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lance G

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Posts posted by lance G

  1. Ar9, modulus and impedance argument before and after recap

    in Acoustic Research

    Posted

    Many thanks to you Giovanni,

    Attached picture is of one of my original crossovers before recapping all EXCEPT for the 2500 uF. Apparently mine are Callins as yours were, so seems like it's time to change them out !

    Your information is really useful to me as I was given the impression, including from the forum, that it was acceptable to leave the 2500uF cap's in place as they are considered to be "historically robust".

    image.jpeg

  9. AR90s with rubber surrounds

    in Acoustic Research

    Posted

    1 hour ago, blanddawg625 said:

    I recently bought a pair of AR90s and found that all the woofers- 2 8" and all 4 10" have been resurrounded with rubber instead of foam. I have read that it is not so bad for the 8", but what about the 4 10" woofers? How will this effect the sound and is there a remedy for this. I have already noticed a lack of efficiency with them but what else will be different. Thoughts?

    Maybe some new capacitors in the crossovers might be needed ?

  13. AR-6 RE-cap ....increase in volume????

    in Acoustic Research

    Posted

    I must bow to RoyC's superior knowledge but my personal thoughts are: For the speakers to make any sound a signal of some level has to be reaching them. If they were disconnected altogether there obviously would be no sound.

    They are passive devices, I would be be looking elsewhere. Perhaps the capacitor change has made the speakers more sensitive and you can now hear a signal that was always there ?

    I guess some form of RF or induction could be responsible ? How far away are your electronics from the speakers ?

     

  14. AR90 restore project

    in Acoustic Research

    Posted

    3 hours ago, Mr. Weather said:

    The restored finish looks good.  I'm pretty well versed on refinishing wood but this is a delicate project so I've been doing some reading.  I see you used Watco Danish Oil which is a popular choice and I would not rule that out.  I ran across something called Odie's Oil which is billed as a solvent-free oil and wax that seems to give good results for many people.  So I picked up a can of that to exerpiment with.  I have no walnut wood to experiement on but I can scrape up some birch and oak and see how it performs.  However, I think big hurdle is how to mask the front and rear of the cabinets to avoid getting paint stripper on the factory black finish.  Sanding as mentioned, could be an alternative, and that would give me much better control of paint removal.

     

    Below taken form the AR9 manual, I suspect it's the same for the AR90.

    http://www.classicspeakerpages.net/_Media/ar9_or_manual_page32-2.jpeg

  15. AR90 restore project

    in Acoustic Research

    Posted

    I personally would be inclined to leave the high range and upper midrange drivers in place during any restoration. The inset foams surrounding the drivers are rare and unobtainable now, I would expect the foam to crumble if any attempt were made to remove it in an effort to reach the driver securing screws underneath. It's nice to see a set still on a pair of speakers, most seem to have disappeared now.

    Put some sort of protection over the drivers, perhaps some sturdy card or thin plywood whilst restoring the rest, cabinets etc.

    I don't think there would be much to gain by removing these upper drivers anyway, crossover (which is situated in the base behind woofers) callins capacitor replacement is more relevant to any refurbishment/rebuild.

    I have AR9's now, but had a pair of 90's previously. I loved them, and they are physically easier to live with than the larger 9's.

    You have the makings, after sympathetic restoration of the cabinets, grille cloth and badges, and (likely) crossover capacitors, of some superb speakers.

    I would go on to say enjoy, but it sounds like you already are !

    Footnotes; Check out images on the internet for confirmation of the original black painted cabinet areas. Quite simply it's the backs and the areas usually covered by the grilles. AR9's are fully veneered other than the backs which are black. Of note the upper midrange drivers are unique to the AR90 and AR9's, another good reason to leave them alone, fortunate that these have not been pushed in unlike the lower midranges. Pulling out with tape should hopefully sort those and at the end of the day they are only dustcaps which could be relatively easily replaced. Finally, your cat is apparently an exhibitionist !

  17. AR 90 first time listen and amplifier pairing question

    in Acoustic Research

    Posted

    I think the following applies to your amplifier ? It may be of some relevance to your perceived issue ?

