owlsplace Posted July 22, 2016 Report Share Posted July 22, 2016 I did say I wasn't going to do anymore speakers this year, but ... AR-7 cabinets in mahogany? I've seen them in teak. This doesn't look like walnut to me. They are not vinyl which was the standard finish in the US. Any opinions? My only other dilemma is whether or not to leave the Sprague blue caps or replace. I'd prefer to change them though I'm not sure I have the correct foil caps on hand at the moment. Roger Link to comment Share on other sites More sharing options...
ra.ra Posted July 22, 2016 Report Share Posted July 22, 2016 Timely thread, Roger - - I just recently finished restoring two pairs of AR-7's. One pair has real wood (s/n 0058XX, see pic attached) and one pair has vinyl (s/n 206XX); both have U.S. paper labels and front-wired tweeters. With the caps, I fully expected to be replacing them, but when all four blue Sprague caps (6uF) were found to measure between 6.15 and 6.48uF, I decided to leave them all, and I think they sound terrific. As you already know, the two-position tweeter control switch seems to have only a subtle effect, but it is discernible. I assume from the thread title that your speakers have Euro labels, and I've only seen the teak veneer option on Euro versions (and only from reading via this forum). Two other common features I've often seen with Euro 7's are the brown spatter paint on the cabinet backside and rear-wired tweeters. Also, there was a version called AR-7x, Euro only, which I believe was the exact same speaker except that the tweeter contained ferrofluid. Your speakers look great and have more figure and coloration than mine do, but I don't think they are mahogany. I believe I may have read a statement from Tom T where he said that the real wood AR-7's were actually birch stained to look like walnut, which is sort of supported by this claim of "wood cabinet walnut finish" shown on this literature. I would never have guessed this formula upon personal inspection, but since I actually found this particular finish to be a little difficult to work on and unlike other walnut cabinets, I am inclined to believe that is what I have, and yours may be the same. Link to comment Share on other sites More sharing options...
owlsplace Posted July 23, 2016 Author Report Share Posted July 23, 2016 Birch doesn't have this grain pattern -- either mahogany or its northern hemisphere equivalent, walnut would be my guess. I helped install some 3/4" mahogany paneling years ago that looks very similar so that is why I suggested it as a choice. Another issue, both of the AR-7 sets at this location are wired opposite of the diagram in the archive below. I don't know if I should change these or just mark the terminals #1 as plus and #2 as minus -- woofer (+) red wire is connected to terminal #1. Kind of threw me off and I opened up both cabinets again to verify which was a pain since they are assembled using a sealant rather than foam tape. Well, will open again and replace the Sprague caps with film caps as they are reading between 7 and 7.4mfd on my equipment. Esr should drop as well as voltage loss although I doubt it will be enough to notice the difference but it is not a big expense to replace these. I didn't expect to spend so much time on these -- what is that saying? If you are on a schedule, don't go sailing ... Not sure where the 1-1/2" cone comes in as these are the standard 1-1/4" tweeter designed by RoyA IIRC. These cabs have Thorndike and High Street labels. Roger Link to comment Share on other sites More sharing options...
ra.ra Posted July 23, 2016 Report Share Posted July 23, 2016 Yeah, the birch reference threw me for a loop as well, but since yours have Euro labels, I don't know what else to say about the veneer species except that they look great. Re: 1-1/2" cone, some of the earlier AR literature (see above) identified it as such, while later brochures (see below) revised this to 1-1/4". Even the Hirsch-Houck review simply re-stated the early literature for this tweeter dimension and mentioned a "walnut enclosure" for the AR-7. You gotta love that side-by-side comparison with the AR-LST. Being the most simple crossover in the entire 'classic' series, the wiring should be very straightforward. The only thing to be mindful of is the opposite polarity of the drivers, which is consistently shown in all schematics. I suspect that the wiring is correctly connected, and that what you have yet to notice is that the positions of the "1" and "2" terminals in relation to the switch are reversed on the Euro version (see last pic here). Link to comment Share on other sites More sharing options...
owlsplace Posted July 23, 2016 Author Report Share Posted July 23, 2016 8 hours ago, ra.ra said: I suspect that the wiring is correctly connected, and that what you have yet to notice is that the positions of the "1" and "2" terminals in relation to the switch are reversed on the Euro version (see last pic here). Well, I noticed the Euro cabs have the crossovers installed upside down -- something to do with driving on the left side of the road? I have other projects going on and was somewhat annoyed that I couldn't finish these; however, I'm currently intrigued by what appears to be yet another anomaly from AR. AR-7 challenge: take a AA battery and a short piece of wire and connect the positive side of the battery to the #2 terminal and the negative side to terminal #1 while watching the woofer and tell me which direction the cone deflects -- in or out? Roger Link to comment Share on other sites More sharing options...
genek Posted July 24, 2016 Report Share Posted July 24, 2016 Looks like quarter-sawn teak to me. Link to comment Share on other sites More sharing options...
ra.ra Posted July 24, 2016 Report Share Posted July 24, 2016 This thread shows a gorgeous pair of Euro AR-7's in teak, and also includes Tom's statement about the U.S. wood version being clad in birch. And Roger, after looking at pics of AR-7 crossovers and comparing with the schematics, you've now gotten me very curious (and confused? ) about this polarity issue. In the attached composite pic, it appears the woofer positive (red) connects to the #1 terminal, which not only contradicts the three schematics we've posted but also the typical AR speaker where the #2 terminal is positive. This comment is made for U.S. version only, but apparently you've also got concerns about some Euro AR-7's you are evaluating. My speakers are not immediately accessible but maybe I can look closer to confirm later this week. Stumped for now.... Link to comment Share on other sites More sharing options...
owlsplace Posted July 25, 2016 Author Report Share Posted July 25, 2016 22 hours ago, genek said: Looks like quarter-sawn teak to me. Well the teak finish would jive with previously reported Euro cab veneers. These cabs have the dark brown backs rather than the splatter finish that TomT mentioned in ra.ra's reference post. The polarity thing probably wouldn't be a big deal back in the day but I tend to run multiple speakers so phase issues will cause cancellations, etc. Busy currently on other projects so play time is limited ... Roger Link to comment Share on other sites More sharing options...
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