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The short answer: both the Sub Mini ($429) and the Sub 4 ($799) are rated down to 25Hz — and that shared number is the most misleading spec on either product page. The Sub 4 moves dramatically more air: dual 5×8″ elliptical woofers in a ported cabinet versus the Mini’s dual 6″ sealed drivers. In a small-to-medium room at sane volumes, the Mini gives you most of the experience for half the money. In a large room, or if you ever want two subs, the Sub 4 is the only correct answer — because the Mini is a dead end for dual-sub setups, and you can’t add a Mini to a Sub 4 later. Choose accordingly, once.
This is the buying logic no spec sheet or retailer will give you: what “25Hz” hides, the room-size breakpoints, the dual-sub rules that affect your upgrade path for years, the used Sub Gen 3 play, and the legitimate case for buying neither.
We haven’t measured either sub in a room. Specs below are from Sonos’s published documentation; the 25Hz discussion is based on how subwoofer specifications work plus independently reported estimates (attributed, not our measurements). Owner experiences are paraphrased from community discussions.
The 25Hz paradox: what the spec doesn’t tell you
Sonos rates both subwoofers as playing “down to 25Hz.” Read quickly, they look identical on bass extension. They’re not, and understanding why will make you immune to a whole category of misleading spec comparisons.
A frequency-response number without a loudness qualifier is incomplete. “25Hz” tells you the sub produces something at 25Hz — it doesn’t tell you how loud that something is relative to the rest of the output. The industry convention is to state the dB down-point (e.g., “25Hz at -3dB”), and Sonos doesn’t publish one for either product. Independently reported estimates put the Sub 4 around -6dB at 25Hz and the Sub Mini closer to -10dB — meaning the Mini’s 25Hz output is substantially quieter relative to its mid-bass. Those are estimates, not Sonos-published figures, but the physics is unambiguous: the Sub 4’s far larger driver area and ported cabinet move much more air at the bottom octave.
The practical translation:
- Sub Mini at 25Hz: it’s there — you can feel low rumble in small rooms — but it’s the sub working at its limit. This is a 30Hz-and-up sub in real-world terms.
- Sub 4 at 25Hz: it’s there with authority. Explosions, pipe organs, and cinematic LFE have weight the Mini can’t produce.
- Above ~40Hz (kick drums, bass guitar, most music): the gap narrows enormously. This is where the Mini earns its “most of the experience” reputation — music bass lives here, and the Mini is excellent at it.
So the spec-sheet tie breaks like this: for movies in big rooms, the Sub 4’s extension advantage is real and audible. For music and TV in normal rooms, you’re paying double mostly for headroom you’ll rarely use.
Sub Mini: who it’s for
- Dual 6″ force-canceling woofers (facing each other to cancel vibration), sealed cabinet, 14 lb / 6.35 kg, 12″ tall cylinder in matte black or white
- WiFi 2.4/5GHz, Ethernet port, NFC tap-to-setup, Trueplay tuning
- Pairs with Beam, Ray, Era 100, One/One SL, Arc family — basically any amplified non-portable Sonos product
The Mini is the natural match for the Beam (any generation), the Ray, and Era-based systems. Its cylindrical shape tucks beside furniture in a way the big square Sub never will, and at 14 pounds you can move it around to find the best spot — subwoofer placement matters more than subwoofer choice, and the Mini is the one you’ll actually bother to position properly. For apartments and small-to-medium rooms, it’s the value king of the Sonos lineup, and the community’s “most of the bass for half the price” wisdom is, with the caveats above, roughly right.
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Sub 4: who it’s for
- Dual 5×8″ elliptical force-canceling woofers, ported cabinet, matte finish, substantially larger and heavier than the Mini
- WiFi 6, faster processor and more memory than the Gen 3, lower idle power — the acoustic signature is essentially the Sub Gen 3’s, the upgrades are in efficiency and future-proofing
- The intended partner for the Arc Ultra and large-room Arc systems
The Sub 4 is for rooms where the Mini runs out of breath: large open-plan living areas, dedicated media rooms, and anyone who listens loud. It’s also the only sub in the lineup that keeps the dual-sub door open (see below). If your room is over ~300 sq ft or your seating is far from the sub’s likely position, the Mini’s output advantage evaporates with distance — bass falls off fast, and headroom is what you’re buying.
