"Old" Monster cables

[NileDB]

I own 2, 25-30 ft. old monster speaker cables with the red and black banana pins already on them. They're a giant gauge in clear coating. I don't see any discolorations anywhere. My questions:
Do they ever "wear out"?
These runs are way too long. Can I simply cut them down and put new pins/spades on? I'm not experienced with a soldering iron, so are any replacement connectors "screw on" and are they worth a ****?

 

[Chu Gai]

No, they don't wear out and even if it happened that you saw some green discoloration through the insulation it doesn't matter.
Indeed you can cut them down and terminate them how you like. Keep the pins or use whatever combination of bananas or spades you like. Both are available in crimpable or even compression style. You can always mosey on over to the Shack and see what's over there or you can head on over to www.partsexpress.com where you can just type in 'spades' in the search box and see a smattering of offerings. Like anything else, when ordering online, you might find s/h charges to be disproportionate with what you're buying so if you go that route, think about what else you're likely to need in the near future.

 

[Allan Jayne]

I would say use the cables as-is and just coil up the excess behind your receiver. 20 to 30 feet is not enough to degrade audio, given you say the copper inside the cables is nice an thick. Who knows, some day you may need 25 - 30 foot cables.

The only exception would be if the old connections were not soldered on in which case there is a chance the joints have become oxidized and your remaking the joints would improve things.

Video hints:
http://members.aol.com/ajaynejr/video.htm

 

[brucek]

Really? If I had a choice I would cut my speaker cables to length.

The speaker to power amp connection operates in the current domain. This is an extremely low impedance interface. The output impedance of most amplifiers is less than 0.1 ohms feeding a speaker and crossover system with impedances that vary from 4 to 8 ohms. You have to appreciate the upsetting factor that simple cable resistance and inductive reactance (particularly at higher audio frequencies) can add to this scenario even in relatively short lengths.

Because the speaker is in the order of 4 - 8 ohms, a long speaker run, particularly one of high gauge (small wire) can become an appreciable proportion of the speaker impedance and as such can affect a signal loss and change of system response combined with decreased system damping. The system damping formula is almost exclusively driven by the speaker cables impedance, which is a function of its resistance and inductive reactance (capacitive shunt reactance can be ignored here). It's really the main advantage (besides channel separation) in owning monoblocks. It allows the placement of the amplifier to be as close as possible to the speaker while using super short speaker cable.

Consider a 20 foot section of 12 gauge speaker wire at 20Khz.
Typical 12 gauge cable exhibits a DC resistance of about 1.619ohms per 1000ft. This resistance is not frequency dependant and can be calculated as to the loss you'll experience for every foot in relation to an 8 ohm speaker. Basic math.

Next value to consider is inductance per foot of the wire. A pretty good estimation of inductance per foot for most guages of zip cable is about 0.2 microhenrys/foot. Yes, the higher the guage (smaller wire), the higher the inductance, but it's really insignificant.
Inductance (and capacitance) are both properties of wire that create frequency dependant resistance.
For inductance, as the frequency goes up, the resistance increases. This resistance is actually called inductive reactance - no matter. What matters is that it is a resistance that is in series with the speaker loop and it will create a loss.
The fact is, the higher the frequency, the higher the resistance caused by the inductance, and remember, the longer the cable, the more inductance 'adds up'.

For capacitance, since this a low impedance connection, we can essentially disregard it and the bypass reactance it causes. Capacitance is only a player in high impedance connections such as interconnects between preamps and power amps. It's too small an effect to be considered in a speaker connection.

Let's consider a 20KHz signal - upper end of the audio spectrum.

The DC resistance (DCR) is not frequency dependant and calculates to:
DCR = (0.001619) x (20 x 2) = 0.065ohms for 20 feet.

The inductive reactance (XL impedance) at 20KHZ is:
XL = [2 x 3.14 x (20e+3) x (0.2e-6)] x 20 ft = 0.502ohms for 20 feet.

So a 20 foot piece of zip speaker cable has an approximate impedance at 20KHz of:
@20KHz = 0.065 + 0.502 = 0.567 ohms.

So how is that significant in relation to an 8 ohm speaker:
@20KHz = [(0.567 / (8.0 + 0.567)] x 100 = 6.6% power loss in the extra speaker cable.

Assuming a typical solid state amplifier output impedance of .05 ohms, this 20 feet of cable will also lower the damping factor quite a bit. Using DCR only in the formula (since damping becomes significant at lower frequencies), it lowers the damping factor to:
(speaker impedance) / [(amplifier output impedance) + (wire impedance)]
= 8.0 / (0.05 + 0.065) = 69

What's this mean? At 20KHz you can see that the inductive reactance is starting to overwhelm the formula and a loss is creeping in, evidenced by the 6.6% loss figure. It's becoming a low pass filter and can't be ignored. Remember these losses are in addition to the loss in the cut cable that you would use.

I suggest cutting the speaker cables to length......