My cartridge/tonearm combo is perfect on paper and confirmed thorough a test record. Nevertheless, I would get woofer pumping on some records, but not others, which clearly indicates the problem lies with the record, not the system. This also confirms what KAB describes on its website about the subsonic/infrasonic frequencies being imparted on the recording by the disc cutting system. The KAB filter solved the problem and I never looked back. I think the argument about sound degradation is silly; you actually improve the sound by not wasting your amp power trying to amplify infrasonic frequencies and your speakers trying to reproduce them.
If by some miracle your system is free of rumble problems, God bless you, but for those with well matched carts and tonearms and no isolation problems still experiencing woofer pumping on some records, a good quality subsonic filter is the answer.
If by some miracle your system is free of rumble problems, God bless you, but for those with well matched carts and tonearms and no isolation problems still experiencing woofer pumping on some records, a good quality subsonic filter is the answer.