Room size × volume: the decision table
| Room | Listening level | Buy |
|---|---|---|
| Apartment / bedroom / small living room | Moderate | Sub Mini — the Sub 4 is money you’ll never hear |
| Medium living room (~150–300 sq ft) | Moderate | Sub Mini — the sweet spot |
| Medium living room | Loud / movie nights matter | Sub 4 — headroom you’ll use |
| Large / open-plan (300+ sq ft) | Any | Sub 4 — the Mini can’t pressurize the space |
| Any room | “I might add a second sub someday” | Sub 4 — the Mini can’t do dual-sub, full stop |
When in doubt, the tiebreaker is distance: bass output drops rapidly as you move away from the sub. If your couch is 12+ feet from where the sub will sit, lean Sub 4. If it’s 6–8 feet, the Mini is plenty. Our system planning guide and the System Builder tool can help you map the whole system at once.
Dual-sub rules: the future-proofing section
This is the least-understood part of the Sonos sub lineup, and it should influence your purchase today:
- Two full-size Subs (Gen 3 or 4) in one home theater: supported. At least one should be a Gen 3 or newer (the processing requirement); the second can be an older full-size Sub.
- Two Sub Minis in one home theater: NOT supported. Confirmed by Sonos’s own customer care — the Mini is single-sub only.
- One Sub Mini + one full-size Sub: NOT supported. You can’t mix them in the same room.
- The upgrade path is replacement, not addition. If you buy a Mini now and later want more bass, you sell/replace the Mini — you can’t add a second Mini or a Sub 4 alongside it.
This is the Sub 4’s hidden value proposition: it’s the only sub that leaves every door open. If there’s any chance you’ll end up in a bigger room, or catch the home-theater upgrade bug, the Sub 4 is the cheaper long-term buy despite costing double today. The compatibility matrix has the full pairing rules.
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Sub Gen 3: the used/refurb play
The Sub 4 replaced the Sub Gen 3 with what amounts to the same acoustic design plus WiFi 6, a faster chip, and lower idle power. Sonos didn’t change the sound. That makes used and refurbished Gen 3 units — including Sonos’s own certified refurbished stock — the value sleeper of the lineup: full-size output, dual-sub eligible, at a meaningful discount to the Sub 4.
Caveats: no WiFi 6 (irrelevant for most networks today, possibly relevant in five years), higher idle power, and buying used means checking the warranty situation. But if you find a certified refurbished Gen 3 at a real discount, it’s sonically a Sub 4 for less money. Our Sub Gen 3 page has the details.
Do you even need a sub?
The trust section. Not everyone does:
- Arc Ultra owners: the Arc Ultra’s Sound Motion bass is the best low-end any Sonos soundbar has produced alone. In a small-to-medium room, try the bar solo for a week before buying a sub — a meaningful fraction of owners stop there.
- Apartment dwellers: a subwoofer you can’t turn up is furniture. If your walls are thin and your lease is strict, the money is better spent on surrounds — see our Era surrounds guide and the apartments guide.
- Music-first listeners: the Era 300s and even the Beam Gen 2 produce respectable bass for music. A sub helps, but it’s the smallest upgrade per dollar in a music-first system — surrounds or a better bar come first.
- Movie-first, medium+ room: yes, you need the sub. This is the purchase the system was designed around. No soundbar, however good, moves air like a dedicated woofer.
Setup basics
Placement matters more than which sub you bought: corners reinforce bass (often too much — try it before committing), mid-wall placement is usually flatter, and the sub doesn’t need to be near the soundbar — anywhere in the room works, near an outlet. Run Trueplay after placing it (the sub is included in the tuning), then adjust the sub level in the app to taste — owners consistently report Sonos’s default is slightly hot for music and about right for movies. Give it a week before judging: your ears recalibrate to proper bass faster than you’d expect.
Disclosure: As an Amazon Associate, we earn from qualifying purchases. Prices checked October 2026 — verify current pricing before buying. The 25Hz dB-point figures are independently reported estimates, not Sonos-published specifications.
