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An important note about the Flash demos/graphics on this site... The powers that be have deemed that the Flash content on web pages is too risky to be used by the general internet user and soon, ALL of the support for it will be eliminated (most Flash access was eliminated 1-1-2021). This means that no modern browser will display any of these demos, by default. The fix for now is to download the Ruffle extension for your browser. Ruffle Web Site. Please email me (firstname.lastname@example.org) to let me know if Ruffle is working well for you and what browser you're using.
If not most, many of the head units which are damaged, are damaged due to incorrect connection of the speaker output wires. This is especially true with units labeled as "high power". The output of a high power head unit is set up in a configuration. You remember how the bridgeable amplifier drove signal into both the positive AND the negative terminals of the speaker. You should also remember that the speaker received much more power in the bridged configuration (theoretically 4 times the non-bridged power). The same thing applies in a high power head unit. The biggest difference is that the radio has only the battery supply voltage (~12v DC) with which to work.
Motivating the Speaker:
Point 'A' indicates a voltage of approximately 12 volts on the negative speaker wire. Point 'B' indicates that the voltage on the positive speaker terminal is 0 volts. This means that there is 12 volts across the speaker terminals. Since the voltage on the positive terminal is less than the voltage on the negative terminal, the speaker would be pulled in from its point of rest. It would also be at its maximum inward excursion. Well... as far as it could be driven by this amplifier (before clipping).
At point 'C' on the green line the voltage on the positive speaker terminal is approximately 11 volts. The voltage on the negative speaker terminal is approximately 1 volt. The total voltage applied to the speaker terminals is approximately 10 volts. Since the voltage on the positive speaker terminal is higher than the voltage on the negative speaker terminal, the speaker would be pushed outward from its point of rest.
At the white line, the voltage applied to both speaker terminals is approximately 6 volts dc. Since there is no voltage difference across the speaker terminals, the speaker is in the center point of its travel (effectively at its point of rest).
And if you want a graphical representation of the cone movement...
6 Volts DC on Speaker Wires:
If you use Ohm's Law to calculate the power output:
Eight Channels of Amplification: