Approval request

Strain relief for the Crestron box audio output

A printed box that protects the audio connection on every unit, so a pulled cable no longer pulls on the green connector.

$213.16 in parts$5.33 per unit40 units Press → or swipe to begin

The problem

The audio connection is the weakest point on the Crestron box

Small and fragile

Audio leaves the Crestron box on a small green connector on the back. Each wire is held by one tiny screw.

Nothing holds the cable

Wires run from the green connector to an XLR connector with no support. A tug, a bump or a re-route pulls on them.

Faults are hard to trace

A loose wire shows up as crackle or lost audio. The cause is hidden inside the green connector on the back.

What it looks like today

A real cable that failed

Bare wires in crimped tips go straight into the green connector. Nothing holds the cable, so every pull lands on those small screws.

A broken cable: loose wires with crimped tips going into a green connector A tangle of cables with green connectors on one end and XLR connectors on the other

Why it fails

Today a pull travels all the way to the green connector

Today

XLR cable
→
Loose wires
→
Green connector takes the load

With the box

XLR cable
→
Box, screwed to the chassis
→
Green connector, no load

The fix

A printed box that protects the green connector

The finished box fitted to the back of the Crestron box, with its screws in place and the XLR connector in its side wall

Screws to the Crestron box at three points

Carries one XLR, so the cable plugs into the box

Sums left and right to mono with four resistors

How it attaches

Screws on in three places, opens from the back

  • Two screws go through the vent holes beside the green connector
  • One screw uses the unit's own screw position
  • The XLR is held by two countersunk screws
  • The lid has four screws, so the inside stays reachable

Inside the box

Everything is screwed down and nothing floats

Straight-on view into the open box: the green connector, the wires to the XLR and the screw positions

Looking into the open box: the green connector, the resistor wiring and the XLR

The view from inside the Crestron box: the two vent-hole screws and nuts in their printed nut blocks, and the green connector in the window

From inside the Crestron box: two nuts hold the vent-hole screws

Interactive 3D model

Drag to orbit, scroll to zoom. Use Hardware and the pull-out slider.

What it does to the signal

Stereo in, mono out, with no active parts

Crestron box
→
Strain-relief box
→
Floor / wall pocket XLR ports

Four resistors

Left and right each pass through 470 Ω resistors and join at the XLR. Matching channels lose about 0.5 dB into a typical 10 kΩ line input.

Nothing to power

No electronics, no batteries, no settings. Four parts that cost cents, soldered inside the box.

Ground at the far end

XLR pin 1 is left open at the box. The shield is tied at the receiving end of the run.

The box fitted to the back of the Crestron box

Where it stands

A prototype already fits

Done: a test print fits over the green connector on a real unit and lines up with the panel.

Improved since: flush XLR pocket, cover lip, countersunk screws, full priced parts list.

Still to prove: XLR and wiring on a complete box, and a hum check.

Test fit

The first print fits on a real unit

The printed box held next to the Crestron box, with the green connector visible in its window

Window lines up with the green connector

The printed box seen end-on, showing the XLR hole and the vent-hole side

XLR hole and screw anchors in place

The printed box fitted on the back panel beside the HDMI inputs

Sits on the back panel beside the inputs

The cost

$213.16 in parts for 40 units

ItemWhat it coversCost
XLR connectors40 Neutrik NC3MPP$65.20
HardwareScrews, nuts, washers, threadlocker$69.84
ElectricalResistors and heat-shrink$24.56
FilamentBlack and white PETG, PLA$53.56
Total$213.16

$5.33

per unit

Parts only. There is no labor cost: printing and assembly happen on house shifts that are already paid. Solder is on hand.

The plan

One tested box first, then the batch

1

Order the parts

Most arrive in days; the M2.5 screws ship about Nov 18.

2

Build and test one

One complete box on a real unit: fit, wiring and a hum check.

3

Print the other 39

Fix anything the first box shows, then print and assemble the rest.

The ask

Approve $213 for 40 units

Parts for 40 strain-relief boxes, $5.33 each. One box is built and tested on a real unit before the rest are printed.

Protects the audio connectionLow costTested before the batch