The only advantage the Sonos Sub Gen 3 has over the Gen 2 is its higher processing speed.
Summary
Here's the short answer to Sonos Sub Gen 2 vs Gen 3:
While Sub Gen 3 is an upgrade over Sub Gen 2 in terms of processing speed, you don't need to spend extra for Gen 3 unless you're having wireless connectivity issues at home. Both models are virtually the same product.
...Meaning that they also perform the same in terms of sound quality.
Speaking of which...
ASAP Science made a video on the loudest and quietest rooms in the world. A mind blowing example of the importance of acoustics (time adjusted video).
Other parameters such as the age/materials of the building, the furniture & carpets in place, ceiling height, etc can and will, of course, have an effect on room acoustics, too. But much less.
Anyways...
While Gen 3 is an upgrade over Gen 2 in terms of processing speed, you don't need to spend extra for Gen 3 unless you're having wireless connectivity issues at home. I'd still get the Gen 3 for the peace of mind though.
We get it—you don't want just to hear sound, you want to feel it. What would movies like Earthquake be without Sensurround? And once you've listened to Led Zeppelin's "Moby Dick" or NWA's "Dope Man" with subwoofers, there's no going back to standard full-range speakers.
Sonos, of course, has long been recognized as a premier manufacturer of home audio products but is best known for its high-quality speakers.
The company debuted the Sonos Sub in June 2012; Sonos Sub Gen 3 first appeared on 10 June 2020, replacing the now-discontinued (albeit still supported) Gen 2 model, released in 2016.
Like all Sonos speakers, the Sub requires a WiFi connection to function. It also must be plugged into a working AC power outlet.
Other than these prerequisites, the Sub can be placed anywhere—under a sofa or table or against a wall. It sounds the same, either standing up or lying down flat.
Meet the New Boss—Same as the Old Boss
Are there tangible differences between Sonos Gen 2 and Gen 3? Not many—the biggest difference between the two is the price.
Both have the same shape—a square-shaped alphabetical "O"—and share most of the same specs.
Both are about the size of a large wedding cake box and weigh 16 kg (33.8 lbs). Available in either black or white gloss, they come equipped with a 10/100 Ethernet port, two Class-D digital amplifiers and two force-canceling drivers. Frequency response is rated as low as 25 Hz; the lowest pitch most people can hear is 20 Hz.
The other available color for the Sub is black.
In fairness, Sonos Gen 3 offers more than just a higher price point. Its random access memory (RAM) doubles that of Gen 2 (258 MB to 126 MB). Gen 3's radio receiver is also more powerful, offering better range and more consistent connectivity.
And Sonos updated Gen 3's CPU to 1 GHz for faster processing speed. The idea is to make Gen 3 "future-proof" for subsequent firmware updates.
Other minor improvements for the Sonos Gen 3 include a now-rounded pair button. It's inset into the cabinet for a more ergonomic, streamlined look. The redesigned flatform power cord minimizes any potential snarls with adjacent cabling. Moreover, it works with any Sonos speaker or home cinema model save for the Sonos Move.
Check here the User Guide for Sonos Sub.
Remember the S2 App
While both Sonos Gen 2 and Gen 3 are wireless-capable, the Gen 3 may be the subwoofer you need if you're experiencing wireless connectivity issues with previous Sub models.
Sonos Gen 3 comes equipped with Bluetooth Low Energy (BLE) and Near-field Communication (NFC) options for easy 1-button pairing. Both require the Sonos S2 App for initial set-up. The S2 control platform also engages sound volume levels and content searches.
Both Sonos Gen 2 and Gen 3 deliver a seismic sound that resonates the marrow in your bones, yet is clean and distortion-free. Even those with "golden ears" won't discern any sonic differences between the two models. According to a Sonos user board, Gen 3 supposedly has less vibration compared to its predecessors but again the difference is negligible.
The Verdict
If you loved the Sonos Gen 2, you'll be enthralled with Gen 3 (except for its higher price). Sonos didn't try to "reinvent the wheel" with Gen 3; it retains the innovative design (its face-to-face force-canceling drivers) that eliminates any buzz or oscillation yet delivers unbelievably powerful and dynamic low-end sound.
It also retains a sleek, futuristic look but functions just as well if tucked away under furniture (note: enclosing it in a cabinet will reduce its sonic impacts and data streaming speeds).
So, if your current Sonos Gen 2 performs to your satisfaction (e.g., no data streaming issues), there's no need to upgrade to Gen 3. Alas, the Sonos Sub only pairs with other Sonos amplified components.
Also, the Trueplay feature (used to "measure how sound reflects off surfaces in a room, then fine tunes your Sonos speaker to make sure it sounds great no matter where you've placed it") only works with iOS.
Android users, take note.
Sonos Gen 2 models are available for sale on Amazon and Newegg at a considerable discount compared to Gen 3. Since Sonos still supports the original Gen 1, one can confidently presume that the company will continue Gen 2 well into the future.
If you've already optimized your home for streaming devices (i.e., a WiFi network divided into 2.4 GHz and 5 GHz), most likely Gen 2 will suffice for your use.
Trust us, you've never been immersed in surround sound like what you'll hear with the Sonos Sub. While it may not rank with the Conversion of the Apostle Paul, you'll still experience an epiphany of auditory sensation like never before.
Lastly, here's a good video compares the two: