Purchased this cardioid mic to solve the feedback problems in a setup;
Our setup works well with cardioid standard mics, all our tested Omni lavaliere mics are unusable due to feedback issues. And decided to purchase this Sennheiser MKE 40-EW cardioid mic which turned to be very close in feedback with the Omni mics, therefore we have returned it for not solving our problem.
Conclusion: it is a great-sounding microphone but is not usable in the proximity of the speakers or high stage volume also not much better in terms of feedback issues compared to their Omni counterparts.