How to check Ohms of speaker simply?

hypothetically you could make a pair of high-z magnetic headphones with tin can lids and small 2k to 10k audio transformers with E-I cores (the cores need to be disassembled, and then reassembled with just the E parts). you can get a basic idea how the old high-z headphones were constructed on this page, which has some good pix of the internal parts http://oldheadphones.com/crystal/info/restore.html

don't use aluminum for the diaphragm, it must be a magnetic metal.

somehow i'm thinking there's a magnet in the assembly somewhere.... i've taken a pair of high z phones apart before, and i seem to remember a magnetized ring under the diaphragm rim... long time ago before high school

NIL,

or you could use a simple audio amp with a commonly available lo-z headphone as shown here.

MikeMl said:

NIL,

or you could use a simple audio amp with a commonly available lo-z headphone as shown here.

Click to expand...

Page has been stolen from Charles Wenzel's page from here - http://www.techlib.com/electronics/crystal.html

Ok, if I cannot find any hi z earphone, then my first alternative will TL431.

If you need an audio power amplifier then why not use one like a simple LM386?
It is stupid to use an TL431 voltage regulator instead of an audio power amplifier.

Willen said:

Ok, if I cannot find any hi z earphone, then my first alternative will TL431.

Click to expand...

You could use lower impedance headphones with a matching transformer:

https://www.crystalradio.net/soundpowered/matching/

https://www.peeblesoriginals.com/catalog/72.php

A matching transformer reduces the output level then it might be so low that it can barely be heard.

I have never made a simple crystal radio but most articles say with high impedance headphones a strong local station is not very loud.