Speakers should have a much wider range of output frequencies than simple buzzers.
To check this, add a buzzer to your circuit; e.g. add the + lead of a buzzer to GPIO
pin 5. For example, a buzzer might have trouble producing much sound at a frequency
less than 50Hz, or greater than 3000 Hz.
Use the makesound() function to make a
very low frequency sound first from the buzzer, and then from the speaker. Try the
same with a high frequency sound.