How much capacitance on speaker cable?

[pro_crip]

I was planning on making some speaker cable using silver ribbon (probably the kit from vacuum state, I wouldn't know where or what to source the ingredients) and read that ribbon has high capacitance. Would that be a problem for paramounts (300B version)? Thanks for listening.


Rich

[mhardyman]

Don't think it will be a problem as such.  Capacitance issues crop up on interconnects especially on the differences between analog and digital and the different requirements of each.

This lifted from the BlueJeansCable site:

"Speaker cable is a bit different from a lot of the interconnect cables we handle, in several respects. Because speakers are driven at low impedance (typically 4 or 8 ohms) and high current, speaker cables are, for all practical purposes, immune from interference from EMI or RFI, so shielding isn't required. The low impedance of the circuit also tips the balance of concern from capacitance, which is important in interconnect use, to inductance, which, while a concern, can be controlled only to a limited degree. The biggest issue in speaker cables, from the point of view of sound quality, is simply conductivity; the lower the resistance of the cable, the lower the contribution of the speaker cable's resistance to the damping factor, and the flatter the frequency response will be. While one can spend thousands of dollars on exotic speaker cable, in the end analysis, it's the sheer conductivity of the cable, and (barring a really odd design, which may introduce various undesirable effects) little else that matters. The answer to keeping conductivity high is simple: the larger the wire, the lower the resistance, and the higher the conductivity."

What are your interconnects?  That's where the real magic and damage happens as far as I'm concerned.  I picked up two pair of the Silver Interconnects from HomeGrownAudio and couldn't be happier.  The 10-gauge stock cable from Blue Jeans serves very well.

[ssssly]

Depends on how high the capacitance is. If the capacitance or inductance of a speaker wire is high enough it will start acting as a crossover.

This is pretty rare though. And normally only becomes an issue in very long runs of wire.

[Grainger49]

ssssly's point taken a little further, the crossover has capacitors in it.  The wire is not likely to be the major reactive component attached to the amplifier.

[pro_crip]

Ooops, didn't give out enough info. I think. There's no crossover to worry about, I'm going to use a full-range speaker. Since I shelled out $60 for Allen Wright's book I plan on making one of his IC recipes. In his recipe for the silver ribbon he mentions, in an aside, that the ribbon has a high capacitance but if your amp has enough current to drive it it shouldn't be a problem. My problem is that I don't know what kinda current the Para's push and I wanted to make sure they have enough to make the project worthwhile. I'm aware there is some HF roll-off with the ribbon but I think mother nature has taken care of that for me (I'm sure my ears have suffered their own roll-off by now). Thanks for listening.


Rich

[Paul Joppa]

Naturally, the only technical answer would be to either specify the maximum capacitance, or calculate the effect of the actual capacitance. In both cases, you'd have to determine the capacitance of the cable to make any sense of the answer.

Here's an example. On the 8 ohm tap, a Paramount will have about 3 ohms output impedance. It would take 1.3uF to cause a 1.0dB loss at 20kHz. You can find the formula for capacitance on wikipedia at

http://en.wikipedia.org/wiki/Capacitance

Usually, the only problem with speaker cable capacitance occurs with amplifiers that have a lot of feedback - i.e. transistor amps and some high-feedback push-pull tube amps. A capacitive load can drive the feedback phase far enough to lead to oscillation, sometimes at ultrasonic frequencies - you don't hear anything, but there's smoke coming out of your tweeter...