iso Posted February 23, 2016 Report Share Posted February 23, 2016 I bought nice AR-7 pair from my trusted vintage shop. This pair seems to be fairly original with refoamed woofers. Teak veneer was in quite good condition. I did clean it a bit with mix of pine turpentine and BLO, but overal appearance did not improve too much as it was so good in the first place. Serial numbers are 31302 & 31303, wich is hardly surprising as this was supposed to be the first AR model to be sold as pairs in one cartrton. The woofers seems to be in useable condition, but I suppose that there has been some time since refoam as the foams have turned to look old and are close to black coloured. From pics you can see that the woofers do have some differences, even overal appearance does suggest that they may be the original ones. First... the cone material has aged differently... one cone is close to black on the other one is quite grayish. One frame do have black paint and the other one do have speckled black paint. Speckled paint is not due detoriation of paint, it looks that it has been such since day one. You can find the biggest difference behind cone. There is something that looks like glue or dope... that has been applied around neck of cone. Does anyone here know the purpose of this "dope" behind cone? #2 woofer does have clear 661 7544 production code but production code is not too clear on #1 woofer... but it may be 661 7539 or something like that. Production code of 6uF Sprague cap is 7417L. Unfortunatelly the other Sprague cap has been replaced propably when the refoam was made. Kimmo Link to comment Share on other sites More sharing options...
owlsplace Posted February 23, 2016 Report Share Posted February 23, 2016 Kimmo, Love that teak finish. My woofers are similar in color although I don't remember black paint on the baskets. The tweeters are front wired on this set and the sound board is not painted black -- serial numbers in the 16600+ range I have a Sprague 7421L cap you are welcome to if you want it. Here is an image of the cap: Roger Link to comment Share on other sites More sharing options...
ra.ra Posted February 23, 2016 Report Share Posted February 23, 2016 Those are gorgeous - - I doubt you'll ever find a better-looking pair of AR-7's than what you've got - - even the grille looks brand new. It appears your woofers were assembled five weeks apart in 1975, and slight differences in color of paper cone is nothing to worry about. It could be as simple as one of them suffered from a bit of sun exposure, or maybe they just represent different batches of cone material. The blobs on the backside of the cone appear to be hot melt glue which was probably used to secure the cap inside the cabinet - - not sure how it ended up there, though. The speckled woofer basket appears to be a build-up of residue resulting from some undesirable chemical action - - this is not uncommon. Try wiping it off with a paper towel and simple white kitchen vinegar. Great find, beautiful speakers. Link to comment Share on other sites More sharing options...
iso Posted February 23, 2016 Author Report Share Posted February 23, 2016 My trusted vintage shop described item to be " in very good condition, with little in the way of marks" and this is true. It is truly nice to have vintage audio merchant who has sensible pricing and who can describe items to be sale as honestly as he does. Cabs are truly good... I can imagine that only NOS ones may be better. Roger... this never came to my mind... but if you can put 6uF Sprague cap in padded envelope and send it to me in regular mail, send me PM... I will paypall postage to you. I actually replaced the caps, but I will replace them again if I can get pair for my Sprague cap. I will add pic about replaced cap and only defect in the cab that must be rectified. Acrylic putty has been used to seal woofers... and when I removed them one woofer loosened well, but other one pulled some particles of particleboard off, such a way that sealing the cab with regular gasket will not do. So... my plan is to mix PVA glue with wood dust and some small particles of wood and use it as filler. Maybe I can use woofer frame as die, after wraping plastic film around flange of the woofer. ra.ra. grille looks in the pic a bit better than it actually is, but simple cleaning will do when weather turns warmer here within 2-3 months. The blobs on the backside of the cone are propably hot melt glue as you suggested, but I do not think that they were applied here by accident. Bead of glue runs around cone from one coil lead out wire to other. Bead may have been here since day one... or maybe glue has been applied later during recone. Maybe fs was measured after recone and speckled woofer was found to have too high fs compared to black woofer, and glue was used to make fs lower, or something like that. Maybe someone here can verify if AR has used this kind of mod or not. It is possible that this bead of "glue" is one reason for harsh sounding midrange of this pair. I used to have pair of AR-7´s in the late 70´s and as far as I remember mids were not forward sounding... too distant would be far better way to describe AR-7 mids, if I remember correctly. Kimmo Link to comment Share on other sites More sharing options...
