Vocal cords and loudspeakers are fundamentally opposite devices - why?
Fascinating. To me the essential point is that the vocal cords* are self-evidently created from pliable moist tissue, nourished by a warm blood supply and under muscular control. They are not like our bones or nails. Taken together, that means that the vocal cords are extremely well mechanically damped, and in audio we respect damping because it opposes the character we most seek to avoid: ringing otherwise known as undamped oscillation. The real live human voice is produced by wet, damped vocal cords at 38 deg. C with their normally smooth even sonic character and they are conceptually the opposite of what you find actually producing sound inside the loudspeaker. The speaker uses hard, rigid metal, plastic and cloth moulded parts at about 20 deg.C (ambient temperature) none of which have any 'give'. You can see then that if any or all of the speaker's parts have a tendency towards self-oscillation (ringing) there is no warm spongy tissue to damp that tendency.
Originally Posted by STHLS5
This very low damping in the loudspeaker parts has some important consequences:
- If the speaker does 'ring' at some frequency or other, that may or may not be masked by music but
- if clean, well recorded speech is reproduced over the speaker the ear may hear the unnatural character of the speaker imposed on what we expect natural speech to sound like and
- once the ear has latched onto the self-evident loudspeaker coloration the subconscious mind cannot relax and
- the listener is then in a state of psychological tension as he is not completely convinced he is in the presence of a real, live human
The reason I have used human speech for so long as the primary arbiter of loudspeaker sonic quality is because most of the unwanted characteristics exhibited by loudspeakers cannot be heard in the live voice. Real human voice boxes cannot sound 'ringy' or 'brittle', descriptive terms we associate with hard, rigid materials.
Perhaps surprisingly, the various colorations we associate with poor loudspeakers were characterised and named as far back as 1938 - before WW2 in the 78 era. From my archives, I've scanned this foolscap sheet to illustrate the point that speaker colorations were identified at the very start of the loudspeaker era, and are still with us to one extent or another as loudspeakers with their rigid parts try to mimic the human voice with its soft parts.
*I cannot decide if the correct spelling is cord or chord. Any ideas?
Alan A. Shaw
Harbeth Audio UK