Oddly enough the rehearsal studios i use have about 12 or 13 rooms all have Ampeg 810 with usually an EBS HD360 head. Depending on room i've noted differences in tone from the cabs with amp settings remaining same. Room sizes vary a little but not much.. I've always suspected that some speakers have been replaced but no idea wheteher the good cabs have the originals speakers or replacements ? Maybe they are different age cabs ?
The good ones sound fuller and warmer yet still retain a sharpness when playing faster passages. Others are more woolly sounding where definition isn't so good. Rooms are all laid out in same manner with Marshall guitar amp one side of drums and bass cab on other side (snare side).
That to me does suggest that different speakers in same cabs will sound different. Again its probably just me that notices it as no-one else has said anything. They probably don't listen to the bass anyway. They have commented on guitarists sound tho.
Dave