John Warren Posted April 17, 2015 Share Posted April 17, 2015 (edited) For folks that own OLAs, the attached shows one way to reworked the grilles to re-stretch new grille fabric. http://northreadingeng.com/Forum/index.php?topic=18.0 Edited April 18, 2015 by John Warren Quote Link to comment Share on other sites More sharing options...
Deang Posted April 17, 2015 Share Posted April 17, 2015 Awesome. Nice work John. My daughter has the four I reworked many years ago - the grills are the hardest part of the restoration process, and good call using electrolytics in the networks. Quote Link to comment Share on other sites More sharing options...
John Warren Posted April 18, 2015 Author Share Posted April 18, 2015 (edited) Thank you Sir! I replaced the electrolytic capacitors with films (Electrocubes) of the same capacitance magnitudes. Measurement wise, there's a small difference in the before and after plots but I wasn't that familiar with the sound before I started the project to say conclusively that the change was for the better. That said, they sound pretty good! I think the black, steel frame woofers were introduced at the end of the production campaign of the original prior to the introduction of the "New" Advent. They were then used until the New Advents became NLA. The system Q that I measured with the steel frame woofer is around 0.9-1.0 which seems high to me. My recollection was that the early production units with the Masonite ring were closer to 0.7 (maximally flat response). The original grilles really were not well designed. Edited April 18, 2015 by John Warren Quote Link to comment Share on other sites More sharing options...
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