power conserving filter

My question is about the working principle of a band pass filter. Do we conserve the incoming power or do we lose power?

Suppose we have an incoming power, then a power divider. On each of the arms of the power combiner, there is a band pass filter of dF1 and dF2, having dF=dF1+dF2.
Now, we combine the two signals. Have we lost power over the bandwidth dF?

Thank you for your help

Yes and it will be 6dB loss ideally