
It all started in 1820 when Hans Christian Ørsted observed that a current  running through a wire resulted in a deflection of a compass needle.
 André-Marie  Ampère demonstrated that  parallel wires carrying currents attract or repel each other, depending on  whether currents are in the same or in opposite directions.
In 1873 James Clerk Maxwell published a Treatise on  Electricity and Magnetism
He proved  that electricity  and magnetism are the same electromagnetic force.
It took a while before this fundamental research turned in something useful: audio.
There are many fierce debates on the audio forums like
Nobody says all speakers sound the same. Even studio  monitors said to be designed with transparency as the design goal do sound  different.
    Yes all speakers color and probably affect sound quality  more than any other component.
Drivers
    Conventional speakers (moving coil) dominate but there are  other designs.
    
Crossover
    Our audible range is very broad (30-20.000 Hz). This is to  demanding for a single speaker.
    The task is split between a woofer and a tweeter so you need  a crossover.
You  connect the speakers to the amp with a wire. There are alternatives like  bi-wiring, bi-amping and active crossovers.
  
Amplification
    Passive speakers dominate the home, active speakers the  studios.
    
Measurement
    Speaker measurements tells a lot about the characteristics  of a speaker.
    
Placement
    The sound produced by the speakers interact with the room  acoustics.