High efficiency 21 cm ( 8" ) wide range unit, paper cone, basket and ring = bronze without lead SN12, pole pieces made of very mild steel < 0.20 % carbon in a pot shape with central ALNICO 3SC magnet : all fields is in the gap and magnetically proof ( TV… )
Each driver part is controlled and measured all along the manufacturing process. Each driver is put under a very serious pre-running and then measured in order to match pairs with max tolerance delta as 0,1gr. on mobile equipment mass, 0.1 Ohms on d.c. resistance, 1Hz on resonance frequency, is numbered and life guaranty ( first owner ) .
