Hello Aleks,
thanks for your quick answer. Crawling the WEB let appears, there's some strange things in conversion with Inkscape, Adobe Illustrator and others (72 dpi, 90 dpi, 96 dpi...). Somebody reported there's a 1.25 ratio for unknown reasons with these software.
That's right, I made a workaround, applying a 125% scale to CDR objects in Inkscape, before saving as .SVG. And it worked ! In FreeCAD my W5 hole is 120mm, speaker height & width are fine, and pin locator are a classical 8mm diameter.
I'll made that clone with a CNC, machining a sandwich of wood plate (16 + 22 + 22 + 22 + 22). Today my speakers just arrived from www.rumoh.eu. Please find attached a screenshot of the FreeCAD design (FE85 not yet integrated).
Another question: I'am a bit surprised: I didn't seen anywhere absorber inside. Could you confirm ?
I am electronician, and next step (in a far futur) will be to transform it in an active speaker, with DSP and 3 way amplifier...