Hi David, When you are dealing with 4 ohm speakers and you are running a long cable, first off the resistance of the cable actually becomes part of the total impedance driving the speaker.
The second thing to understand is that all speaker cables have a property known as 'Characteristic Impedance'. This is not the resistance or impedance of the cable, rather it is the property of the cable such that it will have its best performance when terminated by a specific impedance. For example, a cable with a characteristic impedance of 8 ohms will perform best when terminated by an 8 ohm load. Its actual DC resistance will likely be quite low as will its AC impedance, however.
Even if we were talking about a cable with a 4 ohm characteristic impedance, there are no speakers that are exactly 4 ohms over their entire range, so there would be termination errors. Most cables have a characteristic impedance that is much higher than 4 or even 8 ohms so there is a greater error that results.
The error is in the form of reflected energy which smears the waveform. This increases as the cable length is increased; a simple way to reduce the error is to shorten the cable- hence a good argument for monoblock amplifiers.
The second thing to understand is that all speaker cables have a property known as 'Characteristic Impedance'. This is not the resistance or impedance of the cable, rather it is the property of the cable such that it will have its best performance when terminated by a specific impedance. For example, a cable with a characteristic impedance of 8 ohms will perform best when terminated by an 8 ohm load. Its actual DC resistance will likely be quite low as will its AC impedance, however.
Even if we were talking about a cable with a 4 ohm characteristic impedance, there are no speakers that are exactly 4 ohms over their entire range, so there would be termination errors. Most cables have a characteristic impedance that is much higher than 4 or even 8 ohms so there is a greater error that results.
The error is in the form of reflected energy which smears the waveform. This increases as the cable length is increased; a simple way to reduce the error is to shorten the cable- hence a good argument for monoblock amplifiers.