The signal travels from the amplifier as an amplified voltage and current through the speaker cable to the loudspeaker's speech coil. This causes a changing magnetic flux in the coil which interacts with the fixed flux in the gap between the coil and speaker magnet to create cone motion. This in turn creates sound pressure waves. Here the total harmonic and intermodulation distortion leaps up even further. A figure of 2% would again be very conservative. The non-linearities inherent in the loudspeaker to human aural system, makes any capacitor distortion look like a nit on a gnat's eye lash. First in the loudspeaker, the non-linear conversion of changing current to changing magnetic flux adds appreciable levels of distortion. Then the non-linear conversion of magnetic force to motion in the cone adds even more. The conversion of cone motion to sound pressure waves adds more still. Finally your own set of aural receptors, non linearly convert the sound pressure waves into electrical nerve impulses in the brain. You own ears add considerably more distortion than the difference between two capacitor types.In a more light hearted way, a much more serious distortion, more like an interference, occurs in some male brains. The noise from the numerous audiophile adverts and forums blurs the original enjoyment of the music. Thoughts of that nasty non-oil filled capacitor, loom in the affected brain and the relaxing music suddenly starts to irtitate. The truth is, the distortion, compression and background noise of most CD & Vinyl recordings plus the non-linear distortions in the loudspeaker-aural system, has hundreds of times greater effect on the original sound than the effect of changing a resistor or capacitor to an audiophile type. That non-faulty component is innocent! Leave it alone! and enjoy the music!When we service a typical vintage amplifier we often replace all the electrolytic capacitors and several resistors, not because they are 'better' so called, 'audio quality types' types but because the old ones have deteriorated. i.e., either changed valur, o/c, s/c, leaky, noisy, high ESR etc, etc.We insist on using high quality electronic components in all our service work for long term reliability but we steer clear of expensive audiophile types.
More examples of 'replacement for its own sake'
Lots of audio enthusiasts love changing new perfectly working decoupling capacitors with expensive audiophile types.. why? I don't now why!!A decoupling capacitor passes unwanted currents to ground away from the signal path. The important function is, to offer a low impedance path for unwanted currents e.g., noise, ripple, and signal bypassing. To effect this, the equivalent series resistance (ESR) and inductance must be as low as possible. A typical good quality low ESR 100nF 100V ceramic decoupling capacitor costs less than 5p. A well known audiophile capacitor of the same value and ESR can cost several times more. The difference audibly and electronically .... none! Those nasty ceramic capacitors we hear audiophiles ripping out of circuit and replacing by foil ones are superior for HF decoupling due to their inherently low inductance. You often see these sensibly shunting decoupling electrolytics to improve HF and spike suppression.
Solid state amplifiers have a very low output impedance relative to the speaker impedance. The output acts as a voltage source. Therefore, short lengths of thick twin copper wire to each speaker will make the best use of the amplifier's excellent damping factor. Valve amplifiers have much higher output impedance than solid state amplifiers, so the effect of the speaker cable resistance is much less pronounced. In both cases, ordinary multi-strand thick twin flex is perfectly suited. Don't spend £100s on speaker cables. Speaker cable should offer:1.Low series resistance compared to the speaker DC resistance to maximize efficiency (i.e. several hundred times less across the cable length). (The difference in resistivity between copper wire and silver wire is not at all relevant at the lengths used in even the most elaborate audio system. If a 3mm square section copper cable was 1km long ,it would have a resistance of 1.86 ohms or 3.7 ohms for twin runs. The same length solid silver twin run would have a resistance of 3.53 ohms. Thick multi-strand copper wire is perfect. Don't waste your money on silver or silver plated wire).2.Low inter-cable capacitance and therefore high capacitive reactance across the audio spectrum, relative to the loudspeaker impedance. (The inter-cable capacitance of decent low cost twin flex has a capacitive reactance way above that of the speakerimpedance across the audio spectrum, so it is insignificant. A 3 metre length of decent twin speaker cable costing £1.50 per metre has an inter lead capacitance of 150pF (Pico Farads). Even at 20kHz, the reactance is negligable i.e. 1/(2xPix150pF) = 53K ohms. at 1kHz it is over 1 M ohms!3.Low series inductive reactance relative to the nominal speaker impedance across the audio spectrum. (ordinary thick multi-strand loudspeaker twin flex has a negligible inductive reactance at audio frequencies)To achieve the best performance use inexpensive 80 to 200 multi-strand twin (figure of eight) cable and keep the length as short as possible ( i.e., a few metres).80 strand 0.2mm twin speaker cable is typically around £1.20 per metre!* From Pouillet's law:R = p x l /A'R' is the resistance in ohms.'p' is the resistivity of the metal used (copper 1.68 x 10-8) (silver 1.59 x 10-8)l' is the length of the cable in metres