Speaker cable gauge and amplifier power

Based on my limited understanding of electricity, sending electricity through a wire is like sending water through a pipe. Using a larger cable gauge or bi-wiring will increase the amount of current required from the amplifier.

It seems like there must be a way to optimize speaker cable gauge and length based on an amp's current and watt ratings. Lower powered amps would mate best with narrower gauge speaker wire, and a powerful amp would benefit from thicker wire.

Am I oversimplifying, or are there established guidelines based on calculations of current, capacitance, etc.?
It's more complicated than that. If one only considers wire gauge in relationship to output power, all the larger speaker cables are overkill.

Here is a chart:


Scroll down and see that 21 gauge will handle 1.2 amps of current. 21 gauge is about the size of doorbell wire.

Rather than trying to decipher this scientifically, listening with various speaker cables will provide a wealth of knowledge. I think you will find the design, insulation, RF rejection and terminations all play an equal role in the music, not just the wire gauge.
"Using a larger cable gauge or bi-wiring will increase the amount of current required from the amplifier."

The word that has you pointed in the wrong direction is 'required'. That's not the way amplifiers work. The drive Voltage creates a 'pressure' in the conductor; the amount of current that flows is simply the inverse of the resistance that Voltage 'sees'. If the resistance is low, high current flows, generating lots of power. If the resistance is high, low current flows, generating a small amount of power. The amp doesn't 'work harder' in either situation.

In an audio situation, the load resistance--the speaker--is relatively constant*, and what varies hugely is the Voltage presented to the amp by the upstream component, usually some form of preamplifier. If one part of the signal is 20 times higher in Voltage than some other, 20 times as much Voltage will flow into the speaker.

What will change with different gages of conductors is how much of that amplifier power will be absorbed by the speaker cable, because the cable always has some, however small, resistance. Current flowing thru a conductor that has resistance, and they all do, is converted into heat. That's just one reason** we try to keep the resistance of speakercable as low as reasonable possible.

Albert's last statement is correct--there are MANY factors that influence the sound of speakercable. The thickness of the conductors is just one.

* Folks, I don't need any reminders about impedance v. resistance, just go with the flow of my highly simplified example, pls. :-)
** Another reason is so that we reduce the amplifier's damping factor as little as possible.
I don't have a scientific answer but when I had dedicated circuits put in the electrician said that 15 amp capable power lines were massive overkill. I was asking for twenty, he said if you pull over 7-8 amps that would be remarkable. And I use 400wpc SS monoblocs that are fairly high current on separate lines of course. That being said I have seen ads that say you should have 20 amp capabitlity for some really monster amps which I can't afford. So I settled for extra 15 amp lines instead of fewer 20s. I have never had any obvious problems.
I agree with Albertporter, your ears are the best instrument.

I just replaced the small Nordost SPM speaker cable driving my subs with big (8 AWG) cables and heard a big difference...
As Albertporter stated, from a current carrying viewpoint all speaker wire size is overkill. I must admit that I have gone along with the heavy wire idea, although I have not used any of the specialized speaker cables with exotic construction.

Recently I tested some Nordist flat cables vs zip cord, and had to admit there was a very obvious difference. My plan of action is not to purchase $6000 worth of wire, but rather to purchase fan-free monoblock amps that I can loctate just inches behind my MG1.6 speakers.
Thanks for those responses. Jeffreybehr, in particular, addressed my question helpfully.

I certainly agree that the best way to pick a cable is to audition it in your system. I just thought I might be able to limit the number of choices based on this set of factors.
Here is my opinion on this.....as Albert Porter said, the gauge of most speaker wire is overkill - strictly considering the insulation breakdown point. I other words, 16 awg wire can easily pass 15 amps of current without melting the insulation and causing a short or even a fire. However, from an audio perspective, wire needs to pass a lot of transient signals to sound good (fast, short-term power demands). I my experience I have found that the series inductance of the wire has the most influence on sound. Inductance resists current flow, so wires with lower series inductance values will pass short-term, transient signals better, resulting in better sound. That said, I agree that the results should be audible, which is the ultimate test of any component. :o)
One thing that I found interesting is the wire guage used INSIDE speakers from the terminals to the drivers. We hook up our 8-ga hoses to speakers that use 16 or even 18-ga internally. This renders anything larger before it moot. So unless you need 25-plus ft of speaker cable, then the issue of voltage drop (not current delivery, BTW) should not be a factor in the size of the speaker cable.
The resistance of a conductor depends on the length use and the cross sectional area. More precisely, it is computed this way: R=p(l/a)
p=resistivity of the material(ie. a constant for copper, silver, etc.)
a=cross sectional area

In theory, if the length is short and the cross sectional area is large, the resistance comes out low.

