Long speaker wire run

[kse]

I want to put speakers out by my pool. Last year I did the Bluetooth speaker thing and the range at which the phone needed to be was way too short and the audio quality was barely better than a clock radio. So those are now gone.

So far this summer I have just been turning up the speakers on my deck loud enough to hear them adequately out by the pool. When I am by myself this is fine, but if my wife is in the house or on the deck I would be blasting her out.

I have two pair of channels going unused in my Sherbourn PA12-45 power amp. I would like to use it to power a pair of speakers (or two) out at the pool. The problem is, the run is an easy 150'. That's a rough measurement, could actually be as much as 170'+.

I have a ton of 14/4 leftover from when I wired my house. Would this be adequate enough to make a run that long? I would think there must be some degradation with a run that long, but this is for outdoor pool music so I'm not sure it matters....?

What do you guys think?

[Darksky]

14/4 = 11/2

[kse]

Jun 30, 2014 8:26:48 GMT -5 Darksky said:

14/4 = 11/2

[Deleted]

Should be more than adequate, IMHO. My folks have a similar situation re a long run by the pool. One thing you might not have considered, as they had an issue with little creatures munching through the wire, which created a short, even though the cable was buried in some mulch and light topsoil. Maybe run the wire through plastic or steel conduit.

[kse]

Jun 30, 2014 8:57:27 GMT -5 johnnyd70 said:

Should be more than adequate, IMHO. My folks have a similar situation re a long run by the pool. One thing you might not have considered, as they had an issue with little creatures munching through the wire, which created a short, even though the cable was buried in some mulch and light topsoil. Maybe run the wire through plastic or steel conduit.

When the trenches were dug to get power from the house to the pool area for the mechanicals, I pre-ran empty conduit for reasons such as this.

[DYohn]

Assuming an 8-ohm load, you'll need to run 10-AWG speaker wire. If the speaker impedance is less, you'll need larger wire. Or convert to a 70-volt system.

[kse]

Jun 30, 2014 9:11:19 GMT -5 DYohn said:

Assuming an 8-ohm load, you'll need to run 10-AWG speaker wire. If the speaker impedance is less, you'll need larger wire. Or convert to a 70-volt system.

Yes, 8ohm. What will the downfall be to the 14?

[KeithL]

The basic idea is that you don't want the resistance of the wire to be too high.... for two main reasons.

1) Speaker wire acts exactly like a resistor in series with the speaker. 14 gauge wire is about 2.5 ohms per 1000 ft (you have to count the full "round trip"), so a 150 foot run of 14 gauge wire will be about one ohm. This will cost you some power. With a 150 foot run of 14 gauge copper wire and an 8 ohm speaker - assuming it was really 8 ohms - the amplifier will see a 9 ohm load, and about 12% of that will be lost in the wire. With a 4 ohm speaker, the amp will see 5 ohms, and you'll be losing 20% of that power.

2) Since, from the point of view of the speaker, that resistance is added to the source impedance of the amplifier, it will reduce the damping factor - a lot. With an 8 ohm speaker, and starting with an amplifier with a very high damping factor, putting one ohm in series with the amplifier will reduce your damping factor to around 8. With a 4 ohm speaker the damping factor would be around 4. That isn't as tragic as it sounds, but it will make an audible difference with good speakers (the bass will get less tight, and almost certainly less flat).

In short, to interpret those numbers, assuming you're putting small-ish speakers by the pool, and you want them to sound "nice", but aren't expecting "really great audiophile quality sound" or gobs of super clean bass, then 14 gauge wire will probably be fine. (Anything thinner than that - meaning a higher gauge - would be really bad.) If you were putting speakers out there with really good woofers, or running a lot of power, then I would definitely go up to 10 gauge. Also, of course, if we're talking about an underground installed run, you should consider whether you may ever upgrade the outdoor speakers - since it would be a pain to upgrade the wire later.

If you have four-conductor wire and double up your runs, then the resistance will be halved; in which case the power losses I quoted would be halved and the resulting damping factor at the speaker would be doubled.

Jun 30, 2014 9:52:39 GMT -5 kse said:

Jun 30, 2014 9:11:19 GMT -5 DYohn said:

Assuming an 8-ohm load, you'll need to run 10-AWG speaker wire. If the speaker impedance is less, you'll need larger wire. Or convert to a 70-volt system.

Yes, 8ohm. What will the downfall be to the 14?

[Dark Ranger]

Jun 30, 2014 8:29:37 GMT -5 kse said:

Jun 30, 2014 8:26:48 GMT -5 Darksky said:

14/4 = 11/2

Darksky was saying that you can create two pairs of 11.2 AWG with the 14/4 cable. For example, you have four wires (say red, black, white, and green), and each wire is 14 gauge. To create 11.2 AWG, just wire two together for a +/- pair. So you could wire red & black together for the positive side and white & green together for the negative side.

I actually use 14/4 cable wired to 11.2 AWG for my own systems although my runs vary between 20 and 50 feet tops. For 150 foot runs, I'd definitely use 10 AWG.

[DYohn]

Jun 30, 2014 9:52:39 GMT -5 kse said:

Jun 30, 2014 9:11:19 GMT -5 DYohn said:

Assuming an 8-ohm load, you'll need to run 10-AWG speaker wire. If the speaker impedance is less, you'll need larger wire. Or convert to a 70-volt system.

Yes, 8ohm. What will the downfall be to the 14?

Besides power losses in the wire, you are also affecting damping factor. Adding speaker wire resistance lowers the damping factor of the amp. In most cases it's really not a problem, but in some it can cause issues with bass response due to raising system Q.

Here's a page with some great calculators for power loss due to speaker wire resistance.

www.bcae1.com/wire.htm