So using that statement as an axiom a receiver with no speakers hooked up will run hotter than the same receiver with a small 20 gauge speaker lead over a 100 foot run?

Well, I would say that a direct short across the terminals (which would qualify as "no speakers") will make an amp run warmer than your 20 ga/100' example, if only for a "short" time.

Larry
www.fineelectricco.com

Suprised not much has been said about strand count. It's my understanding that a higher strand count is more important than the gauge. Supposedly the lower frequency info runs on the outer portion of the strand. So more strands equal more room for the info to get to the speaker which equals greater detail.
CMack

No, it's the higher frequencies that tend to gather on the surface of the conductors, due to what's known as the "skin effect". It even occurs at 60 Hz, but moreso at higher frequencies.

What actually happens is that there is a reverse voltage generated by the magnetic field that surrounds all current-carrying conductors, and this voltage is 'subtracted' from the regular current.

The greater the current, and the higher the frequency, the greater this inverse voltage, and because it's strongest at the conductors center, where the magnetic field is strongest, the result mimics a reduction in conductivity.

Whether the strand count makes a difference is debatable; each strand is not independent of the others, because they're in contact with their neighboring strands. Maybe the twist or braid pattern matters, too.

Larry
www.fineelectricco.com

there has been argument for years...uh ohhh, another bebate maybe?? :-), about this as well. Which IS actually better? I'm sure all our physics buffs will chim e in on this one again!

See the thread I'm about to start!

avdude

But that is not what you eluded to, I am not talking of a dead short here. If you run a drill on a cheap 100' extension cord at a job site the cord can heat up and blow the breaker out on the post. But the same run on a larger cord can and does run cooler with les chance of an over heated breaker. When it came to the statement I made regarding a larger speaker wire, (assuming all other variables are the same)I was trying to point out that a 20 gauge wire on a long run will throw the receiver into protection ( at high volume) before the same setup would on a 12 or 14 gauge.

No, you are mistaken with both of your premises. A drill on a too-small extension cord will heat the cord, sure enough, but overall, less power will be used. Because the source is a constant voltage, and you've increased the circuit resistance, the current is lower. That's simple physics (Ohm's Law).

The only way this could cause a breaker to trip is if the wire gets so hot that it heats the breaker due to proximity (conduction, convection, or radiation), and trips the breaker via its thermal response, but this is not relevant to our theoretical discussion.

Same with an amp: using too-thin wire will cause power to be wasted heating the wire, of course, but the amp will have a lower current output. However, to reproduce the same volume, the amp's volume control must be turned slightly higher to produce the same voltage at the speaker, which means the output voltage will be higher.

If this causes the amp to go into protect mode, the same thing would happen with no speaker (open circuit) at the same volume setting. However, due to Ohm's Law, a longer and/or thinner wire will reduce the power dissipated by the amp by behaving as a series resistor, and the amp will run cooler.

Whether the load is a speaker, plain wire, or a combination of the two, the current, and thus the wattage (at a given voltage) is dependent on the circuit resistance, period. The heavier the wires, and thus, the less the total resistance, the greater the current, and therefore power, the amp will put out.

Now, the phenomenon which causes an electric motor, fed by less than design voltage, to use more current (and overheat) is a different discussion. That still doesn't cause breakers to trip.

Larry
www.fineelectricco.com

Okay, now I would like to add a little something here:

If we're attempting to get the same loudness from our speaker after adding the 100' of 20 ga. wire, we have to raise the volume level (voltage output), which varies from your "all other things being equal" specification. Okay, let's do that.

Let's assume, for the sake of this discussion, the wire we're adding has a resistance equal to the speaker's impedance. That is like placing two speakers in series (except we can't hear one), or placing an 8-ohm resistor in series with an 8-ohm speaker.

Now that we're doubling the output voltage to compensate for the doubled circuit impedance, Ohm's Law tells us that the same current would result. Our amp, with a constant power supply voltage (unless it's a Sunfire) will actually be dropping less voltage across the output stage.

To be fair, if we need to drive a higher-impedance load, we should theoretically get an amp that will drive our given power level into a 16-ohm speaker, which would (guess what?) require four times the power rating as our first amp into 8 ohms. Now, that would run cool at 8 ohms.

Larry
www.fineelectricco.com

Larry,

I'm actually following what you're saying here...and that's VERY rare for me, but wouldn't it be like placing 2 8ohm speakers in parallel, not series?

avdude

no, larry has it right.

The wire's resistance is in series with the load. Trace the signal path:

Amp + to wire to speaker +, through speaker to speaker - to wire to amp -. A simple series circuit.

Two speakers in series would both shut off if any connection in the entire loop were opened. Think of low-voltage X-mas lights; one bulb unplugged (usually), they all extinguish.

A pair of speakers in parallel would allow either speaker to continue operating if the other were disconnected. Think line-voltage lighting; unscrew one, the rest stay lit.

Series resistances sum to a resistance higher than the highest single one. Parallel resistances always combine to become a resistance less than the smallest unit.

Larry
www.fineelectricco.com

Sooo... I just thought the circut breaker inside a receiver was thermal? If a smaller wire is used a higher volume setting is needed to extract the same volume level at the driver, this in tern would cause heat and the breaker to go into protection right?

When I said "run cooler" with a larger wire I assume that the room would be maintaining the same SPL, or the same load or required current, this thinking is incorrect then?


Im not trying to be a smart ass but that seems bass ackwards to me and what I have seen.

It is a matter of degree. Thinner wire increases resistance by about .1 ohms at the MOST. This translates into turning your volume knob a fraction of an inch. Hardly enough to send your receiver into protection. The "protection" switch is mainly to protect against a dead short at the load or extremely high heat such as when you stack equipment directly on the air vents.

A thermally-activated breaker responds to current, not voltage. An increase in circuit resistance reduces current. If voltage is increased to compensate, the most you'd end up with is the original current, even if at a higher voltage.

Larry
www.fineelectricco.com

what is a good site to get speaker wire these days for a good price?