The MULTIFAN S4 is the largest single fan in the range at 140 mm, and the quietest way to move this much air. 57 CFM at 18 dBA — but the number that explains it is 1,200 RPM, the slowest in the range. A bigger blade turning more slowly moves more air with less noise, which is why the S4 is the one to choose whenever you have the 14 cm of space for it.
Bigger blade, lower speed, less noise
It is worth understanding why the largest fan is also the calmest one. Airflow depends on blade area and speed; noise depends overwhelmingly on speed. Increase the area and you can drop the speed while moving the same air — or more of it.
The range shows this cleanly. The 80 mm S1 spins at 2,000 RPM for 26 CFM. The 120 mm S3 spins at 1,300 RPM for 52 CFM. The S4 spins at 1,200 RPM for 57 CFM. More air, less rotation, every step up.
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 S4 / AI-MPF140A |
| UPC | 854759004365 |
| Configuration | Single 140 mm fan |
| Dimensions | 14.0 × 14.0 × 2.5 cm (5.5 × 5.5 × 1.0 in) |
| Hole-to-hole spacing | 12.5 × 12.5 cm, Ø0.4 cm screw holes |
| Airflow | 57 CFM |
| Noise | 18 dBA |
| Speed | 1,200 RPM |
| Static pressure | 0.84 mm-H₂O |
| Operating voltage | 3–7 V DC (USB) |
| Power / current | 1.5 W / 0.3 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
S4 or S3 — is 5 CFM worth the extra size?
The airflow gap is small; the reason to take the S4 is that it delivers it at 1,200 RPM instead of 1,300, so it is the calmer fan in a room you sit in. If the space is tight, take the S3 without hesitation — 12 cm fits a great many places 14 cm does not, and the difference in performance is marginal.
Will it fit my cabinet or shelf?
It is 14.0 × 14.0 cm and 2.5 cm thick. The thickness is rarely the problem; the footprint sometimes is. Measure the flat area you intend to stand it on or the gap you want to slide it into before ordering — this is the one model where fit is the deciding factor rather than performance.
Why is its static pressure lower than the smaller fans?
Because it turns more slowly. At 0.84 mm-H₂O it is the lowest in the range, which is fine for its job — moving air across open components — but it is another reason none of these fans suit ducting or filters. If air has to be pushed through something, use an inline duct fan.
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.
Should it blow at the device or pull air away?
Pull away, usually. Heat rises and collects, so extracting from the hottest point and letting cooler room air flow in behind it works better than blowing at a hot casing. In a closed cabinet you want both, which is what a dual unit like the S7 is for.
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.