Audio Systems: understanding ohms, power rms, ohm stereo

Question
Hi, I have been asked to fit new speakers into a pub for a freind, but I do not understand ohms, and I have tried to learn it on the web but I just dont get it sorry.

they have a Acoustic Solutions SP103 2 x 40W RMS Mixer Amplifier rated at 4 ohms

I wanted to replace 4 of the currently installed speakers with these:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=23...

I need to try and follow the wiring that goes into the ceiling but I am quite sure that each of the 2 channels has two speakers wired in parralel.

can I add these 4 8ohms speakers 2 on each channel in parrallel on a 4 ohm amp please?

If it turns out that the speakers are wired in series would it still be OK to do this?

many thanks for your time in advance

Chris

Answer
Your friend really should find someone that already knows this stuff but at least you have the presence of mind to ask 1st, so I will gladly try to help you. :)

Be sure you maintain proper speaker phase for each channel.  We do not want one speaker cone going in while the other speakers' cone is moving outwards!

1)
"can I add these 4 8ohms speakers 2 on each channel in parallel on a 4 ohm amp"
As long as it is only 4 speakers total (2 per channel), your plan will work.

These speakers will need a lot of power to get loud since they are only rated to put out 88 Decibels at 1 watt. Splitting the 40 watts per channel so that each speaker will get at best around 20 watts each.

2)
"If it turns out that the speakers are wired in series would it still be OK to do this?"
The idea is to stay within the amps' allowable impedance 'range'.
All I can find on that amp is:
Power RMS 40+40W @ 4Ohm
Power RMS 30+30W @ 8Ohm

So, unless the owners manual specifies that the amp will safely drive 16 ohm, stereo loads, you would NOT be able to run series with 8 ohm speakers.

If you need help with proper speaker phase setup, please let me know.

JM<