Entertainment Center: TVs, Stereos, VCRs and DVDs - how to wire outdoor speakers

I have a whole-house stereo system with an Audiosource preamp and separate 150 watt amplifier. attached to this is a switching unit capable of handling 12 prs of speakers. currently there are 8 prs attached. I also wanted to add a pair of outdoor infinity speakers (outriggers) that are on an outbuilding approximately 150-200 feet from the stereo. I ran 14 gauge wire for them. When I attached the speakers to the switcher, the infinity speakers sounded poor (kind of static-y). I then attached them directly to the amplifier as the "b speakers" and they sound much better. The switcher with the other 8 prs of speakers is attached to the "a speaker" output on the amp. I have a couple questions. Will this setup overwork my amp if I have both the 8 house pairs on the switcher in the "a" amp output and the outdoor speakers on the "b" amp output at once? Would I be better served to get another amplifier dedicated to those 2 outdoor speakers? The outdoor speakers are rated at 8 ohms. Is that compatible with the amp since the switching unit is also attached? I don't know what the switching unit does to the impedance. I know it somehow matches the impedances for the speakers attached to it. Thanks
Dave

Good Evening, Dave4242:
Sigh! You have entirely too much time on your hands! LOL

One of the biggest problems I see is that you should be running #12 AWG on those speakers considering the power output and the distance. If you would like me to do the breakdown on the equations that provided that factor, I can. PtoP to RMS power versus voltage/current over a line loss per circular mil for #14 wire, etc.

What's important to this installation is that the amplifier sees one set of 8 ohm speakers no matter what is switched into the system. The switching system must provide equivalent resistances and equalization to provide 12 speakers to a single amplifier output. Mathematically, I can't see how it can be done equitably. There has to be some trade offs in power and performance somewhere.

If the system works okay with the speakers hooked to the "B" output, there is no violation to the amplifier. The amp has a set of dual final amplifiers and it appears that the "B" channel is running unattended. So, use it to run the new speakers. You just need bigger wire to do it right.

What do you say, Big Mike?

Smokey ;)

Shouldn't be a problem. But the bigger wire is a must! Now around here because of the ham radio gear I run all 12 GA stranded/tined copper with a double shield to keep out stray RF. Most electronic supply houses have wire like this that is designed for long runs etc. Sorry for the delay in answering Smokey, finaly got the new router today and am back in the saddle again...

Nice to know Bethlehem Steel found enough reinforced rod to design you a chair to hold you up to the keyboard. LOL

Smokey ;)

Omar the tent maker didn't know I wasn't using his brother in law for my chairs anymore... Now you've gone and told him... By the way, I aint out of shape... Round's a shape:)

Guys,
Thanks for your input on the outdoor speakers. Unfortunately, the 14 gauge wire is already in conduit underground, and it would be nearly impossible to replace. The underground run of conduit is only about 100 feet. The other 80 or so feet of wire is easily accessible (in basement and shed). Would there be a way to replace the exposed wire with 12 gauge and leave the 100 feet of underground wire as 14 gauge? The speakers will sound good for a while, and then the sound will start to break up some (sound like static). Is there any other way to fix this situation? The amp puts out 150 watts, and the speakers are able to handle 80 watts. I also have a Niles volume control capable of 60 watts. I have the volume turned up 3 notches on the Niles volume control (from zero position). Anything else you can think of? Thanks.

Hello, dave4242:

In answer to your first question, I would hook a complete section of #12 wire to the #14 running through the conduit, get on the speaker end, and PULL! No matter how you cut it, the #14 is too small for the job.

Second thing: These amps are rated at "peak" power as are the volume control you are writing about. A 150 watt amp delivers 75 watts per channel "peak". Actual power is
calculated at .707 of peak power so you are actually delivering 53 (and some change) watts to the system. This is the calculation we use to determine the wire size.

