How many watts should your Bluetooth speaker have?

You might assume that doubling your Bluetooth speaker's wattage will double its loudness, but audio physics and speaker specs don't work that way.

Speaker power can also be measured in two different ways: RMS (root mean square) and peak ratings. Manufacturers and retailers often list only one of these two figures, making it difficult to compare different speakers based on their power rating alone. So how many watts do you actually need in a Bluetooth speaker and what should you look out for when shopping for one? Here's a quick rundown.

ZikG/Shutterstock The peak power rating is easier to understand: it's the maximum electrical power a speaker's amplifier can handle. However, this peak power rating can usually only be sustained for short bursts without causing problems or damaging the speaker's internal components . This is why you'll often see two power ratings on speakers, sometimes with a drastic gap between them. The second power rating you'll commonly see on speakers is an RMS rating. The RMS figure reflects the sustained power that the speaker can actually handle over long periods of time.

It's common for a speaker to boast a peak power rating of 40W while only handling 20W RMS during continuous operation. However, manufacturers rarely disclose the RMS power rating for each model and often opt to publish the maximum power figure instead. This makes the speaker seem more impressive on paper, especially when compared with the RMS ratings of competing speakers.

Brick-and-mortar and online retailers often don't distinguish between the RMS and peak power ratings either. Take the JBL Go 4, for instance. JBL's official spec sheet rates it at 4.2W RMS, but Target doesn't list the power ratings. Some manufacturers don't publish RMS ratings at all, so you might have to look for independent reviews that report real-world testing data.

Even between two accurate RMS figures, though, you can't conclude that a higher rating always results in a better speaker. The actual speaker drivers and their sensitivity play a far more important role. An efficient 10-watt speaker may very well outperform a 20-watt model, so it's best to use power ratings as a starting point rather than a definitive point of comparison.

Nara_money/Shutterstock A speaker's power rating and its loudness aren't linearly related. Doubling the power rating only increases the sound output by approximately 3 dB. Meanwhile, our ears perceive a sound as roughly twice as loud when the volume increases by 10 dB.

Put simply, you only get a 3 dB sound level increase going from 10W to 20W, another 3 dB jump going from 20W to 40W and so on. You need a tenfold jump in power to double the loudness. The difference between a 25W and a 35W speaker is therefore not as significant as you might think.

Finally, keep in mind that even speakers within the same power range can offer drastically different sound profiles and volume levels. It's difficult to gauge a speaker's performance based on the spec sheet, power rating or size alone.