Trevor Wilson wrote:



Then use a relay fit for purpose. Fraction of the cost of a speaker repair.


**High Voltage (30 VDC) DC relays are quite expensive. Certainly more
expensive than mid-range bass drivers.


http://uk.farnell.com/te-connectivit...20a/dp/1386559


** Such a large and expensive relay is quite impractical for use in a domestic hi-fi amplifier - also note that it needs powerful magnets for "magnetic blow out" of the arc to meet the 125V spec with DC.

A simple triac "crow bar" gives low cost, very effective DC protection for speakers - but surprisingly few amps have them fitted, the Quad 405 being an exception.


..... Phil