Ohm confusion and speaker wire

I set a up a new stereo receiver this weekend! After a few days I realized that I had 6 ohm speakers and the new receiver was 8 ohm. Unsure of how important this was, I panicked!

After consulting my receiver's manual, it turns out "the factory default for speaker impedance is 6 ohm." It certainly put me at ease.....but also got me wondering. Why make an 8 ohm amp and then set the speaker impedance for 6 ohm?

With my old setup, I had never given ohms a thought. In my ignorance, I bought 16 gauge speaker wire. Does this even matter? What gauge is best suited for 6 ohm speakers?

As always, thanks for being a valued resource. This forum has been an incredible guide through the world of audio!

 

A speaker's impedance, while it may nominally be rated at 4 ohms, or 6 ohms, or 8 ohms, or 16 ohms, or whatever, isn't a fixed number like a resistor -- it's not like it just presents a 6 ohm load and never changes. It changes with frequency, and sometimes a lot (and when you get a multiway speakers system with different speakers and a crossover network of resistors, caps and inductors, the impedance profile can get even more complex). When speaker impedances go particularly low, they can demand a lot of current of an amplifier while an amplifier may or may not be able to deliver, and depending on the output impedance of the amp, the amp may not control the cone excursion as well. That nominal impedance figure can be pretty misleading too. If a speaker dips to three ohms at a frequency like 100 Hz or something where there's a lot of current hungry energy and musical activity that's going on, but if the impedance stays high throughout the rest of the audio spectrum, like well above 8 ohms, that might wind up being called a nominal 6 or even 8 ohm speaker by the manufacture, but really should be treated more like a 4 ohm speaker were you'd want to make sure your amp could deliver sufficient current into a 4 ohm load.

You really need to look at a chart of the impedance curve of the speaker -- the impedance peaks and dips charted across frequency -- and the phase angle to get a real sense of how easy or difficult the speaker load is to drive, and then, if you do have a challenging speaker, you need to see if the amp is rated into low impedance loads. In most cases though today, if you have a solid state amp that can comfortably drive a 4 ohm load (look to see if the power ratings double going from 8 ohms to 4 ohms), and you don't have a speaker with a super unusual impedance dip (see if the speaker manufacturer identifies minimum impedance, not just nominal impedance), you're not going to have a problem. (If you're using tubes it's a whole different bag.)

In terms of speaker gauge, while theoretically with the kinds of currents were talking about in audio, speaker cable gauge shouldn't matter all that much unless you're using long runs of cable, I never use less that 12 AWG cable myself.

 

Usually, a small mismatch between the amp's stated impedance and the speakers' is unimportant. The impedance of any speaker varies by frequency, anyway. As to the amp, tube equipment tends to have output transformers, and it provide outputs for speakers of various impedances. Solid-state does not, and usually has only one output.

Typically, measurements of amp performance are at 8 ohms. That's why the amp is "8 ohms" -- not that it can't drive various speakers, but that the official measurements refer to an 8-ohm load.

In wire, the gauge of the wire gets smaller as the wire gets thicker. Some heavy speaker wire is 9 gauge, and 16 gauge is about the lightest one typically uses. Unless you have a very long run, it may not matter very much. With a megabuck system, such differences can make a small difference (known to audiophiles as a "very significant, earth-shaking difference"), but with a typical receiver and the speakers it's used with, it won't make much audible difference, if any.

If you want to experiment, something like this would let you try heavier wire at a low price: Amazon.com: Monoprice 102747 50-Feet 12AWG Enhanced Oxygen-Free Copper Loud Speaker Wire Cable: Home Audio & Theater »

Hope that helps!

 

I once brought out my home speakers ( 8 ohms) and hooked it up to my car deck (4 ohms). It sounded fine, but wasn't as loud as the car speakers. No issues...

 

Thanks for the replies! It's nice to have a better understanding of HOW gear works!

Also nice to know that speaker wire gauge doesn't matter much. While my equipment is VERY nice to me....it's humble and modestly priced. Still...I may experiment with 12 gauge at some point!

 

Try to move beyond gauge being the main focus of speaker cable. The choice of metal used, the configuration, the dielectric, etc. should also be considered.

I also suggest you avoid that Monoprice cable as it is known to oxidize.

 

Great advice!

 

I didn't know that. Thanks for the tip.

 

In theory it doesn't matter much for short lengths of cable, low impedance amps (like solid state amps), and speakers with impedances that don't dip super low. But in practice, I'm not sure that's the case. I swear I've heard differences between one-foot speaker cables of different gauges (and, yes, geometries) used in combo guitar amps. And, as noted above, things other than gauge -- all kinds of things from cable geometry to conductor and dielectric materials to conductor grain structure -- are more the things that audiophiles get worked up about. At the most base line, resistance matters, so a given length of 12 AWG cable is going to have a lower resistance than the same length of 16 AWG cable. Inductance matters -- so maybe Litz cable is a good choice for a speaker cable geometry. But so much of what's going on with a hifi speaker has to do with the interactions between the amp driving it and the complex, changing load it presents the amp, as well as the length of the speaker cable, that it's hard to tell someone just dipping their toes into audiophilia that there's some kind of simple rule you can always apply other than this one: use good copper that's well insulated and terminated so it doesn't oxidize, I say go to to 12 AWG because, what the hell, can't hurt at any kind of reasonable home length, and keep the lengths as short as possible. To me that's a kind of baseline for best practice. If you want to get into what differences copper grains structure may or may not make, and super low inductance cable (and the potential problems it may present because of very high capacitance), and all kinds of different geometries, and questions about reflections and time smear from characteristic impedance and energy released from the dielectric, and everything else you'll find down the audiophile cable rabbit hole, be my guest, but I say, if you're just starting out, don't go down that rabbit hole, and even later, there are things to get obsessed about -- like speaker and listing spot positioning, and room treatment -- that will make much bigger differences than differences of speaker cable with a average load speaker and powerful enough class AB solid state amp.

 

Fill out your equipment profile if you want the most accurate answers and the best help from those who can provide that. Not every piece of gear in question will net the same answer. One thing that I can say without knowing what you have is that money otherwise spent on speaker wire is better spent on a speaker upgrade.
-Bill

 

Maybe I'm getting OT here, but I agree that it's a matter of priorities. Though wires and cables can make an audible difference in many systems, I've almost never found the difference musically significant, or comparable to differences from changes in seating position, speaker position, or acoustics. (The one exception in 50 yrs of audiophilia was banishing some high-capacitance wires feeding electrostatic speakers.) Of course, it's best to use cables well-assembled from quality components, but those are available at reasonable cost.

The sort of differences made by expensive wires are, IMO, best addressed after everything else in the system (including the speaker-room interaction) is as close to perfect as you can get it. Before then, it's usually more cost-effective to spend the money on better gear, room acoustics, or even more music. Once the system is near to perfection, and if the bank account allows it, it's time for fancy cables, cable elevators, pucks, magic gongs, and so on.

But one thing about priorities is that everyone has his own set...

 

Great idea! Just filled out the profile!

 

This is key for me! I may upgrade the cartridge on my TT....after that, I have to be content with my system.