"Ron Johnson"

If you only had two passive speakers, no sound would come out! You could
save a lot of money on the amplifiers mind

** Ha, ha.

The passive radiator is a way of lowering the tuning of the cabinet whist
keeping a small volume (hence size) and without resorting to bass ports

** A passive radiator is simply another form of tuned port - instead of
the moving mass being simply the air enclosed by the tube, the cone of the
radiator acts as the moving mass. The spring is always provided by the air
trapped in the box.

The main advantage is that it allows small cabinets to be tuned to low
frequencies and with a large moving surface area.

In such cases, a similar frequency air only port would be inconveniently
long and have a too small a surface area - the result of which is a high
level of chuffing noise and strong third harmonic generation.

As with an air only port, the cone motion of a radiator supports the output
of the cabinet in the lowest octave and will be the main source of sound at
box resonance.


.... Phil