In my last post on cables, one of the respondents replied with a couple of great links. One of them was to Roger Russell’s site on a discussion about speaker wire. In that article, he had a very useful table on wire gauges and maximum cable lengths you should use. I grabbed the table, reformatted it for GuitarGear.org. Here’s the table:
| Wire Size | 2 ohm load | 4 ohm load | 6 ohm load | 8 ohm load |
|---|---|---|---|---|
| 22 AWG | 3 feet max | 6 feet max | 9 feet max | 12 feet max |
| 20 AWG | 5 feet max | 10 feet max | 15 feet max | 20 feet max |
| 18 AWG | 8 feet max | 16 feet max | 24 feet max | 32 feet max |
| 16 AWG | 12 feet max | 24 feet max | 36 feet max | 48 feet max |
| 14 AWG | 20 feet max | 40 feet max | 60 feet** | 80 feet** |
| 12 AWG | 30 feet max | 60 feet** | 90 feet** | 120 feet** |
| 10 AWG | 50 feet max | 100 feet** | 150 feet** | 200 feet** |
The “**” indicate that in reality a 50 foot cable length is actually optimal.
I dig information like this because it’s a great reference for when I’m buying cables.
With speaker cables, what you’re concerned with is not capacitance, like you are with instrument cables. What you’re concerned with is resistance. You COULD use a material that has much less resistance than copper, like gold, but you’ll get much more bang for the buck by just going up a gauge (down in number). Personally, I just use 12 gauge wire for my speakers, and the lengths are only 4 feet, so I can use pretty much any load and be assured that I won’t create too much resistance between my amp and cab.
Guitar Gear 
That is very good info.
Also it makes a lot of sense that lower ohm loads would mean using a shorter or thicker wire set.
I was at a friends house that had a JVM 410 going into a 1960b cab. Just out of curiousity we tried it at both the 4ohm and 16 ohm settings. I could definately hear more low end at 4 ohms,
Any one that has worked with PA’s knows if you want more low end you need more power which you can get from your existing power amp by loweering the ohm rating (adding speakers) or add more/larger amps. What I’m getting at is that it makes sense that lower ohms means more current which causes the need for heavier wire guages..
BTW a 4 ohm load is a larger load than a 8 ohm load(that is it draws more current form the amp). Also it is extremely important on a tube amp to match the speaker load to the correct output transformer winding of a tube amp. This ensures maximum energy transfer and causes the tube load to be correct( also never run a tube amp without a load on the speaker out).
For solid state amps no output transformer is involved with the transfer of power to the speaker you only need to be concerned you do no exceed the power handling of the speaker output. These days it is not uncommon to see 2 ohm speaker load available on a lot of bass amps.
You should also be aware on high output amplifiers the current to the speakers can be lethal.
Ohms law
I=V/R
electric current (I) is equal to the Voltage divided Resistance of the load
P=V*I
Power P is equal to the Voltage times the Current(I)
Sorry for all the technical mumbo jumbo but this is why attenuators are required by some of us. An attenuator maintains the correct load on the amp while passing less energy to the speaker. Allowing us to run an amp in its sweet spot without destroying our hearing.