    IMPEDANCE SELECTOR switch
    Do not change the IMPEDANCE SELECTOR switch
    while the power of this unit is turned on, as doing so may
    damage the unit.
    If the unit fails to turn on, the IMPEDANCE SELECTOR
    switch may not be fully slid to either position. If this is the
    case, remove the power cable and slide the switch all the
    way to either position.
    Select the switch position (LOW or HIGH) according to
    the impedance of the speakers in your system.
    Rear panel

    CAUTION
    Switch
    position Impedance level
    HIGH
    • If you use one set (A or B), the impedance of
    each speaker must be 6 Ω or higher.
    • If you use two sets (A and B) simultaneously,
    the impedance of each speaker must be 12 Ω
    or higher.
    • If you make bi-wire connections, the
    impedance of each speaker must be 6 Ω or
    higher. See page 6 for details.
    LOW
    • If you use one set (A or B), the impedance of
    each speaker must be 4 Ω or higher.
    • If you use two sets (A and B) simultaneously,
    the impedance of each speaker must be 8 Ω or
    higher.
    • If you make bi-wire connections, the
    impedance of each speaker must be 4 Ω or
    higher. See page 6 for details

  19. AR 90 UMR Collapsed dome. Can it be fixed?

    in Acoustic Research

    Posted

    34 minutes ago, uarnutz said:

    Eureka. It worked! Here's rev 1 using a professional riggers tape. You know, the kind that sound and lighting engineers use for laying their cables. That was after trying generic duct tape and packaging tape. It's not 100% but, I may still try to find an even stickier tape. What do you think? Thanks for the tip.

    AR90UMRv2.jpg

    Well done ! That should be enough, quit while you're ahead.

    My driver was far, far worse that yours. I think mine was likely subjected to freezing temperatures and pressurisation in the aeroplane cargo hold which totally reversed/collapsed the complete dome.

    Report back when the rest of the work is done with an update, and enjoy !

  20. AR 90 UMR Collapsed dome. Can it be fixed?

    in Acoustic Research

    Posted

     

    3 minutes ago, uarnutz said:

    Thanks. Yes, it definitely looks as if it is actually being sucked in under vacuum. I suppose that means the seals are good anyway. Are these drivers the ones that are mounted in a tube? Maybe I should loosen the mounting screws and then apply suction.

    This will not make any difference. You could remove the driver altogether and it wouldn't help, other than you will likely be able to confirm that it's a (to my mind, in my experience an apparently?) sealed unit. From what I can see in your picture I would personally try using the tape method for starters, but you will need a tape that is strong enough to stay adhered while you gently start pulling, but of course can then be readily removed when you have hopefully succeeded. Perhaps first gently heat the cone with a hair dryer (?) and keep a gentle sustained pull on the tape to allow time for any air to (hopefully via somewhere!) find its way back into the space behind the cone, thereby re-balancing the internal with the external air pressure.

    Not something I would ultimately be keen to try, but perhaps a worst case MIGHT be to gently insert a small needle tip just through the centre of the indentation to both allow some air into the driver and to tease out the dent. A tiny drop of clear sealer of some type could be used to seal the hole. Again I would try this on a previously warmed cone.

    DISCLAIMER ! All the previous is based on my own experience and opinions. Please don't blame me if when (perhaps foolishly😀) following my suggestions you bugger it up ! Perhaps wait a little longer for other members, who very likely know far more than I, further input while you crack on and replace the perished woofer and lower midrange foams ?👍 And as the sage Stimpy very wisely suggested change the (if relevant) Callins capacitors.

  21. AR 90 UMR Collapsed dome. Can it be fixed?

    in Acoustic Research

    Posted

    12 hours ago, uarnutz said:

    Thanks everyone. I could not get it to work using the dampening and suction (by mouth, using a cardboard tube.) I can see the crease pulled out but, it immediately collapses back. It seems to have some sort of memory. How wet does it need to be? I actually let a wet piece of paper towel rest on it for a minute or two.

    I have had the same issue with a used (identical) driver imported from the USA into the UK for my AR9's. I think the pressurisation/temperature change during the flight likely caused what amounted to the total collapse/inversion of the cone.

    I don't personally think that wetting will make much difference, the cones seem to be coated (sealed?) with a type of tacky/sticky resin (therefore airtight?)

    I do wonder if the units are sealed ? or at least pretty much airtight, it appears that there is a battle against an internal vacuum when in my efforts to pull the cone out, as you also seem to have experienced, just saw the cone being apparently sucked back in. I ultimately had some reasonable/moderate sucess by gently heating, the use of tape and the gentle, dexterous use of a vacuum cleaner. In the end not a perfect result visually, but at least it resulted in an apparently serviceable driver.

