resistor values of a 4th order bessel high pass filter
From wiki, the transfer function polynomials for several Bessel filters are: -









If you took two 2nd order filters and multiplied the polynomials you do not end up with the polynomial of a 4th order Bessel filter. You end up with this: -

\$s^4 + 6s^3 + 15s^2 + 18s + 9\$

This informs you that cascading two independent 2nd order Bessel filters does not produce a 4th order Bessel filter or, in other words you have to calculate the values of the components in both 2nd order filters taking into account that you are trying to implement a 4th order system. You might get lucky of course but if you just cascade 2 2nd order Bessel filters it won't be a 4th order Bessel filter.

It's not just Bessel filters that this rule applies to.

Here's a website that might help. The calculator appears to keep a common value for the capacitors used but there are 6 resistors all having different values: -