Conversely, your volume control is taking the full brunt of the power from the amplifier and is acting as a load to the amp. It is rated at 60 watts but is only capable of handling 42.42 watts of actual power. So, the volume control is "breaking down" and causing your problem. You need a volume control that will handle 75-100 watts (peak) or 53-70 watts true power. I prefer the 100 watt version because it offers some margin.

Building stereo systems can get a little messy if you don't know your Ohm's Law.

And, Big Mike's shape is round so we expect he will do a
"Round Two-It" and add some dialog to this post. :)

Smokey ;)

Smokey,
Thanks.
I'll go get some 12 gauge wire and a new volume control that can handle the power. Where might I find a control with those specs? I bought this one at Tweeter. Also, in my manual for the amp, it says that it is rated at 150 watts per channel or 400 watts monobridged. So is it still correct that it is only putting out 75 watts on the B channel or is it truly 150 watts peak. Thanks again.
Dave

Good Evening, Dave4242:

You guys offer just enough information to make things interesting, don't you?

150 watts "per channel"! Well, that puts a whole new light on things, doesn't it? Take all the figures from my last post and double them. You're still in trouble.

God, I wished you folks would tell me everything up front so that we don't have to guess at all final evaluations. Sigh!


Smokey

Smokey,
I apologize for not being more specific up front, but I don't understand alot of the specs, but I'm learning. Today, I took the volume switch out of the equation, and hooked the speakers directly to the amp. I then used the input control on the amp to change the volume of the speakers. They sounded even worse....breaking up, etc. They are capable of handling 80 watts. Were they receiving all 150 watts even though the inputs were turned down? I guess I don't understand the problem. On the one hand I have speakers that have a maximum power input of 80 watts. I have a 150 watt amplifier, so even if there is line loss with the 14 gauge wire, shouldn't there be more than enough power reaching the speakers? Again, sorry if this is simplistic. Is there a good refernce book/internet source where I can learn all this?
Thanks again.
Dave

Good evening, dave4242:
I apologize for spouting off! I have my share of frustrations with this forum. So, please, forgive me for my outburst.

Let's deal with Ohm's Law for a bit. Old George Simon Ohm developed this thing in 1849 and it has been a technician staple every since.

You have an amplifier that delivers 150 watts per channel. The amplifier is rated at "peak watts" or "music watts" and has little to do with what is going down the wire to the speakers. We deal in RMS (root mean square) or "true" watts. True watts are .707 of peak watts. So, your amp is pumping 106 watts of brute power down the wire.
You've got a speaker rated at 80 watts. Again, that is peak watts and not true power. So, you have a speaker that can actually handle 61.6 watts of brute power. So, you've been pumping 106 watts of brute power down the wire to a speaker that can only handle 61.6 watts. What do you think you did to the voice coil in that speaker? Fried it, perhaps? I'm surprised it even works at all. And, don't tell me you haven't turned up the volume control and unleashed that 106 watts on that poor 61.6 watt speaker. Smokey may be dumb but he is not stupid. LOL!

And, what are you doing to the final amplifiers on your stereo running all these mis-matches? You've put undo loads on those amplifiers to the point where they may have self-destructed. If you have distortion, I am not surprised.

And, trust me on this: You need #12 wire to the speaker. It's the price you pay for running all that power.

Smokey ;)

You need to run some type of shielded wire also, that long of a run is going to have some loss anyway. Spend the money and go to an electronics supply or Cat. No:2781268 from Radio Sham I mean Shack. Anytime you are making runs of this length you have to use a heavier gauge of wire to maintain the integrity of the signal. What you are hearing at the end of the line is a signal so degraded that the voice coil of the spkr. just hears/receives noise...

#12 wire will not fix this problem...
What's actually happening when you use long runs of wire such as in this case.... is that the amplifier is driving into a large capacitor...yes, capacitance is the big culprite here. Not resistance, but capacitance.
You can run 6 awg wire and you'll still run into the same situation.

I don't know what books you are using, lucman2. If you calculate Zo for a flat line at 20,000 Hz, it comes out inductive, not capacitive.

Smokey ;)