The file has two sizes (lengths) for use in larger N scale diesels. The files can be downloaded from TinkerCad (AutoCad) in several formats for printing. Easily scaled for HO or other scales.
https://www.tinkercad.com/things/lU4jylmiYrp-sugarcube-speaker-cases-with-extra-volume-2-sizes
Large volume internally ported SugarCube speaker case 2023-10-28
Large volume cases for use in larger n scale diesel