For those having problems hearing the difference here's the list from best to worst. Your results might vary.
NASA grade ceramics
Tempered high carbon steel cones
Aluminum cones
Brass cones
Carbon fiber cones
Nothing
Rubber and Sorbothane
Lead
NASA grade ceramics
Tempered high carbon steel cones
Aluminum cones
Brass cones
Carbon fiber cones
Nothing
Rubber and Sorbothane
Lead