def response(self, parameters):
        r"""Return the forward response in base dimensions
        :math:`\hat{\sigma }(\omega ) = \sigma _\infty \left(1 - \sum_i \frac
        {m_i}{1 + (j \omega \tau_i)^c_i}\right)`

        Parameters
        ----------
        pars:

        Returns
        -------
        response: Nx2 array, first axis denotes frequencies, seconds real and
                  imaginary parts
        """
        # get a config object
        self._set_parameters(parameters)
        terms = self.m / (1 + (1j * self.w * self.tau) ** self.c)
        # sum up terms
        specs = np.sum(terms, axis=1)
        ccomplex = self.sigmai * (1 - specs)

        response = sip_response.sip_response(self.f, ccomplex=ccomplex)

        return response