Look165 wrote:


One works with electromagnetic force, the other works with piezoelectric
force.

The first is low impedance and good for low frequencies,


** The two facts are not related.


The other is high impedance and good for high frequencies, it uses voltage.


** See above.


With a typical 8-Ohm or 32-Ohm output, the crystal headphone is useless.



** Utter nonsense.

In the 1960s, transistor radios and came supplied with crystal earpieces.


..... Phil