    I suspect very gentle efforts, trying to allow some time for air to gently "flow" back inside the driver is the way to go, "little and often" or "softly, softly catchee Monkey" would seem to be the order of the day !

    I believe the driver is a 200028-0? Used only in the AR9 and AR90 models. Getting hard to find good working replacements now, so do take your time and exercise caution.

    I had AR90's in the past and loved them, I eventually got my bucket list AR9's here in the UK. IMHO any careful effort you put into your speakers will likely be richly rewarded, they are cracking speakers, easier to live with than the AR9 (physically), and right up there sound wise.

    Good Luck !

    And do please update us on your efforts.

     

  22. AR9 speakers and Quad 606 amplification ?

    in Acoustic Research

    Posted

    34 minutes ago, DavidR said:

    My AR9 Owner's manual has the impedance dip to 3.2 ohms.

    I have no clue about your Quad 606. Sorry.

    I used to have a CT-7. Nice, attractive Pre. Doesn't the CT-7 have 2 Pre Outs? or am I thinking of my C-1 ?

    Hi David, thanks for the quick reply, and don't apologise regarding the 606, it is after all a U.K. amplifier.

    Your interesting observation from the AR9 manual regarding an impedance dip to 3.2 ohms is interesting. I did today find an old Quad 606 amplifier review (http://www.meridian-audio.info/public/606[2223].pdf) which states to quote; "it should be able to drive any loudspeaker except those dipping below 3 ohms", so hopefully, if correct, this should be re-assuring.

    However I wonder what the seperate minimum impedances might be for each seperate AR9 circuit when bi-amping ? With one 606 amplifier driving the lower midrange, upper midrange and tweeters, and a seperate 606 amplifier for the bass drivers ?

    On brief inspection my CT-Seven has only one pre-out, but although not ideal, I do have a cable splitter to enable me to send a signal to each 606 amplifier for bi-amping.

  23. AR9 speakers and Quad 606 amplification ?

    in Acoustic Research

    Posted

    I appreciate this is a mainly U.S. biased forum, but I do have a question from the other side of the pond in the U.K.

    Anyone have opinions on driving the AR9 with U.K. manufactured Quad 606 amplification ? I perceive that the AR9 thrives on plenty of power ?

    I am currently using a single Quad 606 and have another 606 which I have dabbled in, and can dabble again with bi-amplification. Again I perceive that the AR9 can "dip" to around the 2 ohm load area but have found it difficult to confirm the suitability of the Quad/s in this regard.

    I use a Carver CT-Seven pre-amplifier as I like the convenience of the remote control volume and switching. I have, and have tried a Carver PM 1200 amplifier, but I found it hard to live with the cooling fan noise and I have tried to avoid any fan modification (silencing) to date.

    Any (polite) suggestions or opinions from the more technically minded greatly appreciated !

  24. AR9 Recap or not?

    in Acoustic Research

    Posted

    Hi Frank,

    Sorry to hear you're not in the UK. I was initially intrigued because I am not sure how many AR9's made it or were assembled over here.

    Regarding the Mundorf NPE's and my earlier posting which it appears you have seen ? To be honest at that time I didn't know what I should expect.

    The cap's in my speakers when I inspected them were obviously original, and the speakers sounded good, to me, when I first got them used from here in the UK.

    I changed the cap's, I think it was two years ago, very largely on the basis that they were obviously pretty old and likely past their best, and I guess I expected to hear a, potentially radical, change/improvement once the new cap's were fitted. With this in mind I perhaps felt a little disappointed when this apparently wasn't the case.

    However I do now have peace of mind that the cap's are good for some time to come, and are both in specification and of the type originally fitted. I did test the Mundorf's before fitting, and also tested the old cap's when they came out. I do recall that some of the old cap's had drifted but not to an obscene degree. I am also now more at ease that potential danger of damage to the very hard to find/replace here in the UK drivers, has hopefully been minimised.

    Regarding the subjectivity of any listening outcome, I feel sure you will be aware there are a lot of variables. Not least personally to me is my increasing age and no doubt as a result the reduction in my hearing of the higher frequencies.

    In closing, HI FI collective were nothing but professional in my dealings with them, and I think it unlikely that you will have made a mistake by using the Mundorf's. I see people dabble with other capacitor types, but I considered that the original amount of research and development warranted the use of OE specification capacitors to retain a sound as near as possible to the original, sound that was so highly regarded at the time the speakers were released.  I hope the above helps, both yourself and shacky.

    Lance.

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