Speaker Impedance, Power Handling and Wiring
The speaker ohm rating is an indication of the speaker's AC impedance, which varies with the frequency of the input signal. This variation of the speaker's impedance can be seen on the speaker's spec sheet impedance curve. This is why the spec sheet indicates this speaker to have an 8 ohm "nominal impedance."
Most of the speakers are available in alternative ohm ratings (usually 4, 8 an 16 ohm versions). This variety allows for more flexibility in matching the overall equivalent impedance of your speaker(s) to the output impedance of the amplifier. It is important that the output impedance of your amplifier matches the overall equivalent impedance of your speaker(s) for maximum power transfer and so that you do not damage the amplifier. When using more than one speaker with your amp the equivalent overall impedance changes depending on how the speakers are wired. You can wire multiple speakers "in series," "in parallel" or in a combination of the two wiring configurations ("series/parallel"). Speakers also have a wattage rating which indicates how much power from the amp they can handle before being damaged. When you use multiple speakers, the output power from the amplifier will be distributed among the speakers. I recommend using speakers with the same ohm rating in multi-speaker cabinets so that the power is evenly distributed to each speaker.
Difference between alternating and direct current:
Alternating Current (AC) and Direct Current (DC) are two types of electrical current used in circuits and systems. Here's how they differ:
1. Nature of Flow:
AC (Alternating Current): The flow of electric charge periodically reverses direction. This means the current alternates back and forth.
DC (Direct Current): The flow of electric charge is unidirectional, meaning it flows in one consistent direction.
2. Voltage and Current:
AC: The voltage in AC circuits varies sinusoidally, meaning it rises and falls in a smooth, continuous wave. This creates a corresponding alternating current.
DC: The voltage remains constant over time, creating a steady, unidirectional current.
3. Power Supply:
AC: Commonly used for power distribution because it can be easily transformed to different voltages using transformers, which makes it ideal for long-distance transmission. AC is what's supplied to homes and businesses from the power grid.
DC: Typically found in batteries, solar panels, and electronic devices. Many devices internally convert AC from wall outlets to DC for internal use.
4. Frequency:
AC: Has a specific frequency, typically 50 Hz or 60 Hz depending on the region (e.g., 60 Hz in the United States, 50 Hz in Europe).
DC: Has zero frequency because the current is constant and does not oscillate.
5. Applications:
AC: Used in household appliances, industrial equipment, and large-scale power distribution.
DC: Used in electronics, batteries, solar power systems, and anything requiring a stable, low-voltage power supply.
6. Transmission Efficiency:
AC: More efficient for transmitting electricity over long distances due to the ease of transforming voltage levels.
DC: Historically less efficient for long-distance transmission but has seen improvements with modern high-voltage DC (HVDC) systems.
7. Safety:
AC: Can be more dangerous at high voltages because the alternating nature can cause more severe physiological effects on the human body.
DC: Generally considered safer at lower voltages, although at high voltages, both AC and DC can be dangerous.
Watch the following video to better understand speaker impedance and ohm ratings :
Usefull Equations :
Resistance = Voltage / current
power watts (W) = Voltage x current
power watts (W) = (voltage x voltage) / resistance/impedance
current = voltage / resistance
