# Thermoacoustic driver cap: ISO 2852 cap with a Ø40 speaker socket, 1.5, 2 and 3 in

> How do I mount a speaker on a tri-clamp thermoacoustic tube?

- Category: Stirling engines › Thermoacoustic & fluidyne
- Kind: Hardware
- Basis: ISO 2852 cap face; Ø40 × 6 socket for a 40 mm speaker frame; Ø28 opening to the tube
- Page: https://xemstudio.com/objects/thermoacoustic-driver-cap/ · JSON: https://xemstudio.com/api/geometry?object=thermoacoustic-driver-cap · Plain text: https://xemstudio.com/objects/thermoacoustic-driver-cap/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- An ISO 2852 end cap that holds a 40 mm speaker on the resonator: as a driver it makes a thermoacoustic refrigerator, as a load it turns the engine's sound into a few milliwatts.
- On the back of the 6 mm cap: a Ø48 × 8 boss with a Ø40 socket 6 mm deep (floor 8 mm above the face) and a Ø28 opening through to the tube. Overall 14 mm.
- Flange Ø50.5 / 64.0 / 91.0 for 1.5 / 2 / 3 in.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| speaker socket | Ø40 | 40 mm speaker frame | socket | driver-cap-* |
| driver-cap face | ISO 2852 | ferrule face + Type B gasket | clamp | driver-cap-* |

## Sizes

| size_in | flange_od_mm | speaker_socket_mm | opening_mm | height_mm |
|---|---|---|---|---|
| 1.5 | 50.5 | Ø40 × 6 | 28 | 14 |
| 2 | 64.0 | Ø40 × 6 | 28 | 14 |
| 3 | 91.0 | Ø40 × 6 | 28 | 14 |

## Where the files are

- Wikipedia: [Thermoacoustic heat engine](https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine) — web — CC BY-SA 4.0 (text)
- G. W. Swift (LANL): [Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (textbook; DeltaEC software free)](https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/) — web, software — LANL (verify at link)
- NASA (NTRS, public domain): [Thermoacoustic Stirling heat engine for space power](https://ntrs.nasa.gov/search?q=thermoacoustic%20Stirling) — PDF — US Government work, public domain
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/thermoacoustic-driver-cap/index.json

- driver-cap-1.5in-40mm-speaker: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-1.5in-40mm-speaker.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-1.5in-40mm-speaker.stl) — 1.5 in ISO 2852 cap with a Ø40 × 6 socket (floor 10.5 above the face) for a 40 mm speaker, Ø28 port through to the bore (thermoacoustic refrigerator driver / engine load)
- driver-cap-2in-40mm-speaker: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-2in-40mm-speaker.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-2in-40mm-speaker.stl) — 2 in ISO 2852 cap with a Ø40 × 6 socket (floor 8 above the face) for a 40 mm speaker, Ø28 port through to the bore (thermoacoustic refrigerator driver / engine load)
- driver-cap-3in-40mm-speaker: [STEP](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-3in-40mm-speaker.step) · [STL](https://xemstudio.com/files/hardware/thermoacoustic-stacks-and-resonators/driver-cap-3in-40mm-speaker.stl) — 3 in ISO 2852 cap with a Ø40 × 6 socket (floor 8 above the face) for a 40 mm speaker, Ø28 port through to the bore (thermoacoustic refrigerator driver / engine load)

## How it fits

### Goes in or on
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/): ISO 2852 face on the resonator's open ferrule

### Connects to
- [Speakers, amplifiers and microphones: 3 in, 40 mm, enclosed, STEMMA speaker, MAX98357, I2S/PDM mics](https://xemstudio.com/objects/adafruit-audio-speakers-mics/): 40 mm speaker in the Ø40 socket
- [Thermoacoustic stack for tri-clamp spools: Ø34.8, Ø47.5 and Ø72.9, honeycomb and spiral](https://xemstudio.com/objects/thermoacoustic-stack/): drives or loads the resonator the stack sits in

### Alternatives
- [Linear alternator mover: Ø35 carrier for 16 Ø10 × 3 magnets](https://xemstudio.com/objects/linear-alternator-mover/): piston load for more power

### Also needed
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/): clamp and gasket on the face

## Questions

**What speaker fits the driver cap?**

A 40 mm frame in the Ø40 × 6 socket; the cone faces the tube through a Ø28 opening.

**Can a thermoacoustic engine make electricity?**

A speaker in this cap works as a generator at milliwatt level; for more, a piston on the linear alternator.

## Fits with

- [Thermoacoustic stack for tri-clamp spools: Ø34.8, Ø47.5 and Ø72.9, honeycomb and spiral](https://xemstudio.com/objects/thermoacoustic-stack/)
- [Speakers, amplifiers and microphones: 3 in, 40 mm, enclosed, STEMMA speaker, MAX98357, I2S/PDM mics](https://xemstudio.com/objects/adafruit-audio-speakers-mics/)
- [Tri-clamp clamp, two-bolt: every flange size ½ to 4 in](https://xemstudio.com/objects/tri-clamp-clamps/)
- [Linear alternator mover: Ø35 carrier for 16 Ø10 × 3 magnets](https://xemstudio.com/objects/linear-alternator-mover/)
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/)