Hi - technical question - what is the electrical effect on the rest of the drivers and the whole speakers sound if e.g. a tweeter is open circuit? Does it change the ohm value of the whole speaker? could it affect the volume of the whole speaker (apart form the lack of tweeter sound). Thanks.

It basically means that the amplifier will be looking into an open circuit above (if it is a blown tweeter) or below (if it is a blown woofer) the crossover frequency, bearing in mind the probable 6, 12 or 18dB roll off on the crossover. It shouldn't be a problem for ss amps. Older valve amps (e.g. Leak) typically had a 400 ohm resistor across the speaker terminals to stop the voltage going up due to no load (e.g. if the speaker cables become dislodged) and breaking down the insulation on the copper windings of the output transformer. A blown tweeter won't affect the other drive units and because of the low relatively (to the bass) low current probably not the amplifier.

Thanks, Peter - that really helpful. "Basically no effect on the other drivers but maybe an extra load on the amp." I'll look further into the system as a whole - it could well be the DAC which hadn't been used for a while or something else, but good to have the open circuit tweeter ruled out. Thanks.