More wattage doesn't always mean a louder Bluetooth speaker. Audio physics and speaker specs don't work that way, so doubling a speaker's wattage won't double its loudness.
Wattage may seem like an easy way to compare Bluetooth speakers, but it's not the most straightforward measure of quality or volume. Speaker power is measured in two ways: RMS (root mean square) and peak ratings. Manufacturers often list only one figure, making comparisons difficult. The peak power rating is the maximum electrical power a speaker's amplifier can handle, but it can only be sustained for short bursts. The RMS figure reflects sustained power over long periods.
Doubling the power rating only increases sound output by approximately 3 dB, not a doubling of loudness. A tenfold jump in power is needed to double the perceived loudness. An efficient 10-watt speaker may outperform a 20-watt model. Power ratings should be used as a starting point, not a definitive comparison.
Even speakers within the same power range can offer drastically different sound profiles and volume levels. It's difficult to gauge performance based on the spec sheet, power rating, or size alone. Speaker drivers and their sensitivity play a far more important role than wattage.
Source: Engadget · Summarized by HeadlinesBriefing