7. How to decide micro-speaker specifications?
First, clients should decide based on their input power source. For 3.3V power source (achieved by step-down transforming battery source as in cellphones), clients usually choose 4 ohm or 8 ohm micro-speakers. For 4 ohm speakers, input power is commonly 0.5W; for 8 ohm speakers, input power is commonly 1.0W. For 5.0V power source (as sources provided by USB), clients usually choose 4 ohm speakers with input power of 1.5W, or 8 ohm speakers with input power of 2W.
Considering speaker sizes, all else equal, the larger the size, the better the sound performance is. Clients are advised to avoid non-round micro-speakers. Since sound waves are typically spherical, non-round speakers may create two resonant frequencies, one in the middle, and the other created by the non-round silhouette. This could prevent the frequency response from being flat. However, in scenarios in which mechanical design limits the shape of the speaker, clients may choose oval or rectangle speakers, in order to maximize SPL. This is common in PC, cellphone, monitor or TV applications.
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