Well, obviously 4 ohms isn't 1000 ohms and open circuit at DC, so yes, the new one is clearly not a piezo.
How about you show us a picture of them all? {Remember: perfectly focused and resolution no greater than 1024 by 768.}
I would have preferred if you had kept this in the previous thread.
And - just how did you wire them up? All in parallel I gather?
Apparently that H-bridge driver can't handle 2 ohms - which is not surprising.
The 4 ohm horns need to be connected in series to make 8 ohms - if the H-bridge can't handle them, you will need the LM386 after all.