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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: A question about the phase shift. posted by Tony Montana on October 8, 2003 at 13:37:21:
For a fast answer to your questions, check out Nelson Pass' website www.passlabs.com and look at his paper on cable parameters. For conventional parallel cables (zip cord) the inductance equals ofr exceeds the DCR at 3 kHz and exceeds the DCR at higher frequencies. It does indeed make a difference in longer runs. As a rule of thumb, if sum of the source impedance of the amplifier and cable impedance exceeds 5% of the minimum speaker impedance, it will make a just audible change in frequency response of the speaker. This "rule of thumb" assumes a ratio of minimum to maximum speaker impedance of 5:1 or greater, which is typical for most dynamic speakers.Since the amplifier source impedance is in series with the cable impedances, you cannot take the cable "out of context" by itself, but you must evaluate the amplifier and the speaker impedance as part of the issue. The model for this is that the amplifier and cable impedance form the upper arm of a voltage divider, and the speaker is the lower arm. To assess the frequency response at the speaker input and, therefore, the effect on speaker frequency response; you must compute the divider ratio at each of many frequncies over the entire bandwitdth from 30 Hz to 15 kHz. If you look at the measurements in Stereophileon amplifiers, you will see the effect of a simulated speaker load on the amplifier as compared to pure resistive loads.
Jerry
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Follow Ups
- Re: A question about the phase shift. - Bold Eagle 19:31:30 10/31/03 (0)
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