The MULTIFAN S3 is the one most people should buy. A single 120 mm fan at 52 CFM and 18 dBA — double the airflow of the 80 mm S1 for one extra decibel, because a larger fan turns more slowly to move the same air, and speed is what you actually hear. It is 12 cm square and 2.5 cm thick, which still fits under, behind or on top of most AV gear, consoles, modems and amplifiers.
The size that makes the most sense
120 mm is the sweet spot for component cooling. It moves enough air to matter — 52 CFM will keep a receiver or a console out of thermal trouble — while staying small enough to fit the gaps around real equipment. At 1,300 RPM it turns slowly, and slow is quiet.
The comparison worth understanding: the 80 mm S1 spins at 2,000 RPM to produce half this airflow. Whenever the space allows the bigger fan, the bigger fan is the quieter answer.
Built to run for years, not months
Dual ball bearings rated by AC Infinity at 67,000 hours, and the fan mounts horizontally or vertically — sleeve-bearing fans object to one of those orientations and fail early in it. The fans themselves are UL-507 recognised, and the unit is CE and RoHS certified.
The in-line dial has a power switch and sits on the cord, so it ends up somewhere reachable rather than behind the gear. Eight anti-vibration rubber feet come in the box; they matter, because a fan resting directly on a hollow shelf turns the shelf into a soundboard and that is usually what someone is hearing when a quiet fan sounds loud.
Specifications
| Manufacturer | AC Infinity Inc. |
| Product / model | MULTIFAN S3 / AI-MPF120A |
| UPC | 854759004310 |
| Configuration | Single 120 mm fan |
| Dimensions | 12.0 × 12.0 × 2.5 cm (4.7 × 4.7 × 1.0 in) |
| Hole-to-hole spacing | 10.5 × 10.5 cm, Ø0.4 cm screw holes |
| Airflow | 52 CFM |
| Noise | 18 dBA |
| Speed | 1,300 RPM |
| Static pressure | 1 mm-H₂O |
| Operating voltage | 3–7 V DC (USB) |
| Power / current | 1.6 W / 0.32 A |
| Power cord | 1.8 m (6 ft) |
| Controller | In-line multi-speed dial with power switch |
| Daisy-chaining | Pass-through USB port — up to four units on one power source |
| Operating range | 0–70 °C / 35–85% RH |
| Bearings | Dual ball, rated 67,000 hours (manufacturer rating) |
| Mounting | Horizontal or vertical |
| In the box | Fan, in-line speed controller, eight anti-vibration rubber feet, 1.8 m USB cord |
| Certifications | UL (fans) · CE · RoHS |
| Product manual | Download PDF |
FAQ
S3 or S4?
The S4 is 140 mm and moves a little more air — 57 CFM against 52 — at a lower 1,200 RPM. It is the quieter fan for the same job if you have the extra 2 cm in each direction. The S3 wins on fit, and 12 cm goes into far more places than 14 cm does. Measure the gap and let that decide.
One S3, or a dual unit?
One fan is right when the heat is in one place. A dual unit like the S7 earns its place in a closed cabinet, where you want air coming in low and leaving high rather than just circulating. Note the two fans in a dual unit are permanently joined and cannot be run separately.
Where does it plug in?
Any USB port — most people use one on the back of the device being cooled, so the fan powers up and down with it. A USB wall adapter or power bank works too. It runs on 3–7 V DC, so there is no mains wiring and nothing to install.
Can I run several from one port?
Yes. Each unit has a pass-through USB port, so up to four fans can daisy-chain onto one power source — which is how most multi-shelf and rack setups get built.
Will I hear it in a quiet room?
Barely, and only at full speed. 18 dBA is the rated figure at maximum; the dial exists so you can find the point where the gear stays cool and the fan is inaudible, and there is usually plenty of room between those two. The rubber feet do more for perceived noise than most people expect.
Will it pull air through a duct or a filter?
No. At 1 mm-H₂O this is a low-pressure fan for moving air across open components; attach ducting or a filter and the airflow collapses. If the air has to travel through something, use an inline duct fan.
Is this genuine AC Infinity stock with Australian warranty?
Yes. Quick Bloom Lights is the official Australian importer and distributor for AC Infinity. Stock is held in Sydney, orders ship domestically, and the two-year warranty is handled here rather than through an overseas seller.