The passive speaker trembled loudly enough at low frequencies. In other words, the case's sealing is compromised (without affecting the phase inverter's opening). And it wasn't on the one that was in use. I had to use sealant to go through the connector's joints and along the borders of the backplate (with the entry). I used sealant to treat the phase inverter as well. The deficiency wasn't fixed until all these procedures were completed. Link to a demonstration video
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