Q & A

Sydney Morning Herald

Monday October 2, 2006

Rod Easdown

MATCH POINT

I bought three-way speakers in a charity shop and the mid-range driver in one does not work. Can I put in any replacement and does the driver need to be matched?

This depends on how discerning your ears are and how you listen to music. It's rare that all three drivers produce the same output level, so components in the crossover are used to compensate for the imbalance. For example, if the bass driver and tweeter each produced 90dB of sound, but the mid-range driver produced 92, the designer would include a resistor to drop the voltage so the mid-range produced 2dB less, making all three speakers the same. Unless your replacement mid-range speaker produces exactly the same output, the sound across the mid-range will be either too loud or too soft. But balancing the volume is just the beginning. Individual drivers have unique sonic qualities, just as speakers from different manufacturers, and even different countries, tend to sound different. If you listen carefully and you have an experienced ear, you will pick the tonal imbalance between different mid-range drivers on right and left - if you simply put music on in the background it will likely make no difference to you. Bear in mind that mid-range is critical. It's where most voices fall and where most musical instruments spend most of their time. You should check with the manufacturer to see whether spares are available. Otherwise, either remove the driver and try to find another (the internet is a good place to start) or take the speaker to a professional repairer and see what can be done there. You may want to ask about reconditioning the speakers at the same time.