Audio Systems: understanding ohms, speaker load, wattage ratings

Question
Hi, I have been asked to upgrade some speakers in a pub, they currently have an amp and 4 wall speakers, I intend to simply replace the current speakers with better quality slighter higher wattage speakers.

But some of the speakers I am looking at are 16 ohm and some are 8 ohm, I do not really understand ohms and do not know which ones to choose.

At the moment I do not know the ohm rating of the amp I will check that if necesary. The speaker will be two on each channel.

I do not know how they are wired as all the wiring goes into the ceiling I think each speaker is wired directly into the amp (2 into each channel)

Thanks very much for your time

Chris

Answer
It is a very simple matter.  The impedance of the speaker load (ohms) should match as closely to the amplifier without going less.

Example: Let's say the amplifier rating is 8 ohms minimum.  That means the speaker load should not go less than 8 ohms or it can cause damage to the amplifier.  If you used two speakers on that amplifier and they were 16 ohms each and they were connected in parallel you would be perfectly matched.  Or, if you had two speakers connected in series that were each 4 ohms that would be perfectly matched.  And so on.

So, you must find out the rating of the amplifier and connect accordingly.

You can easily trace out the speaker wiring by using an ohmmeter; they are cheaply purchased at any electronic parts house like Radio Shack or others.

Now, to wattage;  the wattage ratings of loudspeakers is sort of like pure fiction.  Just because they are advertised at high wattage does not mean they are going to sound louder!  You must consider the sensitivity rating.  This has more to do with the sound output for a given power input than does the power rating.  So, to get the most sound you want to not only be able to handle more power, but you want to choose a system that has a higher sensitivity rating.  If the old ones were 88db and the new ones were 93db you would get a  sound that was about 2/3 louder for the same input power.  If you wanted better fidelity but the speakers you wanted were the same sensitivity or less you would then need to increase the power rating of the amplifier (by replacing it with a new amp!)

Does this make sense to you?  If not let me know more.

Cheers.