the voice coil, when the cone was at rest, appeared to be too short with almost no surplus wire to allow movement of the cone. It seems this was done at the time of manufacture. I did compare with the other speakers LMR driver, and it was only this one wire which was apparently too short. In practice, with the travel of the cone when playing, no doubt at higher volume levels, the wire was being pulled taught which resulted in the pulling away of the cone from the dustcap in precisely the location where the wire passes through the cone to the voice coil. Of further interest I believe, this in effect "strangled" the driver from reproducing sound as it should. Thinking about this further, it would never be possible to quickly check for the possibility of a short wire by pressing the cone inwards, it would only be when the cone moves outwards when being driven that the wire/wires could possibly be put under tension either partly or fully. I have rectified the situation by slightly swiveling and gently bending the input tabs on the driver, as in the second picture, to equalise the length of wire from both the positive and negative connectors to the cone, thereby leaving an equal amount of "slack" to allow full movement. I am now pleased to report that there is no distortion, and that whilst I appreciate there is some psychology attached to these matters, the sound seems to be somewhat improved. I do hope the above may be useful to others to bear in mind. P.S. Whilst there is a picture posted, if anyone might notice, does the foam on the driver look to be original/the correct profile ? also what are the correct dimensions of the driver foams for the AR-9 ? For example what is the correct woofer roll profile/size ? What is the correct profile/size for the lower midrange ? Thanks, Lance.

Thanks for all the help and suggestions from everyone. All done (both speakers) with Mundorf E-Cap plain (other than the 2500uF and 470uF on the woofer circuit). Unfortunately I am not sure I like what I am now hearing. I have tested all the original sub 20uF Elcap cap's which were removed, of note the 80uF were of PYE (AR9EK, UK assembled speakers?) manufacture, (my multimeter cap testing facility only goes up to 20uF) and they all seem to be within tolerance. I think I preferred the original sound before I changed out (nearly) all the cap's. The choice of Mundorf was to try to keep to as close to the original specification as possible. The change was thought potentially wise due to the age of the original cap's. The speakers were, when they came to me, apparently in somewhat remarkable condition for their age, I think week 34 1980 is marked on at least one woofer, and the crossovers were original with no physical signs of leaky cap's. Observations please most expert chaps ! (In error I have duplicated this post on DavidR's post regarding his own re-capping experience, hope no confusion ensues !)

(Following further posted, as should have been originally, in "AR 9.Basic re-capping advice"). Thanks for all the help and suggestions from everyone. All done (both speakers) with Mundorf E-Cap plain (other than the 2500uF and 470uF on the woofer circuit). Unfortunately I am not sure I like what I am now hearing. I have tested all the original sub 20uF Elcap cap's which were removed, of note the 80uF were of PYE (AR9EK, UK assembled speakers?) manufacture, (my multimeter cap testing facility only goes up to 20uF) and they all seem to be within tolerance. I think I preferred the original sound before I changed out (nearly) all the cap's. The choice of Mundorf was to try to keep to as close to the original specification as possible. The change was thought potentially wise due to the age of the original cap's. The speakers were, when they came to me, apparently in somewhat remarkable condition for their age, I think week 34 1980 is marked on at least one woofer, and the crossovers were original with no physical signs of leaky cap's. Observations please most expert chaps !

Sorry ignore below (edited), it's getting late here in the U.K. Its the 4 and 24 I should be looking at ! I looked back at the pictures that I took when I first opened up the speakers. A poor picture but when zoomed in the 80uF is definitely rated at 100v. Red one, bottom right.

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 !

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.

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 !

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.

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.

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.

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.

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.