40 mm loudspeaker envelope (the speaker in the thermoacoustic driver cap) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/loudspeaker-envelope-40mm/  (CC BY 4.0)
Basis: Overall Ø40 × 25 and the step diameters measured from the manufacturer's published model of a 40 mm speaker (Adafruit #3968); drawn as a stepped envelope, nothing copied
Catalog version: 2026-10-20

Sizes: see table below
- A stepped envelope of a common 40 mm speaker: the space it takes, not its parts. Front rim Ø40 × 3 with the cone behind it, a Ø34 × 4 step, the Ø28 basket and the Ø20 magnet; 25 mm overall.
- In the 2 in driver cap it sits rim down in the Ø40 × 6 socket, cone toward the gas through the cap's Ø28 port; the basket and magnet stand above the cap.
- As an alternator: the gas pressure moves the cone, the voice coil moves in the magnet's field and gives a voltage at the terminals. A small speaker gives milliwatts to a fraction of a watt; see the build lists for the model's acoustic power at the cap.

feature  value
step 1  Ø40 from 0 to 3
step 2  Ø34 from 3 to 7
step 3  Ø28 from 7 to 17
step 4  Ø20 from 17 to 25

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Adafruit (CAD parts repository, MIT): #3968 Speaker 40mm: overall Ø40 × 25 and the step diameters measured from the published model; nothing copied — STEP — MIT; dimensions only — https://github.com/adafruit/Adafruit_CAD_Parts/tree/main/3968%20Speaker%2040mm
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/loudspeaker-envelope-40mm/index.json
API: https://xemstudio.com/api/geometry?object=loudspeaker-envelope-40mm