ACR MLG VECTORED INTO CONFLICT WITH ACR LGT WHEN DESCENT CLRNC WAS NOT RECEIVED; RESULTING IN LESS THAN STANDARD SEPARATION.

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MLG X WAS ON DOWNWIND FOR RWY 14R AT O'HARE. COPLT WAS FLYING. ACFT WAS AT 5000'; 210 KTS AND ON A 320 DEG HDG. CTLR GAVE US A R TURN TO 90 DEG AND I ACKNOWLEDGED. AS WE STARTED OUR TURN WE SAW LGT Y AT 1 O'CLOCK AND LEVEL WITH US. CTLR SAID 'HURRY YOUR TURN TO 130 DEG' AND WE ACKNOWLEDGED. A SUPERVISOR THEN CAME ON AND ASKED US TO CONFIRM WE WERE DSNDING TO 3000'. I SAID; 'NO; BUT WE'LL START DOWN NOW.' THE SUPERVISOR ASKED IF WE HAD LGT Y IN SIGHT AND I SAID WE DID. SUPERVISOR GAVE US A 50 DEG HDG TO PASS BEHIND LGT Y. WE WERE THEN SLOWED TO 170 KTS. AFTER PASSING BEHIND LGT Y WE WERE GIVEN A VECTOR BACK TO FINAL AND CLRED FOR A VISUAL TO 14R. I TALKED TO THE SUPERVISOR ON THE PHONE TO SEE WHAT HAD HAPPENED. AT SOMETIME ON DOWNWIND THERE MUST HAVE BEEN A BLOCKED XMISSION TO US--TO DSND TO 3000' AND SLOW TO 170 KTS. I DID NOT RECEIVE NOR ACKNOWLEDGE THIS CALL. BECAUSE WE WERE AT 5000' AND 210 KTS A CONFLICT OCCURRED. SUPPLEMENTAL INFO FROM ACN 89816. I REMEMBER HEARING A BLOCKED XMISSION ON DOWNWIND; AND IT MAY HAVE BEEN FOR US; BUT THE CTLR MAY HAVE ASSUMED THAT IT WAS RECEIVED (BUT NOT ACKNOWLEDGED). OUR DOWNWIND SPD OF 210 WAS INCOMPATIBLE WITH SEQUENCING 170 KT ACFT; BUT THE CTLR MIGHT HAVE BEEN DISTRACTED AND THOUGHT THE SEQUENCING WAS ACCEPTABLE.