Cable lengths

That inductance is measurable at audio frequencies.

If you look at the output of a typical solid state amplifier with an inductor in the output you can easily measure the change in the way a square wave is reproduced with and without the inductor when driving a capacitive load. Most speakers have a capacitive load angle somewhere.

So, it is highly probable that increasing the series inductance that the amp sees WILL have a measureable and probably audible effect within the "audio range."

Published tests have shown that this small series inductance found in cables will cause a small but measurable drop by 20kHz. This is different than the square wave effect I mentioned above, but does show a measured effect within the "audio range."

In general it is a good idea to minimize these effects in a system that you are trying to optimize. If you are not trying to put together such a system, it won't matter at all.

_-_-bear

I did a quick experiment to see what the effects of coiling up 8' of a 13' speaker wire up would be. I took a 13' speaker cable (12 gauge oxygen free copper) and measured the effective resistance over 20 Hz - 300 kHz. I then coiled up 8' of the cable which made the effective length of the cable to be 5'. The coil was about 4 loops in a 6" diameter. I then measured the effective resistance again. Each line of the data is in this format:

Frequency,
Resistance of straight wire (milli-ohms),
Resistance of wound wire (milli-ohms),
% increase of resistance:

20 36.38 36.65 0.74
30 36.72 36.92 0.54
40 36.7 36.93 0.62
50 36.72 36.99 0.73
80 36.79 37.23 1.18
100 36.87 37.43 1.50
120 36.94 37.64 1.86
150 37.06 37.96 2.37
200 37.72 38.5 2.03
250 37.45 39.03 4.05
300 37.63 39.55 4.85
400 37.92 40.48 6.32
500 38.2 41.34 7.60
600 38.46 42.17 8.80
800 38.95 43.7 10.87
1000 39.41 45.14 12.69
2000 41.06 51 19.49
4000 43.66 59.9 27.11
5000 44.84 63.77 29.68
6000 45.81 67.28 31.91
8000 47.66 73.9 35.51
10000 49.47 80.14 38.27
12000 51.32 86.16 40.44
15000 54 94.62 42.93
20000 58.36 107.76 45.84
25000 62.5 119.8 47.83
30000 66.55 131.05 49.22
40000 74.25 151.6 51.02
50000 81.9 171 52.11
60000 89 188 52.66
75000 99 213 53.52
100000 118 251 52.99
300000 255 505 49.50

I should mention that the data I posted is for one side of the speaker cable only. The data for the other side is similar. Therefore, the numbers can be doubled for a quick approximation. For instance, at 10 kHz, instead of a 40.44% increase in resistance, you will actually have an 80.88 percent increase, etc.

When I did my experiment, the coiled wire had a higher inductance and capacitance. For instance, at 10 kHz, the straight cable had 3.96 uH inductance and 227 pF capacitance while the coiled cable had 5.26 uH inductance and 249 pF capacitance. Instead of listing all of these values, I have only provided the "effective resistance." I would be happy to email a spreadsheet with all of the data to anyone who wants it.

Wow, nice Bufus, I never would have thought it made that much of a difference (furtively slinking away to uncoil his cables). :-)

Greg

Okay... so what is worse, coiling one speaker cable or having one side shorter?