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If you own a Sonos soundbar, the Sub 4 is the full-size wireless subwoofer designed to go with it. It replaced the long-running Sub (Gen 3) and keeps the same basic idea: two drivers facing each other inside a slim, furniture-friendly cabinet. Here’s what changed, how it fits into a Sonos system, and when the smaller Sub Mini or a different approach makes more sense.
Sonos Sub 4
The easiest way to add real bass to a Sonos Arc, Arc Ultra, Beam or Ray. It’s wireless, slim and tunes itself with Trueplay. You pay a premium for that convenience, and it only works with Sonos.
- Two 5 × 8-inch elliptical woofers, force-cancelling
- Two Class D amplifiers
- Down to 25 Hz (Sonos spec)
- Wi-Fi 6 and Ethernet
- Stands upright or lies flat under a sofa
If you’re building a Sonos home theater, this is the sub to get, and it’s a clear step up from the Sub Mini in bigger rooms. If you don’t use Sonos, or you want the most bass for your money, a conventional wired sub with a receiver goes further.
- Wireless setup in a few minutes from the Sonos app
- Opposed drivers keep cabinet buzz and rattles low
- Slim enough to lie flat under a sofa
- Trueplay room tuning, now with Wi-Fi 6 and lower idle power
- Works only with Sonos products
- Expensive for the output compared with wired subs
- No wired input, phase control or detailed EQ
Key specifications
| Spec | Sonos Sub 4 |
|---|---|
| Drivers | Two 5 × 8-inch elliptical woofers, facing each other (force-cancelling) |
| Amplification | Two Class D digital amplifiers |
| Enclosure | Ported |
| Low-frequency extension | Down to 25 Hz (Sonos spec) |
| Connectivity | Wi-Fi 6 (802.11ax), 10/100 Ethernet |
| Tuning | Automatic EQ matching with paired speakers; Trueplay room tuning; bass, treble and loudness in the app |
| Works with | Arc Ultra, Arc, Beam (Gen 1 and 2), Ray, Five, Era 300, Era 100 |
| Size and weight | 15.31 × 15.83 × 6.22 in (H × W × D), 26 lb |
| Finishes | Matte black or matte white |
What changed from the Sub (Gen 3)
Acoustically, the Sub 4 follows the Gen 3 closely: the same force-cancelling layout, the same slim footprint and the same 25 Hz rating. The changes are inside and in the details. Sonos lists a faster quad-core processor, more memory, a Wi-Fi 6 radio and up to 50% lower idle power use, plus a new matte finish. It’s also lighter than the Gen 3, at about 26 lb, which makes it easier to move or slide under a sofa.
Reviewers found little audible difference between the two, so a Gen 3 owner has little reason to upgrade for sound alone. Our Sonos Sub (Gen 3) review covers whether a discounted or refurbished Gen 3 still makes sense.
How it sounds
Movies and games
This is the Sub 4’s main job. Paired with an Arc or Arc Ultra, it takes over the deep bass the soundbar can’t reproduce, which also frees the bar to play cleaner and louder. Published reviews describe strong, clean bass with very little distortion, even near the top of its level range, and recommend running Trueplay to blend it with the bar. The opposed-driver design also keeps cabinet vibration low. One reviewer pointed out that the Arc Ultra already has a fair amount of bass on its own, so the Sub 4 matters most if you want more low end or have a larger room. One Sub 4 is plenty for most medium-sized living rooms. In large or open-plan spaces, Sonos supports a second sub with Arc Ultra, and that’s the better route than turning one up hard.
Music
Because Sonos matches the sub’s EQ to the speakers it’s paired with, music tends to sound balanced rather than bass-heavy, and the low end of a Five or Era 300 pair gains real weight. You can’t adjust phase or crossover yourself, so if the blend isn’t right, your tools are placement, Trueplay and the app’s bass slider.
Setup tips
- Run Trueplay after placing it. Every time you move the sub, re-run Trueplay so the system can retune for the new position.
- Try it at the front first. Near the soundbar is the safest starting point. If the bass sounds boomy, move it a little away from the corner; our soundbar sub placement guide explains why.
- Lying flat is fine. The Sub 4 is designed to work on its side, so under a sofa is a valid spot. Leave a little space so the ports aren’t blocked.
- Keep the level sensible. The app’s Sub level control is easy to over-do. Set it so you notice the bass when the sub is switched off, not all the time.
How it compares
| Sonos Sub 4 | Sonos Sub (Gen 3) | Sonos Sub Mini | |
|---|---|---|---|
| Drivers | Two 5 × 8-inch, opposed | Two, opposed | Two 6-inch, opposed |
| Cabinet | Slim, upright or flat | Slim, upright or flat | Small cylinder |
| Rated extension | 25 Hz | 25 Hz | 25 Hz |
| Wi-Fi | Wi-Fi 6 | Older Wi-Fi | Wi-Fi |
| Best for | Arc, Arc Ultra and larger rooms | Discount or refurbished buyers | Beam, Ray and small rooms |
For a Beam or Ray in a small room, the Sonos Sub Mini is the cheaper match and is easier to hide. With an Arc or Arc Ultra, or in a larger living room, the Sub 4 is the better fit. If you aren’t committed to Sonos, a soundbar or receiver with a wired sub output opens up far more choice for the money; see our best subwoofers for Sonos guide and soundbar subwoofer guide.
Who should buy it
- Sonos Arc, Arc Ultra or Beam owners who want proper home theater bass.
- Anyone who values wireless setup and a tidy, low-profile sub.
- Apartment dwellers who want low vibration and the option to hide the sub under a sofa.
- Sonos music listeners with a Five or Era 300 pair.
Who should look elsewhere
- If you don’t use Sonos, it won’t work with your system at all.
- If you have a Ray or Beam in a small room, the Sub Mini is better value.
- If you want the most bass for your money with a receiver, look at our home theater subwoofers.
FAQs
Is the Sub 4 louder than the Sub (Gen 3)?
Sonos hasn’t claimed more output. The acoustic design and 25 Hz rating are the same; the changes are mostly in processing, Wi-Fi, power use and weight.
Can I use the Sub 4 with a non-Sonos soundbar or receiver?
No. It has no wired input and only pairs with Sonos products. For other systems, see our wireless subwoofer guide.
Sub 4 or Sub Mini?
The Sub Mini suits a Beam or Ray in a small room. With an Arc or Arc Ultra, or a larger room, the Sub 4 has noticeably more headroom.
Can I use two Sub 4s?
Yes, with Arc Ultra Sonos supports a second sub for more even bass across a room. Our dual subwoofer guide explains the benefit.