Maybe you found out about Otto Klemm from my book, which says "Otto Klemm (1920) published much more detailed experimental results, also in
1920, and found a time-difference threshold of about 20 microseconds in one subject, and even less than 10 microseconds in another!"
Or maybe not, since I didn't abbreviate Archiv für die gesamte Psychologie and had the longer title:
Klemm, O. (1920). “Untersuchungen über die Lokalisation von Schallreizen. 4. Mitteilung: Über den Einfluß des binauralen Zeitunterschiedes auf die Lokalisation,” Archiv für die gesamte Psychologie 40, 117–146.
In general, I can provide copies of references on request.
> found in the Innsbruck Library across the street from MED-EL and scanned for me when I asked on this list in March 2011. I'll send it separately.