:Hi all, : :I'm performing some high temperature testing in an environmental :chamber on some speakers. The chamber must remain closed during the :duration of the test, so I won't be able to hear if the speakers are :working. : :I want to be able to recognize if the speakers have failed (open :circuit). I'm supplying the speakers an output from an amplifier that :is fed with pink noise signal. : :Ideally, I'd like to make a circuit that would sense an open load, or :measure the speaker deflection using an accelerometer. : :I don't need to monitor quality, just operation, or more precisely, :malfunction. : : : :Any ideas?
Unless the speakers you are proposing to use are specifically designed to operate in a high temperature environent then you could get an extremely distorted response from the unit under test WITHOUT the voice coil actually going open circuit. It would therefore be wise to monitor the audio quality so use of a microphone would be mandatory.
The combination of the different materials and the construction must all be designed to resist high temperatures while still operating in an undistorted fashion and continuing to give a long life. Failure of either the voice coil suspension or adhesive or the diaphragm suspension could mean the speaker is virtually useless without the voice coil going open circuit. I doubt you will find all of these characteristics in off-the-shelf speakers designed for the domestic environment.
High temp speakers are not common, but one company does make a 6" unit which it claims will operate in close proximity to vehicle exhaust systems.
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