BEC Posted October 31, 2008 Share Posted October 31, 2008 I don't see these diaphagms blown like this pair very often, so thought I might get a picture of these and post it. The voice coil has separated on these. This is caused by an instantaneous high power excursion that separated the coil so quickly that the coil does not show any discoloration from heat. Bob Crites Quote Link to comment Share on other sites More sharing options...
WMcD Posted October 31, 2008 Share Posted October 31, 2008 Very interesting. Many thanks for objective evidence. Because the forum gets questions about what went wrong. You are the Quincy of voice coils. Or in the style of other M.E.'s you speak for the dead. Smile. I suppose this is like so many industrial accidents. The potential witnesses seldom come forward to say, something like: "Yeah, we were driving them near the limits and then there was a magnificent peak, and they died.." Rather, no one saw (heard) anything. Just soft jazz in the background. I'd described my post mortem of some woofers. They had obvious heating. But I wonder if there was some long term heating on these K-77 which softened the glue, then there was the mechnical breakdown. Naturally, I defer to your observations, Doctor. Smile Wm McD. Quote Link to comment Share on other sites More sharing options...
BEC Posted October 31, 2008 Author Share Posted October 31, 2008 I could also add one more little observation. These tweeter diaphragms were "protected" by a polyswitch. I just don't think a polyswitch is anywhere close to fast enough to protect a tweeter from a high power transient. I submit the above picture as evidence. This was not an old tired polyswitch either. These came from 60th Anniversary Khorns. Bob Quote Link to comment Share on other sites More sharing options...
djk Posted November 1, 2008 Share Posted November 1, 2008 A PolySwitch takes a long, long time to blow (4 seconds at 2.5A, 40 seconds at 1A, for the model Klipsch uses, see the data sheet fig.16). EV rated the newer T35 to handle 50W for 10ms, the RXEF050 will pass 50W for 4 seconds. http://www.circuitprotection.com/catalog/radialDS.pdf Those look to be the new pacific-rim clones, are they close enough to the EV to use EV parts? EV ones failed like that when they were using the clear UV cure adhesive. Quote Link to comment Share on other sites More sharing options...
BEC Posted November 1, 2008 Author Share Posted November 1, 2008 "Those look to be the new pacific-rim clones, are they close enough to the EV to use EV parts?" Yes, these are the ones made in the far east. I replaced them with new EV diaphragms with the Copper Beryllium leads. By the way, these K-77Fs were also the new style with the horn that flush mounts without using Z-brackets. Guess I should show a picture of those. Bob Quote Link to comment Share on other sites More sharing options...
johnyholiday Posted November 3, 2008 Share Posted November 3, 2008 [:|] Quote Link to comment Share on other sites More sharing options...
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