There have been other methods suggested in the past. A particularly popular one was offered byVictor Khomenko in the late 90s and seems to have been widely accepted since. In our experiments, we’ve found that, while this method works very well at a given frequency (most people seem to use a 1 KHz tone for this purpose), it is unfortunately not consistent throughout the frequency range found in music. We discovered that after adjusting the azimuth for perfect balance at 1 KHz with this method, voltage readings with a 100 Hz and a 8 KHz tone give widely different results; one channel would be greatly emphasized at the lower frequency, and the other one at the higher frequency. So while the method is theoretically sound, it fails to address the reality of the musical signal, which is far more complex than a single sine tone. So, until a better and more reliable method is established, our ears will do nicely... and they’re free...
Additional note: to be fair, it has been suggested that crosstalk is not constant on all cartridges. Some cartridges (a few?) demonstrate excellent consistency across their frequency range, while many don’t. For what it’s worth...
ps for measuring timber I’ve found a tape measure works quite well 😏 , measuring timbre requires a depth of musical experience and a good ear, no electronics can help here