Posted by Russellc [ 66.142.53.230 ] on September 25, 2004 at 09:57:00:
In Reply to: Opinions needed: Aluminum or Pascalite? posted by Floyd Andrews on September 24, 2004 at 17:54:46:
Unless you have availability to NOS, I don't belteve pascalite is still available. I have the 908 with symbiotic and they don't sound as awful as people say. That said, the straight aluminum is the one to go with for home use but it is no longer available either. For PA the pascalite or symbiotic. (if you can find them) Greatplaines audio is the place I have had the best luck with. Bill worked for altec and has most of the manufacturing equip from the day. Others make replacements also, but I have not tried them. Another feature of many drivers with symbiotic diaphrams that can be improved on( for home use) is under the covers. Remove them VERY carefully and look. If you only see shiney metal dome and there is a thick felt pad in the back of the cover, just replace the diaphram and close it up. If you see a plastic looking dome and there is no felt in there, I would suggest the following.( again, for home hifi use) When you order your diaphams from bill, tell him you want the parts to remove the loading caps as well. The loading cap IS NOT a capacitor, it is that plastic thing covering the dome. The parts should be: 2 felts to line the back of your covers, and six short screws. When you remove the old diapram and the plastic thing, do not reinstall the plastic thing. the new short screws will make up the space equal to the thickness of the plastic thing you are leaving out.
These plastic loading caps were used in an effort to make heavy use drivers live longer. These same use drivers were usually equiped with the symbioticdiaprams as well. Both measures increased heavy use reliability, but hampered high frequency transients and extension.
If your use is home stereo try this advice. However, if PA is your use, I would call Bill @ Greatplaines audio and ask. With the loading caps removed and the "regular" aluminum diaprams in stalled, they will be basically a 902- A sonically. Hope this helps. If any is unclear, Bill can explain it better than I.
Russellc
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