At 14 gauge it would need to be over 500 feet long to be around 12 Ohms.
If the speaker’s impedance changes markedly with frequency  as speakers tend to do  a couple of ohms in the speaker cable would be a bad thing indeed. It would form a voltage divider whose values vary with frequency. That would change the frequency response in what you hear from the speakers. (I mean it would change it objectively, not in some magic audiophile way.) 
Your speaker’s output would deviate and track the impedance of the speaker instead of the original frequency response. It would be a lot like using a tube amp. While you can experiment with this, please keep the wattage of any resistors in mind. I’d stick to 10W or higher for low  mid level experimentation. I also want to point out that speakers with high resistance also heat up. Attempting to use undersized speaker cable, like 18 gauge or thinner, with large amps can be a fire hazard. 
Why? Because there is a cable that seems to get a heavy amount of interest here, currently a thread running on it, and guess what, depending on length, it has about 12 ohms of resistance. That's missing from the marketing blurbs, and of course it is not in any online review. Lots of positive reviews (not all), and of course it will be a very audibly different cable from any other cable. This is one case where there is no question, the difference will be audible. However, if you paid big bugs for a speaker with a great frequency response, or big buck for an amplifier with a low impedance output, then using this cable will negate both of those things. Taking a quick look at some impedance curves on Stereophile, I would say most speakers have a rising impedance in the midrange (13K), a dip in midbass(80300Hz), and then a big rise at low frequency. What happens at upper frequencies are all over the map. Just looking at a few Magico, one rises to 6 ohms then up to 8. One stays near 4. One Tannoy rises up to 1620 ohms. If my interpretation is right, midrange would appear louder in most cases, midbass a bit subdued, maybe a bit more deep bass, and highs you are rolling the dice. If you have a low impedance speaker, my math says up to 2+ db changes in the frequency response. To me it looks like an expensive resistor. 
@deludedaudiophile  As you increase the amplifier's effective output impedance the effective frequency response of the speaker would track the impedance curve. 
@deludedaudiophile
8 feet of Blue Jeans Cable (Belden)  .6 15 feet of RCA zip  .3

I've concluded audiophiles are crazy. You can sell them anything if you make it expensive enough and get some guy with no qualifications to say on YouTube that he likes it. Then people will like the sound on one album and one system and say it blows everything else away. Eventually a wacky "theory" {completely unsupported by meaningful data or known theory of electronics) will appear to explain why it's better. After a while, the owners will sell it and move on to something else. Sorry, I must have indigestion tonight. 
No one has mentioned the potential audibility of the loss of woofer damping a series resistance of several Ohms would have although Erik and Mike circle around the fact. Of course plenty of “speaker selector” boxes have been sold and used by nonaudiophiles that feature beefy 3 Ohm series resistors. 
You can measure, but the figures I posted are accurate. They appear to sell 410 feet versions. The figures I posted are for the total loop (both wires). They are not buying them because of the resistance because they don't even know it is there. They are liking it because of the resistance. It would swamp every other property of the cable. I think Eric is right, it is a tone control that cannot be changed. If the most common change is to raise the midrange, is that not normally a change that people prefer at first? I don't know if that would be a long term preference.

I went to their website because the construction looked really interesting. It piqued my curiosity. When I read their marketing information, things were not adding up for me. My background is solid state physics and material sciences for semiconductors and batteries so I live this stuff (materials, not cables). It did not take long to narrow it down to what the base properties must be, what the likely material was, and important, that the material would be high resistance. That resistance is missing from the marketing material.

Of course, @crustycoot is correct that a couple of ohms of speakercable resistance will degrade the realized damping factor considerably. The nominal damping factor is usually computed DF = 8 / Z where 8 is the assumed impedance of the loudspeaker, and Z the output impedance of the amplifier. So you would achieve a nominal damping factor of 200 (not out of the ballpark for a SS amp) with the output impedance of the amp being 0.04 ohms. If you add 10 feet of Belden 5T00UP, you’d add another 0.01 ohms, and the effective DF would be 160. If you added 2 ohms of cable resistance, the effective DF would be about 4. Some prefer an underdamped sound. P.S. I am prone to typos and simple math errors, so if I’ve made any, please point them out and correct them. 
@pmerendino, If these are 12 ohms, a standard good quality meter should get you close enough. Not perfect, but close enough. For inductance, back of envelope assuming 2 inch average spacing would be 400nH/foot. At 6" that is 1.1uH / foot. That's just first order equations. I could simulate it in FEA but hardly seems worth it. If my math is right that’s about 0.7 ohms impedance but at 20KHz and I have not been able to hear there for a long time. Back to my stereophile phase and impedance charts, the impact would depend on the speaker. It does not seem like a good design to allow the inductance to be so variable.
