One error I noticed, maybe someone already pointed it out, but any voltage applied to the output of an amp is reduced by the feedback divider the same amount as the gain of the amp,before it reaches the negative input so you dont need to add that 27db? of gain
The basics were ignored! The speaker cable is connected to the output of a power Amp. Those have a DF figure that define their output resistance. A mediocre figure would be 150. That equals to
an output resistance of 8/150=0.053 ohms. the higher the DF the lower the output resistance.
No.
Damping factor is a near meaningless term and doesn't define the output impedance, it is defined
using the output impedance and calculated relative to the speaker's impedance. It is a marketing, not an engineering metric. The output impedance of a feedback design is the intrinsic impedance of the output stage divided by the feedback factor.
But to feedback. This is critical. Feedback does not work at every frequency. As frequency rises the effect of feedback drops. This occurs for a range of reasons, but is required to be designed in to avoid instability. (This is control theory 101, and is true for any negative feedback system, whether electronic, mechanical or whatever.) At radio frequencies the feedback network has no effect. Indeed at frequencies much higher than audio you will see every feedback amplifier's output impedance rise until it reaches the non-feedback value. At RF energies, the impedance seen at the speaker terminals can be almost anything you care and will vary wildly with frequency.
So the cables are picking the signals, they're going against the 'flow' to the amplifier, they're getting transformed into the audible range and amplified and back into the speakers?
Yes. There is no such thing as "against the flow". As described in a number of posts earlier, amplifiers can and do receive perfectly audible AM transmissions. All you need to do is to couple the RF energy into part of the circuit where there is some form of diode effect (basically any transistor will do) and the audio component will be demodulated and appear as an audio frequency signal. The amplifier will treat it just the same as the desired audio signals, and send it, amplified, to the output.
RF comes in a huge range of wavelengths. Not unakin to the range of wavelengths we deal with in audio (just travelling at c, not the speed of sound in air). AM radio stations have wavelength of the order of a mile, down to 5GHz WiFi which are 6cm. The manner in which these travel in and around equipment is very different. As the wavelength drops they behave more and more weirdly. As the old saw goes, to a proper RF engineer, anything that will go down a wire is DC. RF will travel down things you don't expect. Making equipment tolerant to RF energy isn't trivial, and is an ongoing battle. Those FCC certifications you see on gear are a mix of requirements. Manufactures of RF emitting gear are required to ensure that they don't emit energy anywhere except in the designed for range of power and frequency. Avoiding emitting harmonics of your carrier frequency is the sort of thing they are worried about. But your consumer audio gear is simply required to cope with whatever it sees assuming all the emitting devices are operating according to their specification and rating.
Calculating things like impedances for RF against audio components is not trivial. You can't use the audio frequency values. At any given radio frequency something like a voice coil could have nearly any impedance. Crossover components similarly so. Self inductance in capacitors and inter-winding capacitance in inductors will typically result in total inversion of component characteristics. And as the frequency rises, audio value components just look like a dead short, and then swap to looking like an open circuit, and so on. As the wavelengths get short relative the lengths of wire the wires look like transmission lines and energy reflects.
Bottom line. RF is really difficult. Properly testing gear takes million dollar test facilities and lot of time. Some idiot on the innertubes claiming that braiding wires is a cure all is a perfect example of the Dunning Kruger effect. So stupid that what he babbles is not even wrong.
