Watt and sound output of speaker

Base on the premise that all the conditions are the same, if the drive circuit provides enough voltage, the speaker can generate higher sound pressure level. However, with the same voltage, but we use another speaker which applies higher rated power, it will be difficult to drive and output lower sound pressure level.For example, a circuit can only provide the power of 8 ohm 1 W, in order to generate higher sound pressure level we collocate a 2W speaker, the SPL will be lower instead of higher. It is because with the increasing of the power, the diaphragm should be thickened. The coil also needs to be replaced by thicker wires. However, the thicker wires results in lower impedance so we have to wind a bit longer more, and that makes the coil heavier than before. Oppositely, if we use another speaker which loads lower power or with lower impedance, it is likely to make a little bit higher SPL, however the noise or burning down will possibly happen in this condition.

Magnetic Buzzer and Piezo Buzzer

There are two types of buzzers, piezo and magnetic type.A piezo buzzer generates sound because of the piezoelectric effect from the piezoelectric ceramic which drives the metallic diaphragm to vibrate.

A magnetic buzzer is based on the electromagnetic principle, the metal diaphragm is pulled when input the power, and spring back without power.The piezo buzzer is driven by square waves, and the magnetic buzzer needs 1/2 square waves to drive.

We suggest inputting higher voltage for a piezo buzzer, normally over 9V to have enough SPL. On the other hand, a magnetic buzzer can be driven to generate 85 dB by only 1.5V, but the consumption of the current will be much higher than Piezo one.To compare the two types of buzzers, the magnetic type can have lower frequency response with the same dimension.Though being limited by the dimension, the SPL of a magnetic buzzer can only reach to 90 dB. The piezo buzzer can achieve the SPL of 120 dB in some spec., some larger size can also easily reach to 100 dB.