This is a common phenomenon that affects dome tweeters more so than cone or planar designs.
The voice coil lead out wires are subject to maximum stress along the length of wire that straddles the dome surround. It is round this point that it is most likely to burn out when being driven hard.
I have encountered quite a few blown tweeters that could seemingly be brought back to life just by applying light pressure at a point along the outside diameter of the dome. The pressure will often causes the wire to temporarily remake contact. This form of resuscitation does not make for an enjoyable listening session though.
Depending upon the particular tweeter design, it is often possible to remove the mounting plate/dome and 'unwind' a length of voice coil wire and reattach it to the appropriate terminal (taking care to route/secure it in the same fashion as the original run). It is sometimes obvious to the naked eye where the short is as one can usually see a dark spot on the wire and in some cases even 'feel' the break with a fingernail.
I have successfully repaired a number of irreplaceable (or overpriced) tweeters using this method. A fine tipped soldering iron and thin (ie. quick melt) solder work best. The lead wires are often secured to the rear face of the mounting plate with no more than a bit of sticky tape.
With very few exceptions (ferrous fluid loss), the change in sensitivity/performance has never been discernable. My sister’s old ‘70’s AR clones ran for 15 years on a ‘rewired’ tweeter until the inevitable bass cone foam surround rot got the better of them for the second time (one has the draw the line somewhere).
Barring the possibility of repair, it may be time for a new pair (or quartet?) of Hiquphons.
Craig
PS. It should go with out saying that one should always turn off ones amps and disconnect ones speakers prior to attempting disassembly/repair. Failure to do so will almost guarantee disaster.
[This message was edited by Craig Best on TUESDAY 26 March 2002 at 22:40.]