In audio, the response of the resistance value of speaker cables are greatly enhanced, reduced, or in general influenced by the interaction of their characteristic impedance(because we are talking AC) to that of the passive crossover use which can result in either purely resistive (preferable), inductive, or capacitive in nature.

IMO, this is the reason why we hear difference in wires and nothing else. Unless of course you can teach electrons where to go and what to avoid.

In the end, no one can tell you what will suit your ears better. If measurements is the bread and butter, then the shorter the wire and the bigger the cross sectional area the lower the resistance of a wire which leaves the cable electrical parameters negligible and the speaker crossover to be the one who dictates the nature of the impedance seen by the amp.
If you believe "pipe size" is that important, giving a cable like Audience AU-24 Speaker cables a spin can be very surprising. I used them with a Pass X-250 driving Revels for a couple of years and STILL remember my shock at how they outperformed the garden hoses I was using at the time.

It's like Albert said- MANY factors go into cable design.
These are all interesting and enlightening responses. However, they have strayed a little from my original question. I was wondering about the interaction between amplifier and speaker cable. Does the output of an amplifier change based on the size of the speaker cable used (assuming all the other factors involved in cable design are held constant)?

For example, say you have an amp that produces 60 watts into 8 ohms, use an 8-foot run of speaker cable, and a pair of 8-ohm (nominal) speakers. Wouldn't the output of the amplifier change based on the resistance of the wire?

According to Albert Porter and other posters, even relatively thin speaker cable will pass higher amounts of current than most home amplifiers generate. But are there other ways in which using a thicker wire might affect the performance of an amp?
According to Albert Porter and other posters, even relatively thin speaker cable will pass higher amounts of current than most home amplifiers generate. But are there other ways in which using a thicker wire might affect the performance of an amp?

I was trying to inspire you to think beyond wire gauge.

I don't disagree larger gauge might be better, my favorite speaker wires are about 12 gauge under all that outer wrapping.

Thicker wire effecting the amp is perhaps the wrong way to look at it. The wire is passive and always lossy in relationship to the best ability of the amp. The best a wire can do is move most of the energy to the speaker with as little damage as possible and hopefully not picking up too much RF, vibration, inductance and other problems in between.

What I'm getting at is two identical wires (gauge wise) can sound totally different but not necessarily because it's effecting the performance of the amp. More likely it's showing the personality of delivering the energy to your speaker. Sure, things like capacitance and resistance are real and effect the sound but there are other things that are not so easy to measure.

When we have a perfect way to move that energy, there will be no need to discuss wire any longer.

Basically, choosing the lesser evil in wire is like choosing other compromises within ones system.
Albertporter...As Sean (the missing Sean) has told us many times, some wire with exotic construction CAN affect the power amp in undesirable ways unless terminated with a Zoebel network. I don't think that cables can do the opposite...make the amp work better.

The name of the game is hi-fi. Our concern is the signal riding the current and not the electricity . Of course clean power will carry a clearer signal, but that is easier said than done. Hi-fi claims that the 1st watt is the most important....So then 22 gauge would cut it. Mega weight and watt is mega loss . Did you ever measure what your system actually draws as far as power ,then what they say it can deliver. You'll be suprised .....
I don't think that cables can ...make the amp work better.

Yes they can. Properly designed cables will allow an amp to work more efficiently, i.e., better.


Kind Regards,
Ridgestreetaudio...Lots of luck!
Thanks Eld but we don't need to depend on luck.


An example of what I had in mind was the way Naim used to design their amps for use with a specific gauge and length of wire. Not only did they sound their best with Naim speaker cable, the amps could supposedly become "unstable" with the wrong wire.

I understand that they have changed their design so that speaker cable is less of an issue. I guess that most amplifiers are designed so that the cable doesn't affect the operation of the amp. Anyone care to take a stab at explaining that?

Also, if anyone can recommend a good primer on the physics involved in audio, I would appreciate it. I thought I knew a thing or two about how stereos worked before I started this thread.