Originally Posted by blueisthecolour:
“Ok, let me set the question differently:
If you had, say, a set of Mission SX1 speakers and a Yamaha AS501 amp what speaker cable would you recommend? Would it matter at that level.
What about a set of SX2s and a Yamaha AS701?”
It's not so much about the gear on the ends of the cable unless it's a poorly designed amp or a speaker that exhibits large variations in impedance with frequency; it's the cable length that has to be specified. That's why your question still can't be answered
With speaker cable you are transferring power from one place to another. The ideal position to be in is to have zero power loss. However, since cable has resistance then there'll always be some power loss until such time as we invent room temperature super conductor materials.
Two major factors in determining the resistance of the cable are its length and the cross sectional area (CSA). The longer the cable length then the thicker it needs to be to offset the losses. Let's say I have an amp that's capable of 100W per channel, and I want to transfer that power to a pair of speakers 20m away, and lose no more than 5% of the power. I'd need a cable with a CSA of around 3.5mm2. Reduce the cable length to 10m per channel and the CSA requirement drops to roughly 2mm2. Put the speakers right next to the amp and use cables less than a foot long and you can get away with bell wire. (The above presumes an amp capable or driving an 8 Ohm load and speakers with a nominal impedance of 8 Ohms.)
So, one part of the answer is to make sure the cable is of sufficient cross sectional area for the length. If you're cable lengths are up to 15m per speaker then you should think about a 2.5mm2 CSA cable. For 8m per side you can use a 1.5mm2 CSA cable and still get the same power at the speaker. For <5m then a 1mm2 will be sufficient.
Things get a little more complicated when other factors such as the speaker's impedance plot is considered or what effect the cable capacitance has on a poorly designed amp.
For speaker impedance you'll normally see it expressed in Ohms. 6 and 8 Ohms are typical values for Hi-Fi speakers. What the figures don't tell you is that that number is a sort of average. The real value actually varies with frequency, and not in a linear way. At some frequencies the impedance could rise quite significantly; it's not uncommon to measure 16-20 Ohms. At other frequencies it might drop as low as 3-4 Ohms or even lower if the speaker is "a difficult load". The effect of the impedance falling is that it draws more current from the amp. Our 100W/ch amp running at full power in to an 8 Ohm load will be delivering 3.5 Amps. But when the speaker's impedance drops to 4 Ohms the current drawn virtually doubles! If the speaker were to get down to 2 Ohms then the current would double again to 14 Amps. This is why it's risky to use those old all-in-one surround sound speakers as a stop gap with you're new AV receiver. They're often a nominal 3 Ohm load to start with, so they'll drop lower than that.
Fortunately we rarely need to run amplifiers at their maximum power outputs; as long as the speakers are reasonably efficient then just a few Watts is all that's required to make enough noise to satisfy.