[Vintage-Audio] Re Crossover and Speaker Impedence

[Roy Morgan]

At 10:14 PM 3/17/2004 -0500, Duane Fischer, W8DBF wrote:
>A speaker cabinet contains three speakers rated at 8 Ohms 
>each,  electronic crossover network.  Is the overall impedence of the system
>affected in any way?

Yes.

A thorough description of how the impedance might be affected would fill a 
thick book.  The design of the crossover network, the characteristics of 
each driver, the nature of the box, and even where in the room the speakers 
are located will affect the input impedance of the system.

The impedance will vary over frequency and will be composed of both a 
resistance and a reactance component.  The variation with frequency would 
astound you.  The overall impedance of a speaker nominally rated at 8 ohms 
may vary from 2 ohms to 40 ohms over the audio range.

A very good instrument to measure such impedances over frequency is an RLC 
bridge, or better yet the Y-Z bridge once made by General Radio.

Roy