Hi guys, I bought Kef Celeste speakers. The oval bass units differ, I need to know if they are the same, cause the guy replaced the one unit, they look the same in front but the back looks different, still round magnets on both, one has a metal block under the other magnet and the speaker frame differ, one code on the woofer says 6171, and the other one code says 0176 see pics, or are they basically the same? Regards