Z=R+jX is measured with Ohms

Where

Z is impedance measured with Ohms

R is resistance measured with Ohms -- a constant value that does not depend on freequency.

X is reactance measured with Ohms -- freequency depended.

j is directional vector on the complex plane hence the value is complex(lookup a complex arithmetics to understand further)

X = Xl + Xc

Where

Xl is product of inductance with angular freequency i.e. inductive reactance that ideally is taken as short circuit in DC and goes higher with higher freequencies.

Xc is a reversed product of capacitance with angular freequency i.e. capacitive reactance that is ideally taken as open circuit @DC and decreases its value as the freequency increases.

Impedance can also be defined with Ohm's law but with more variables such as freequency and phase.

A TRIVIAL EXAMPLE:

Can you try to start the car with 10 AA 1.5V batteries connected in-series with each other?

The answer is obviousely NO.

The internal resistance of 10 AA batteries is substantially high and adds on to the small internal resistance of the car starter thus giving a very small resulting current that isn't enough to rotate the motor.

The solution is to have a battery source with matching resistance to a car starter.

The same thing you should consider in audio applications with IMPEDANCE, the complex value explained above.

Further:

Lookup at thesaurus in the Microsoft Word for "imped" to get an array of synonims and one of them is "hold up".

Where

Z is impedance measured with Ohms

R is resistance measured with Ohms -- a constant value that does not depend on freequency.

X is reactance measured with Ohms -- freequency depended.

j is directional vector on the complex plane hence the value is complex(lookup a complex arithmetics to understand further)

X = Xl + Xc

Where

Xl is product of inductance with angular freequency i.e. inductive reactance that ideally is taken as short circuit in DC and goes higher with higher freequencies.

Xc is a reversed product of capacitance with angular freequency i.e. capacitive reactance that is ideally taken as open circuit @DC and decreases its value as the freequency increases.

Impedance can also be defined with Ohm's law but with more variables such as freequency and phase.

A TRIVIAL EXAMPLE:

Can you try to start the car with 10 AA 1.5V batteries connected in-series with each other?

The answer is obviousely NO.

The internal resistance of 10 AA batteries is substantially high and adds on to the small internal resistance of the car starter thus giving a very small resulting current that isn't enough to rotate the motor.

The solution is to have a battery source with matching resistance to a car starter.

The same thing you should consider in audio applications with IMPEDANCE, the complex value explained above.

Further:

Lookup at thesaurus in the Microsoft Word for "imped" to get an array of synonims and one of them is "hold up".