Audio Systems: Church speaker system, mission critical system, unbalanced lines

Question
My priest asked me to repair a broken speaker wire,ie, connect the existing wire to a different speaker. Should I be concerned with matching the resistance of the speaker with the amplifier or are they all 8 ohms?
Also the speaker wire appears to be a balanced line.  Any problems or suggestions in soldering the two wires and the shield?
Thanks,
Bruno

Answer
Hi Bruno,

Well, whatever you do, make sure you turn the system off before attempting repairs!  You should definitely be concerned with matching the resistance of the speaker with the amplifier (we usually call this impedance matching). If your impedances are not matched, you can run the risk of having audio that's not as loud as it could be, or if it's the other way, you can actually blow out your speakers if they are not rated for the power you're putting through them.  Since this is a church, and was most likely installed by a professional, I don't think you have to worry about this too much, but you should at least examine a wiring diagram for the system to make sure that the speaker you are putting in the current one's place is similar to the current one. Most speakers have a sticker on the back that will tell you what kind of power they can take. If not, the manual definitely will.  A good article on impedance matching, and how to figure out what the impedance of your audio system is can be found here: http://www.peavey.com/support/technotes/concepts/impedance.cfm

As far as your second question is concerned, it might benefit you to temporarily take apart an existing speaker wire from the same system to see how it is wired.  Usually, balanced lines are used to eliminate electrical noise from your circuit. I don't know where your speaker lines run, but if they go near any source of EM interference, such as a fluorescent lamp or fan, using unbalanced lines would produce audible noise.  

With a "mission-critical" system such as this one, the most important thing you can have is consistency. All connections should be soldered the exact same way, and all speakers should be wired to the same specification. This makes it easy to troubleshoot in the future because you'll be able to make assumptions about how things actually are.

Hope this helps!