  The mechanism of channel coupling via decay products is used to study energy
shifts, level mixing as well as the possibility of new near-threshold
resonances in $c\bar c, b\bar b$ systems. The Weinberg eigenvalue method is
formulated in the multichannel problems, which allows to describe
coupled-channel resonances and wave functions in a unitary way, and to predict
new states due to channel coupling. Realistic wave functions for all
single-channel states and decay matrix elements computed earlier are exploited,
and no new fitting parameters are involved. Examples of level shifts, widths
and mixings are presented; the dynamical origin of X(3872) and the destiny of
the single-channel $2^3P_1(c\bar c)$ state are clarified. As a result a sharp
and narrow peak in the state with quantum numbers $J^{PC}=1^{++}$ is found at
3.872 GeV, while the single-channel resonance originally around 3.940 GeV,
becomes increasingly broad and disappears with growing coupling to open
channels.
