DavidR

Yes, the 6680 mobile communications grade. Attached is a picture of them.

Caution with some of those old oils. They could be askarel or a form of it. Askarel is a PCB oil.

This model does not show up on Apheno's list which goes up to 1998 with the AR303A. This may be the reason for no posts. Most of us are not familiar with this model. Here is the history of AR: In 1967, Acoustic Research was bought by Teledyne, Inc., and for the next 22 years it continued development and operations in Cambridge as Teledyne Acoustic Research. Technological breakthroughs during this period included the high-current amplifier. When purchased by Teledyne, AR was the world's second largest supplier of branded loudspeakers. Although Acoustic Research continued product development, by 1989 AR had dropped to fifth place worldwide, and Teledyne sold the company to their major competitor, Jensen Electronics. In 1998, Jensen, including AR, was sold to Recoton Audio Corporation. Under both Jensen and Recoton, the AR brand continued development in the speaker industry, including the environmental controls that allowed a speaker to be placed in different room areas, the Acoustic Blanket that minimized diffraction and interference in speaker baffles, and a speaker line designed to complement home theater and the digital technologies of the 1990s. In 2003, Audiovox (now Voxx International) acquired the U.S. audio operations of Recoton, and continues with AR-brand speaker development and sales. An associated firm, AB Tech Services, provided maintenance of AR speakers until mid 2014. Web-based audiophile communities lamented the closure of the company and apparent liquidation of stock. As of July 2014 CM Tech Support assumed responsibility for Acoustic Research parts and service. So these were probably made after 1998 by Recoton. Hopefully someone will come along who has some knowledge on them.

Do you know what type of glue they used?

Hook up the other woofer in the cabinet that had the issue and see if it has problems in that cabinet, too. If it does it could be a wiring and/or soldering issue. Doubtful it is a capacitor issue but maybe.

Some one at the Carversite might have info. https://thecarversite.com/

cabinet air leak perhaps Is there a good seal on the driver gaskets ? Are the gaskets in good condition ?

I'm wondering if he's happy having (what looks like) used NPE (except for the 4uF). I beginning to think this might be best for the old ARs to sound like they were intended to. I used NPE in my 90s and 10Pi rebuilds with a small poly cap in parallel on the series caps and am very happy with those results.

Beautiful work Larry. Neat and tidy.

TUBES FOR SALE - All tubes have been tested on my restored Sencore TC142 for shorts, grid leakage and emissions. > Tung-Sol 5AR4 Rectifier, used – tests new. 113/113 emissions. $25 > Genelex GZ34 Rectifier, New/never used. Was my back-up. $40 > (2) Tung-Sol 12BH7A, shiny black plates, halo getter, date code Dec. 1960, test 107/107 and 106/106, Original boxes. $45 each > GE JG-5751 military issue (12AX7A/ECC83) with triple mica, grey plate, O-getter, tests 96/97. $35 > Telefunken 12AX7, diamond on bottom, logos worn off, gold pins. Used but tests NOS 105/105, repro box. $105 > Webcor by Mullard 12AX7 I61 BOH (rare), repro box. Used but tests NOS 106/104. $80 > (2) RCA 6680/12AU7A communications grade. Dark grey plates, halo getter. Original boxes in fair minus condition. Measure 98/98 and 98/98. $30 for the pair. > Mullard CV4003/M8136 (12AU7 alt). British military issue, original box. Used but tests NOS: 96/96; $90 >> Contact me (via PM) if you want shipping cost and/or pictures of a particular tube. PLEASE DON'T WASTE MY TIME WITH RIDICULOUS LOW BALL OFFERS

Craig's List works and there is no seller's fees.

Dave Shirly at DHS Speaker in Feeding Hills/Agawam, MA. He does a lot of Bose work. http://www.dhsspeakerservice.com/

Dayton is a low end film cap. Time might help sound better. Do not be afraid to use NPElectrolytics. I believe F&T and Mundorf Ecaps (made by F&T) make caps in Germany . They are a well made NPE. Should you want a bit more detailed high end then add a quality 0.01uF film bypass on each series cap by paralleling them. I did this on my AR90 and 10Pi and I'm very happy with the sound. Old NPE caps start acting more like a resistor than a capacitor.

Crossover caps need to be non-polar as the current has to be able to pass in both directions. The reason for the (+) is it probably indicates the inner foil and should connect to the destination (driver). All of the 2500uF caps in my 9s and 10pi have the (+) and they are all connected to the driver/red wire marked + on the driver.

Only when listening to jazz.

I never baby my ARs

I went that route also; except I added a small film bypass cap to the 2 series caps.

Gorgeous examples of the 10Pi !

Translation: Unfortunately it is true, they are all dangerous solvents, to be used with caution, with protective clothing or outdoors. I worked in a coatings and printing facility and was the manager of 2 solvent recovery systems and a distillation system. Was also 'rewarded' with a dual role of EHS Manager. The problem with toluene is that they keep lowering the threshold limit value, over and over. So what was OK when I was working with it is now a dangerous environment.

ALL nasty solvents. Wear nitrile gloves at the minimum and a respirator with carbon cartridges and/or work outside. Beware that acetone has a flash point of 0'F. I believe Nitrol thinner is a mix of xylene and methyl benzene. Toluene will pull fat out of your system right thru the skin and attacks all organs.

Roy, I did find it odd that the 032 tweeter and AR91 and 92 don't appear on that 1986 parts list. At least I was unable to find it.

I took a look at the1986 parts list in the library here and couldn't find anywhere it mentioning replacements. I do have this on my hard drive: Logic would say its the other way and I believe your previous post(s) state this as well. Also Carl measured the resonance and the 028 has 1/2 the resonance of the 032. The 028 won't play low enough for the AR91 and 92 and the 032 could burn out the vc if used in an AR9 or 90 when played hard.

Stimpy, doesn't the 032 only have ferrofluid on one side of the VC ? I want to know how they keep it on one side ........

At some point we may will be forced to accept a swap or one of the replacements I linked above. It's inevitable.

I believe it was RoyC who broached this subject and tried an 032 in an AR9 and could hear no difference.