Shop Shroud Silencers for Bitcoin Mining

Shroud silencers: a shroud that does acoustic work on the way through

A shroud silencer is a duct shroud with an acoustic element built into the body, so the same part that captures your miner's exhaust also turns a share of its sound back toward the machine instead of letting it ride the air column into the rest of the house. D-Central builds seven of them, and every one works by reactive geometry — a deliberate change in cross-section, and on the v2 bodies a tuned quarter-wave side branch — with no foam, no fibre and no lining of any kind inside the airstream.

That is the whole design position, and it is worth understanding before you choose one. Reactive silencing uses shape. Sound travelling down a duct behaves like a wave in a pipe: meet an abrupt change in cross-sectional area and part of that wave reflects back the way it came. Open the passage out sharply, hold the volume, neck it back down to the collar, and you have an expansion chamber — the same element used in any engine exhaust that has to run near people. Nothing is consumed, nothing needs servicing, and there is nothing to shed downstream into the air crossing your hashboards.

Reactive geometry versus a foam-lined box

The usual product in this niche is a box packed with acoustic foam. Absorptive media does real work, and it also compresses, embrittles in hot exhaust and eventually sheds into the airstream. In a duct that terminates at a hashboard face, that trade reads differently than it does in a recording booth.

These bodies carry no lining at all. Chamber, side branch and collar are shapes cut into one continuous PETG shell, available in black or D-Central orange. The acoustic work is done by the shape of the cavity, so the geometry has to survive as one piece — which is exactly what a single continuous body gives you. There is no seam, no gasket to perish and no fastener to back out at fan frequency.

Which silencer fits which machine

Fitment is decided at the fan face, exactly as it is for the plain shrouds. Every body in this category mounts on the machine's own fan screw positions, and nothing electrical is touched: the stock fans stay, the factory fan curve is unchanged, and the body comes back off with a screwdriver.

Machines with a 140 mm fan pair, the Antminer S21 Pro among them, are served today by the plain S21 Pro dual 140 mm shroud while the dual-140 acoustic body is drawn. Hydro, Hyd and immersion chassis have no fan face and take nothing in this category.

Sizing: the two numbers that decide it

A silencer asks for two things a plain shroud does not: room behind the machine, and a share of the same pressure budget the duct run spends. Both are settled by the footprint row on the listing and the shape of your run.

Collar size — 6-inch or 8-inch

Six inch is 152.4 mm nominal, 8-inch is 203.2 mm, and because area goes with the square of the bore an 8-inch collar carries roughly 1.8 times the cross-section. A chamber and a duct run draw on one budget, so the wider collar is the way to keep an acoustic body from competing with the ducting.

• 6-inch for a short, reasonably straight run: machine near the wall, one bend at most, straight out to a window port. The 6-inch dual 120 mm body is also the shallowest in the range at 152 mm, which makes it the one that still goes in where the big bodies do not.
• 8-inch for a long route, several bends, a shared trunk, or an inline booster doing part of the pull. It is also the right call on a 140 mm machine, which is why the Whatsminer silencer is drawn to an 8-inch collar and not a 6-inch one.

Body envelope — the clearance behind the machine

The reactive bodies span 152 mm to 242 mm across their largest cross-axis. That range is not packaging, it is the acoustic volume doing its job: a chamber has to have a chamber in it, and a quarter-wave branch has to live somewhere. Read the footprint row against the clear space behind and above the machine, including anything racked over it. Where the rack wins the argument, a plain shroud on a longer duct run is the install that goes in.

v1 or v2: broadband chamber, or a tuned side branch

A miner exhaust is not one sound. There is broadband rush from air moving fast, and riding on top of it a tone at the blade-pass region — the rate at which fan blades sweep past a fixed point. The ear locks onto the tone, and it is the tone that carries through a floor and across a property line.

• The v1 expansion chamber treats the spectrum broadly with a single reactive step. Take it when the general rush is what bothers you, and when the flattest possible body is what fits.
• The v2 side branch keeps that chamber and hangs a closed stub off the passage, cut to a quarter of the wavelength being targeted. Sound runs down the stub, reflects off the closed end, rejoins half a wavelength behind itself and cancels around that frequency. It is a textbook side-branch resonator, executed as one printed piece with nothing sitting in the airstream.

The branch is a dead-end pocket beside the flow path, not an obstruction inside it, so the main passage keeps the shape it had on the v1. What changes is the object: the 6-inch v2 measures 250 × 242 × 219 mm against the v1's 250 × 211 × 152 mm. In airflow terms the branch is the cheap part of the design; in shelf space it is not, and clearance decides between them as often as acoustics do.

Where a silencer belongs, and where a plain shroud is the better buy

These are the bodies for a machine that lives where people are: a basement under a bedroom, a garage sharing a wall with the house, a workshop with someone in it all day, a shop with neighbours. That is the case they are drawn for and the case they are worth paying for.

It is also worth saying which install wants the plain part instead. On a machine already sitting at the top of its thermal range, or a duct route that is long and full of bends before it reaches outside, the plain dual 120 mm to 6" duct shroud is the part to buy and routing is the better lever on noise. That is buying advice from a shop that works on these machines, and it is the same advice we would give across a bench.

• Reflects sound energy with reactive geometry rather than absorptive packing
• Carries no lining, so nothing compresses, embrittles or sheds into the duct
• Merges both fan columns into one plenum before the acoustic step on the dual bodies
• Mounts on the stock fan screws — no bracket, no drilling, no wiring, no fan change
• Terminates on the same collar standard as every fitting in the line, so the run downstream is untouched
• Comes out as one continuous PETG shell: chamber, branch and collar in a single piece

Made to order in Montreal, Quebec, and published open source

Each silencer is printed for the order it belongs to and shipped worldwide from Canada. A tuned resonator is the kind of geometry most shops would keep to themselves; D-Central publishes it. Every body in this category is released under CC BY-SA 4.0 at the 3D models download center — download it, retune the stub for your own fan speed, widen the chamber, print it and sell what you make. Acoustics is old, well-documented engineering. The only thing worth owning is the willingness to draw it properly, and D-Central's fund page is what keeps that drawing board busy.

Frequently asked questions