Expert: Cleggsan - 6/5/2009

Question
I want to have speakers around a large swim pool at a country club. This is
mostly for background sound and not really loud sound. We bring in other
speakers for the loud, kids times.  

I am thinking of 8 100W speakers. See GS5 at
http://www.ticcorp.com/omni_speakers_gs5.htm  My guess is that I would
be running maybe 600 feet total of wire to have the speakers spaced around
the pool.

I'm having difficulty understanding the following:

1. Can I use "direct burial wire" rather than putting the wire in conduit?
Obviously safety for users is a big issue.
2. What gauge of wire should I be getting?
3. How do I determine what power (watts) (or other key specifications) I need
in an amplifier?  Do I need to do a calculation that would be affected by the
number of speakers and feet and gauge of speaker wire that I run?
4. Can I connect 8 (or more) speakers to one amp? The ones I have looked at
have connections for 7 speakers in the back and not 8. Do you have a
suggestion or source that would help as to how to wire (e.g., not all 8 in
series)

Thanks for any help.

Answer
1.  Yes, you can use buried wire if you wire direct to the amplifier. If you decided to use the 70v or 25v line solution you need conduit.  The advantage of 70v line is that you can adjust each speaker sound level by changing the tap on each speaker transformer.  The cost is considerably more. So, if you can live with the same sound from each speaker that would be nifty.

2.  Gauge of wire is not so critical since you are not pushing lots of power. You can use 18 ga up to 40 or 50 feet with no problem.  For greater distances go to 10 or 12 gauge.

3.  These speakers are 8 ohms and you want to drive 8 of them.  Therefore, if you used a stereo or two channel amplifier you could put 4 on each channel.  Four speakers in parallel would give a 2 ohm load to the amp.  Thus, you would need an amp that is comfortable with a 2 ohm load. Many of them are.

These speakers are quite low in sensitivity so you may need a little more amplifier power than ordinary.

4.  Yes, you can connect as many as you want so long as the load impedance does not go lower than the specification of the amplifier.  In your case you could purchase two amplifiers; each with 2 channel outputs. Then 2 speakers would be connected to each amplifier giving a 4 ohm load - ideal for most audio amplifiers.  And, amplifier power is relatively cheap now days.  Cheaper than long run copper wires!

You want to always wire the speakers in parallel across each amp; I don't recommend any series connections in a system like this because of troubleshooting when there is a failure of one of the wires or speakers - down the road of time.

You should look for amplifiers that will put out at least 400 watts total into a 4 ohm load.  An amplifier of this kind should not cost an arm and a leg.  For hi-fi class stereo receiver you can find them for $150 area.  Pro or semi-pro class will run more money, say $300 per amplifier.

Let me know if there is more.
C