A quick comparison of how the United UT-Twin87 sounds with the RF filter engaged vs bypassed. It ships with the RF filter bypassed and you can hear what a big difference it makes when you engage the RF. Instructions how to switch it can be found in the Twin87 manual. Twin87 manual: https://avantone-cms.s3.amazonaws.com/3613061b-6991-44a7-a400-de52a23979c2/United-UTTwin87-OwnersManual.pdf And remember... you can get 11 percent off your order at JRRShop.com with coupon code MICROPHONEASSASSIN