Not an E.E., so please bear with me a bit.
Have a 2" dia speaker in kid's toy.
Seem like it doesn't work, but hard to get to, to verify.
It says 8 ohms.
I imagine that this is the Z, and not the dc resistance; correct ?
a. What might be a "typical" dc resistance for a
really small (2") speaker like this ?
b. Can't get a really good look at it, as it is really embedded.
It might be more of an electrostatic type of speaker, than the typical
moving coil type.
How would your answers for (a) change, if this is so ?
Even though I could not understand the OP, I do understand that you are
WRONG! Ideally, the speaker voice coil would have a resistance of ZERO.
Unfortunately, it is impossible to manufacture such voice coils short of
having superconductivity. The impedance of the voice coil is ideally
found by applying am ac signal voltage V, measuring the resulting
current flow I and finding the impedance Z = V/I using complex numbers.
The applied V is countered by a back emf so that Z is not equal to the
measured resistance of the voice coil.
I've measured speakers before and yes, an 8 ohm speaker I measured was an
ohm or two. In this case I doubt they'd invest much copper in a speaker
for a cheap child's toy so I'd guess that one would probably read higher.
(Piezoelectric tweeters ohm out as infinite, however)
With an ohmmeter--yes. But suppose you use an ac bridge. A typical
bridge can usually be driven by an external generator as well as an
internal generator usually at 1 kHz. An HP 200A or one of its
descendants is typical.
At low frequencies, the equivalent circuit of the crystal or film will
look like a capacitor in parallel with a resistor. As frequency
increases, the resistance drops from infinity. The capacitive reactance
also drops. As the mechanical resonant frequency is approached, the
reactance drops until it (ideally) reaches zero at resonance.
Probably about 3/4 - 7/8th of the impedance.
For a higher power speaker, the resistance will be
A passive electrostatic speaker is capacitive, but they are
normally used for higher frequences only, together with a
coil speaker for the lower frequencies.
If it says 8 ohms on it,it is most likely just a cheap speaker you could
get at rat shack in several diameters.
Not sure what you mean by "Seem like it doesn't work "
Does sound come out of it or not?
The speaker is not the only thing responsible for the sound.
It's also down on the list of failures on such products.