{
 "version": "2026-10-20",
 "license": "Dimension sheets are written by Xem Studio from the cited sources and are free to use (CC BY 4.0, attribute 'Xem Studio'). Linked files belong to their publishers under the license shown; Xem Studio does not host them. 'license_verified: false' means the license shown is from memory or the publisher's page as last read and should be confirmed at the link before commercial use.",
 "slug": "thermoacoustic-driver-cap",
 "name": "Thermoacoustic driver cap: ISO 2852 cap with a Ø40 speaker socket, 1.5, 2 and 3 in",
 "kind": "hardware",
 "category": "Stirling engines",
 "group": "Thermoacoustic & fluidyne",
 "year": null,
 "question": "How do I mount a speaker on a tri-clamp thermoacoustic tube?",
 "tags": [
  "thermoacoustic",
  "speaker",
  "driver",
  "tri-clamp",
  "end cap",
  "stirling",
  "long earth society"
 ],
 "aliases": [
  "thermoacoustic speaker mount",
  "tri clamp speaker cap",
  "thermoacoustic refrigerator driver",
  "40mm speaker tri clamp"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": true,
 "free_files": 3,
 "url": "https://xemstudio.com/objects/thermoacoustic-driver-cap/",
 "sheet_txt": "https://xemstudio.com/objects/thermoacoustic-driver-cap/sheet.txt",
 "sheet": {
  "basis": "ISO 2852 cap face; Ø40 × 6 socket for a 40 mm speaker frame; Ø28 opening to the tube",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "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."
  ],
  "table": {
   "columns": [
    "size_in",
    "flange_od_mm",
    "speaker_socket_mm",
    "opening_mm",
    "height_mm"
   ],
   "rows": [
    [
     "1.5",
     50.5,
     "Ø40 × 6",
     28,
     14
    ],
    [
     "2",
     64,
     "Ø40 × 6",
     28,
     14
    ],
    [
     "3",
     91,
     "Ø40 × 6",
     28,
     14
    ]
   ]
  }
 },
 "sheet_text": "Thermoacoustic driver cap: ISO 2852 cap with a Ø40 speaker socket, 1.5, 2 and 3 in — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/thermoacoustic-driver-cap/  (CC BY 4.0)\nBasis: ISO 2852 cap face; Ø40 × 6 socket for a 40 mm speaker frame; Ø28 opening to the tube\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 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.\n- 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.\n- Flange Ø50.5 / 64.0 / 91.0 for 1.5 / 2 / 3 in.\n\nsize_in  flange_od_mm  speaker_socket_mm  opening_mm  height_mm\n1.5  50.5  Ø40 × 6  28  14\n2  64.0  Ø40 × 6  28  14\n3  91.0  Ø40 × 6  28  14\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Wikipedia: Thermoacoustic heat engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine\n- G. W. Swift (LANL): Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (textbook; DeltaEC software free) — web, software — LANL [verify license at link] — https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/\n- NASA (NTRS, public domain): Thermoacoustic Stirling heat engine for space power — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=thermoacoustic%20Stirling\n- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/thermoacoustic-driver-cap/index.json\nAPI: https://xemstudio.com/api/geometry?object=thermoacoustic-driver-cap\n",
 "sources": [
  {
   "publisher": "Wikipedia",
   "title": "Thermoacoustic heat engine",
   "url": "https://en.wikipedia.org/wiki/Thermoacoustic_heat_engine",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "G. W. Swift (LANL)",
   "title": "Thermoacoustics: A Unifying Perspective for Some Engines and Refrigerators (textbook; DeltaEC software free)",
   "url": "https://www.lanl.gov/org/ddste/aldps/materials-physics-applications/condensed-matter-magnet-science/thermoacoustics/",
   "formats": [
    "web",
    "software"
   ],
   "license": "LANL",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "NASA (NTRS, public domain)",
   "title": "Thermoacoustic Stirling heat engine for space power",
   "url": "https://ntrs.nasa.gov/search?q=thermoacoustic%20Stirling",
   "formats": [
    "PDF"
   ],
   "license": "US Government work, public domain",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Long Earth Society",
   "title": "Engine builds",
   "url": "https://longearthsociety.com/engineering/",
   "formats": [
    "web",
    "video"
   ],
   "license": "LES site",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "thermoacoustic-stack",
  "adafruit-audio-speakers-mics",
  "tri-clamp-clamps",
  "linear-alternator-mover",
  "tri-clamp-spool"
 ],
 "fits": [
  {
   "role": "Goes in or on",
   "items": [
    {
     "slug": "tri-clamp-spool",
     "why": "ISO 2852 face on the resonator's open ferrule"
    }
   ]
  },
  {
   "role": "Connects to",
   "items": [
    {
     "slug": "adafruit-audio-speakers-mics",
     "why": "40 mm speaker in the Ø40 socket"
    },
    {
     "slug": "thermoacoustic-stack",
     "why": "drives or loads the resonator the stack sits in"
    }
   ]
  },
  {
   "role": "Alternatives",
   "items": [
    {
     "slug": "linear-alternator-mover",
     "why": "piston load for more power"
    }
   ]
  },
  {
   "role": "Also needed",
   "items": [
    {
     "slug": "tri-clamp-clamps",
     "why": "clamp and gasket on the face"
    }
   ]
  }
 ],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [
  {
   "feature": "speaker socket",
   "exact": "Ø40",
   "mates": "40 mm speaker frame",
   "fit": "socket",
   "files": "driver-cap-"
  },
  {
   "feature": "driver-cap face",
   "exact": "ISO 2852",
   "mates": "ferrule face + Type B gasket",
   "fit": "clamp",
   "files": "driver-cap-"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. Typical FDM: hole +0.0 to +0.1 mm on diameter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. Typical FDM: +0.2 mm.",
  "run": "turns or slides in use: pin in a link, rod through a guide. Typical FDM: +0.3 mm.",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. Typical FDM: +0.3 mm.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What speaker fits the driver cap?",
   "a": "A 40 mm frame in the Ø40 × 6 socket; the cone faces the tube through a Ø28 opening."
  },
  {
   "q": "Can a thermoacoustic engine make electricity?",
   "a": "A speaker in this cap works as a generator at milliwatt level; for more, a piston on the linear alternator."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "driver-cap-1.5in-40mm-speaker",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "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",
   "note": "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)"
  },
  {
   "file": "driver-cap-2in-40mm-speaker",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "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",
   "note": "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)"
  },
  {
   "file": "driver-cap-3in-40mm-speaker",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "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",
   "note": "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)"
  }
 ],
 "markdown": "https://xemstudio.com/objects/thermoacoustic-driver-cap/index.md"
}