I'm exploring radio receiver circuits, and on my workbench I have an audio amp, 9v, designed for 8ohm load.
I'm not getting acceptable volume at 8ohms, so I tried a 4" 32ohm speaker, and it was much better for
my ears, which seems odd, as I would expect more volume with a lower impedance unit. Why that is, i don't know. Maybe
it was because they were little 8Ω/50mm units, without and enclosure.



Also, I am contemplating making my own diy headphones from hearing protection muffs, using different driven
elements. I have some 150ohm telephone speakers, 2" 100ohm speakers, and various piezo elements. As for the speakers,
my thinking was to connect them in series, and see how it sounds. However, for the piezo elements, and tiny piezo horns that I have,
I'm not sure of the added circuitry, maybe a capacitor in series?. I know the enthusiasts for crystal radio designs will use piezo elements, but as I recall, no added circuitry is needed, as piezo is already "hi-z".

 

Why that is, i don't know.

If your 9V supply was a PP3 battery, it might not have been able to provide enough current to drive the 8 Ohm speaker adequately.

 

Yeah, that is what I was thinking. I tried with eight AA cells in series, same weak audio, however, I've yet to try this small 50mm speakers in an enclosure.