ra.ra Posted February 23, 2016 Report Share Posted February 23, 2016 Looks like you've got one of those Mullard "tropical fish" caps plus a second one in parallel. Never seen that in an AR, but they did show up in other models as mentioned toward the end of this thread. Link to comment Share on other sites More sharing options...
iso Posted February 23, 2016 Author Report Share Posted February 23, 2016 Yes... I removed this 2,2uF "tropical fish" from my EAR509 amplifiers, as input cap was not needed with my cap coupled preamps. I used it here as I had to make 6uF cap paralleling 3,9 and 2,2 cap... Kimmo Link to comment Share on other sites More sharing options...
owlsplace Posted February 23, 2016 Report Share Posted February 23, 2016 3 hours ago, iso said: ...Roger... this never came to my mind... but if you can put 6uF Sprague cap in padded envelope and send it to me in regular mail, send me PM... I will paypall postage to you. ... No problem, I'll just snip it off the crossover it is on and send it to you. Check your mail. Roger Link to comment Share on other sites More sharing options...
JeffS Posted February 24, 2016 Report Share Posted February 24, 2016 What a great and rare find. Real beauties! You could also go old-style AR and use Mortite to seal your woofers. Link to comment Share on other sites More sharing options...
iso Posted February 24, 2016 Author Report Share Posted February 24, 2016 Many thanks to you Roger... I just sent my contact information. One thing that I did not remember... AR-7 badge is placed in the woofer end of the grille, so in the first picture AR-7 with grille is upside down... Kimmo Link to comment Share on other sites More sharing options...
iso Posted February 25, 2016 Author Report Share Posted February 25, 2016 Roger has now sent one 6uF Sprague cap to me, so this is going to be propably the first recap where upgraded film caps are going to be replaced with original ones? Thank you Roger. There has been no other than ra.ra.´s suggestion about hot glue doping on back side of woofer... so it looks that it is "unauthorized mod", most likely done during refoam. I have now given the cabs cleaning with BLO, turpentine and steel wool, two coats of BLO with 2 intermediate sandings with 400 grit paper and water. They look now a bit nicer than in the pics abowe, where they were presented as received. Difference is not too big, but surface is now smoother. My next question is about tweeters. They are of back wired variety and magnet dia is about 54 mm. Are the tweeters original ones as there are at least two different tweeters for AR-7, AR-7x, AR-6, AR-MST in service part catalogues? Different magnet weights are specified, but it is hard to measure weight without breaking the tweeter... but as far as I remember, original AR-7 tweeter did use conventional VC and AR-7x used ferrofluid cooled VC. This was used as replacemet when my AR-7 tweeters failed back in 1977. Kimmo Link to comment Share on other sites More sharing options...
owlsplace Posted February 25, 2016 Report Share Posted February 25, 2016 Hey, you're welcome. This looks like the same tweeter in the orphan 4xa here. The vc lead in wire acts like a fuse when they are overloaded. I had to solder a bridge across the break to restore operation. Roger Link to comment Share on other sites More sharing options...
ra.ra Posted February 25, 2016 Report Share Posted February 25, 2016 Your tweeters are original and you are correct about the differences between the AR-7 and 7x --- see the attached thread for more specifics. There were several iterations of this 32 mm cone tweeter, and from what I've seen, the magnets are either 54mm (2-1/8") diameter or they are 60 mm (2-3/8"). Link to comment Share on other sites More sharing options...
RobHolt Posted February 27, 2016 Report Share Posted February 27, 2016 Black baskets are original factory. My AR7s have them and were definitely in untouched condition when I bought them. Link to comment Share on other sites More sharing options...
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