@ted_denney
The same way we build everything, sound engineering principles with lots of listening tests during the development process when making decisions between competing engineering principles, followed by more listening tests.
Unless you are involved with only the listening tests, you should know that "good engineering" involves a copious amount of measurement of the right things, followed by more measurements. It has to start an end with measurement otherwise the science cannot advance or sustain. People get old and die, even golden ears. A company that relies ONLY on listening opinions is quackery. Listening tests and measurements go hand in hand. That, my friend, is good engineering.
