CREATE TABLE "past_production" (
  "headphone_model" text,
  "headphone_class" text,
  "sensitivity_d_b" text,
  "impedance_ohms" real,
  "driver_matched_d_b" text,
  "construction" text,
  "earpads" text,
  "termination" text,
  "succeeded_by" text
);

Question: Name the number of headphone class for sr100
SQL: SELECT COUNT("headphone_class") FROM "past_production" WHERE "headphone_model"='SR100';

Question: Name what succeeded by for foam
SQL: SELECT "succeeded_by" FROM "past_production" WHERE "earpads"='Foam';

Question: Name the headphone model for succeeded by sr125
SQL: SELECT "headphone_model" FROM "past_production" WHERE "succeeded_by"='SR125';

Question: Name the driver matched db for joseph grado signature
SQL: SELECT "driver_matched_d_b" FROM "past_production" WHERE "headphone_class"='Joseph Grado Signature';