Aha! In an ideal world, a transducer (microphone or speaker) should have no "timbre" as it's input spectrum should match it's output, ie. it should be "flat". Warm, bright, or other descriptive would indicate some deviation, possibly euphonic, from flat.
If someone describes a speaker as having a nice timbre, it is likely a euphonic coloration. I would guess most audiophile speakers fall into that category, whereas true studio monitors would more likely be flat.
Timbre matching would mean all speakers within a set have the same coloration. Maybe different frequency extensions, but the same general peaks and valleys within that range. it's those peaks and valleys that make the speaker "nasal" or "honky" or "boomy"
That's my take.
