hpm speaker dope
- Thread starter Kevin68
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Jnevill
Super Tweeter
That's a pretty clean looking HPM woofer, what are you shooting for? Preventative maintenance? AFAIK these were doped up for life, but i have no idea what they might have used, i'd like to know myself. It couldn't hurt to touch 'em up here some 35 years later. I assume it is a non-petroleum based tar like substance, let me see what google says.
Jnevill
Super Tweeter
According to wikipedia they used a "greased cloth surround"...
"At the time, most speaker drivers were manufactured using paper cones and foam surrounds. Another revolutionary feature that the HPM-100 speakers had was carbon-fiber blended tweeters, mid-ranges, and woofers; all with greased cloth surrounds. Carbon fiber, a technology which has an unparalleled strength to weight ratio exceeding titanium and is used in the construction of military aircraft, is lighter, more rigid, and does not rot away over time like paper and foam do. The weight of the carbon fiber, combined with cloth surrounds, allows the drivers to move and vibrate more easily, replicating sound much clearer. Compared to the usual cheap, stamped steel baskets most speakers incorporated at the time, the three drivers also have solid aluminum die cast frames, intended to eliminate resonance and unwanted rattling and noise. These features have contributed to the endurance, reliability, and longevity of the drivers."
"At the time, most speaker drivers were manufactured using paper cones and foam surrounds. Another revolutionary feature that the HPM-100 speakers had was carbon-fiber blended tweeters, mid-ranges, and woofers; all with greased cloth surrounds. Carbon fiber, a technology which has an unparalleled strength to weight ratio exceeding titanium and is used in the construction of military aircraft, is lighter, more rigid, and does not rot away over time like paper and foam do. The weight of the carbon fiber, combined with cloth surrounds, allows the drivers to move and vibrate more easily, replicating sound much clearer. Compared to the usual cheap, stamped steel baskets most speakers incorporated at the time, the three drivers also have solid aluminum die cast frames, intended to eliminate resonance and unwanted rattling and noise. These features have contributed to the endurance, reliability, and longevity of the drivers."
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spkrdtr
spkrfixer
Read post #10 here....http://www.audiokarma.org/forums/showthread.php?t=549586
Note though, other posters warn agains doping foam surrounds with PVA due to risk of stiffening up the foam a bit which could reduce bass response somewhat. YMMV
