This year, befitting its Echo speakers' primary function as purveyors of music, Amazon is releasing a whole bunch of new audio gear. The lineup includes a beefed-up Echo Plus speaker, an Alexa amp, a strange pre-amp... thing, a Dot without the speaker and more. But if you already own an Echo and want to get better sound out of it, the new Echo Sub is the most intriguing.

At $130 (£120, AU$199) the Amazon Echo Sub sits between the Echo and Echo Plus in price, and it upgrades the sound of Amazon's smart, skinny towers with actual deep bass. Is it an essential upgrade to the Echo line? No, but if you've ever been frustrated by the Echo's lack of sonic heft, it could be for you. 

The Sub is also available as part of an bundle with two second-gen Echo devices for $250 (£240), which is a viable system for only a little more money than a single Sonos One. I tested the Sub mainly with the Echo Plus, however, and that combo makes less financial sense due to the added cost of the Plus' onboard hub.

View full gallery

Once out of the packaging, the Echo Sub looks like someone left an Echo-shaped sponge in water overnight. It's a cloth-covered pill box with a matte plastic top and it measures 8 inches high and 8.3 inches in diameter (20.2 by 21 cm). The subwoofer is sealed and down-firing, powered by a 100-watt amplifier pushing a 6-inch woofer. The speaker is rated from 200 Hz down to 30Hz (-6dB), with the Alexa app handling the crossover, depending on which device you pair it with.

At the moment the Sub is only officially compatible with the second-generation Echo and Echo Plus, but according to Amazon it will be compatible with most Echo products, as described below. I tried to pair the Sub with a third-gen Echo Dot and it failed, but other Echo devices I tried worked well. I've reached out to Amazon for clarification. 

Smart speaker	Sub pair	Stereo pair
Echo (1st Generation)	x
Echo (2nd Generation)	x	x
Echo Dot (3rd Generation)	x	x
Echo Plus (1st Generation)	x	x
Echo Plus (2nd Generation)	x	x
Echo Show (1st Generation)	x (music only)
Echo Show (2nd Generation)	x (music only)

There's only one input -- the internet (via 802.11 a/b/g/n Wi-Fi) -- and a single button for initiating setup on the back. A separate audio input on the back (like the one found on a Dot) would make the speaker more useful, but without a crossover or volume control you can see why Amazon didn't: keep it simple, subwoofer.

Setup is designed to be as simple as possible, but I had issues at first. I eventually figured out that if you've already set up a stereo pair of Echos and want to add the Sub, you have to start from scratch. After that it worked fine, and setting up the stereo pair itself was simple too.