I only mentioned cabinet resonance as one source of timbre-like defect, not the only one The dreaded cupped-hand resonance (several possible causes) is another common defect, one that is especially audible with human voices, heard as an alteration of timbre, sometimes described a nasal.Okay ... I thought that you had, since you used the word "components" (plural).
Is it then safe for us to assume that the only portion of the reproduction chain that can perhaps contribute a change of timbre is the loudspeaker? (If I remember correctly, acoustic feedback through a cartridge won't do it.)
By this post, I am not yet willing to agree that speaker resonance can cause an effect that listeners will identify with a change in timbre ... at least not consistently. (Changing output levels and varying spectral content seem to prevent that.)
Perform in a few hundred venues and you start thinking about room acoustics in terms of timbre, too - boomy, dry, crisp, clangy, etc. After a while, even neutral starts to sound like a timbre.
Instruments typically consist of an exciter (reed, lips, bow, etc.) and a resonator (often complex). Put a musical instrument in a room and the instrument becomes the exciter and the room becomes the resonator - room excited by instrument: a new timbre. Move the instrument to another room and you create a new timbre. Timbre quite literally doesn't happen in a vacuum.