Kuja Posted September 10, 2005 Report Share Posted September 10, 2005 Hi,I have some more questions regarding AR 12" drivers from my previous post:http://www.classicspeakerpages.net/dc/dcbo...g_id=7040&page=The drivers were badly refoamed so I had to refoam them again.The guy that did the new job for me, was official AR repairman for more than 20 years.He said that the previous repairman, prior to refoaming, for some reason removed some ring that should sit between the steel frame and the foam surround.Did all versions of 12" drivers had this ring and what is the purpose of it? He added it again and this is how it looks now:http://www.kujucev.com/ar/ar12inch_c.jpgHe also said that the dust cap must be porous and he did put a new one which is made of some sort of textile and now I can easily see the magnet through it.Again, did all versions of 12" drivers had porous dust caps and why?New dust cap:http://www.kujucev.com/ar/ar12inch_d.jpgThanks in advance,Aleksandar Link to comment Share on other sites More sharing options...
Kuja Posted September 26, 2005 Author Report Share Posted September 26, 2005 No answers.... anybody has any idea?The 12" woofers in question, come from a pair of AR98LS.Do all AR 12" woofers have masonite rings and why do (did) they have it?Also, do all 12" woofers have porous dustcaps and why do (did) they have it?What would be the effect (bad?) if I have those two things added on a driver that maybe didn't have it originally, since it is a newer production unit?I know that AR98LS are not considered as "classic" ARs on this forum, but after the restoration I performed on them, they sound just great!Restoration details:http://www.kujucev.com/ar98ls/ar98.htmThis is the only place on the Internet, that I can get this answered...Thanks,Aleksandar Link to comment Share on other sites More sharing options...
tysontom Posted September 26, 2005 Report Share Posted September 26, 2005 >>Do all AR 12" woofers have masonite rings and why do (did)>they have it?>Yes, the masonite ring lifts the surround to the proper height to make certain that the voice coil and spider remain in the center, "resting" position properly. Without the ring, the voice coil will rest below the center position, and will more easily "bottom" when driven hard. The woofer will not have its full excursion capability without the ring. The ring shown in your pictures that was installed on your repaired woofer is actually wrong, too, as it is too thin, but the differences are very slight.>>Also, do all 12" woofers have porous dustcaps and why do (did)>they have it?>I don't think the porous dust cap is mandatory, as the voice coil has vent holes all around the former below the coil itself. These vent holes allow air that is caught under the dust cap to escape; or a better way to look at it is that the vent holes allow the pressure to equalize. The porous dust cap does probably help somewhat, but is not necessary. Some of the later AR woofers did not, in fact, have porous dust caps, and those that appeared to be porous were treated with butyl-rubber compound. A porous dust cap does allow an air leak into the cabinet, but this tiny amount is neglible, and does not affect the performance of the woofer. You do not want the cabinet to be *hermetically* sealed, in any event, just *acoustically* sealed.>>I know that AR98LS are not considered as "classic" ARs on this>forum, but after the restoration I performed on them, they>sound just great!>The AR98Ls is an excellent speaker, and is definitely one of the AR "classics." It is, of course, less-famous than some of the old ARs, but it was held in high regard by reviewers and critics and has always been considered one of the best loudspeakers of its generation. In its original configuration, this speaker was capable of very flat and uniform anechoic on-axis response, and because of its excellent dispersion, it also had excellent integrated-power response. I can't think of a single contemporary high-end speaker made today that could surpass this series AR speaker in integrated-power response.--Tom Tyson Link to comment Share on other sites More sharing options...
Kuja Posted September 26, 2005 Author Report Share Posted September 26, 2005 Tom,Thanks a lot!!!I didn't know that AR98LS was regarded so highly.I hope that someday I will be able to find some old AR98LS reviews on the internet.Thanks again,AleksandarPS how thick this masonite ring should be? The repairman did the best job that he could do, since he made this ring by himself from the scratch... Link to comment Share on other sites More sharing options...
tysontom Posted September 27, 2005 Report Share Posted September 27, 2005 >Tom,>>Thanks a lot!!!>>I didn't know that AR98LS was regarded so highly.>>I hope that someday I will be able to find some old AR98LS>reviews on the internet.>>Thanks again,>>Aleksandar>>PS how thick this masonite ring should be? The repairman did>the best job that he could do, since he made this ring by>himself from the scratch...Measure the thickness of the ring: it should be 1/8-to-3/16th inches thick. A little variance can't make any difference, but remember that the total *linear* travel of the woofer cone is designed to be 12.5 mm or 1/2-inch, so the cone should be positioned properly in the gap.http://www.classicspeakerpages.net/dc/user_files/623.jpgAR-10Pi 200003-0 woofer, 1976 vintage. Note the dust cap: it is porous cloth material, but was treated with butyl-rubber compound, thus making it more-or-less air tight. I therefore don't think the porosity of the dust cap is crucial because of the vent holes in the voice-coil former. The masonite ring is 1/8-to-3/16th-inches in thickness. This woofer also has the correct 5/8-inch diameter half-roll surround, and the surround work was done without any shims.--Tom Tyson Link to comment Share on other sites More sharing options...
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