[John Williamson]

On 22/04/2019 08:03, Don Pearce wrote:

Particularly with pink noise, they have no choice but to apply a
voltage - which is what amplifiers generate. The actual amount of
power that results in is something the speaker has to negotiate with a
deity, cos it certainly isn't negotiable with any human.

When they talk about 1 watt, they are just assuming a nominal
impedance, which for any particular driver over an extended bandwidth
is a fiction.

Electrically...

True RMS current meters are cheaply available,as long as you stick to
audio frequencies. RF ones cost a bit more....

One that I use doesn't even need to be electrically connected to the
unit, as it uses a hall effect sensor to check the current in one of
the speaker wires. It works over the whole audio range.

That and a decent voltmeter along with a sweep tone generator can be
used to draw a graph of impedance against frequency, though to be
accurate, you need to use an oscilloscope t and a couple of low value
resistors in the circuit to detect any frequency dependent phase shifts
in the load, or use a hall effect sensor to generate a voltage to drive
the X plates on the 'scope. If you have a DAW, then you have a way to
generate a sine or pink tone good enough for the job, even using a free
DAW program such as Audacity.

The only reasons the makers don't do it, as far as I can tell, are that
it is time consuming, there is a lot of variation between speakers as
they come off the line, and then there is the problem of getting an
accurate enough microphone to check the physical response.


--
Tciao for Now!

John.