My receiver is located on one side of my room. My 3 front speakers are identical. The shortest run to hook up each speaker is 10, 15 and 20 feet. Is it best to use three 20 foot wires or cut each to length?
Theoretically, the length does affect the impedance of the wire (there is no time delay effect to worry about). However, unless your wire is very thin, and/or very coiled up, these effects are essentially negligible.
People forget that due to manufacturing and other factors, even two "identical" speakers can have impedance differences between them on the order of the impedance of wire.
You can minimize this small effect by ensuring you have a decent size wire to begin with (14 or 12 ga).
It has nothing to do with timing - it's resistance. Yes, even wire has resistance, but as stated in short runs for speaker hookup, using 12/14 Ga wire, there is no noticeable affect.
If you have several extension cords (typically 16 ga), try connecting them all together to a length of say 100 ft or more. Plug it in an AC receptacle. Measure the voltage at the receptacle and at the end of the cord. You will see the voltage has dropped. Does that mean we can't plug appliances into it. Absolutely not, their designed to operate in a range of voltage and you won't even notice a difference in the appliances operation. If you increase the gauge of the extension cord wire (16>14>12, etc), we will reach a wire size where the voltage at the end of the cords is the same as the receptacle. The other way to restore the voltage level at the end of the cord would be to stepup the voltage at the receptacle to accommodate the expected voltage drop.
So, to relate this to HT. if we use light speaker wires that brings the wire resistance into play, we must add more power from the rcvr to make up for the added resistance. Obviously, not efficient.
Bottomline: Use at least 14 gauge copper wire for typical HT speaker installations.
Red, you made one mistake with your extension cord example: with no load on the cord, even 10,000 feet of cord will show no voltage drop. The drop is dependent on the current through the resistance, not resistance alone.
The formula is: E(volts) drop = I(amps)sq. x R(ohms). Example: A wire with 0.2 ohms total resistance with a 10 amp load will drop (10 x 10 x 0.2 = 20) 20 volts. Halve the load or halve the resistance, the drop drops to 10 volts.
One other thing I'm surprised nobody mentioned. With the woofers drawing the majority of the load, and assuming there is a low-pass filter, the inductor is going to have a much higher DCR than any amount of speaker wire you will use. So, even within the bandwidth of the crossover, the DCR is going to be the dominant impedance in the path. Which actually could be a large percentage of the driver impedance.
Of course, you don't want to impede your HF drivers either, so I still wouldn't use #30 wire. But, I think any normal 14/16 guage wire should suffice. Also, it depends on your listening levels.
In theory, if you were to use too small of wire for the load, it will mostly attenuate the bass frequencies and overall SPL level. Therefore, forcing you to turn up the volume another notch or two to compensate. This would in turn increase the level of the highs. In effect making a speaker seem much brighter than it should. Hmmmm. . .
Assuming you use sufficient gauge, differences in cable lengths of 5 to 10 feet are highly unlikely to matter. 10 feet of extra cable coiled up behind the closer speaker might matter, especially if you have interconnects running through the coil.
In addition to the crossover circuit (inductors), there is the voice coil of the driver itself as a major source of DC resistance in the loop. Also, in addition to general loss of power, too much resistance in the cable results in an apparent increase of amp's output impedance from the speaker's aspect. That will reduce the damping factor, making the frequency response of the speaker start to mimic its impedance curve, with a boomy bass and other colorations.
So, using an appropriately thick speaker cable is important, and that is pretty much the ONLY important thing about speaker cables. See the "wire table" linked in the thread mentioned above.
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