Why are my woofers pumping?

Hi-

I had the exact same issue with a Kuzma Stabi R table, 4P arm and ZYX Universe II cartridge. Initially, I just had it on my audio rack and the pumping was really bad. Then I added a HRS R1X platform and it got better, but still there.  I called HRS and they suggested replacing the regular feet with low frequency feet. Also was communicating with Franc Kuzma who agreed with HRS and said the reason was that the table and audio rack got into an acoustic feedback resonance. Just got the feet from HRS and it seems problem is solved now - overall sound also significantly better.

Hi rdk777This agrees with my own experience, especially regarding the VPI HW19 player I used before. Every little thing I could do to it, regarding the platform, feet, etc, made a change. Air (bike tires), a large bright star sand box, ceramic feet, you name it!
Now, with the maglev system of my new player, Hanss T30, it does not seem so tempting. It rests directly on my very heavy stone rack. Maybe HRS might improve things  even there. I note that Aesthetix recommends HRS feet under their boxes (like my Io phono stage).

Just a little update. Testing Pink Floyd: Echoes, with the Lyra Atlas replacement I got back in August, 2018. Could it be, that the pumping woofer syndrome is caused by wear of this cartridge? Short answer: no. The new cartridge has now run ca 1200 hours. I don’t see or hear any problems. The woofers DO show subsonic energy (they move/vibrate although I don’t hear sound), yet it is nothing like the heavy pumping I had with the 2013 Atlas.

I think the diagnosis is fairly clear here. First, this is a really wide frequency recording, especially in the opening section, and therefore, a good diagnosis tool for lowest bass performance (the treble is extended too, exceptionally life-like). Your copy of Meddle may not have this - it concerns my second press, cut by H T Moss at EMI UK). It was made to challenge your stereo.

The reason why it created woofer pumping was mainly related to the poor / worn state of my 2013 Atlas cartridge. The arm, player etc had nothing to do with it. A few months after I discovered the woofer pumping, the stylus fell off the cantilever. For no clear reason. I think it had received a bump or shock earlier - from a not so clean or dusty record - and that the woofer pumping was the result of that. It had got loose. I cannot prove any of this, but it seems the most likely explanation. Needless to say I have improved my record cleaning. Even if a record looks clean, I always use a Mofi brush before play. A little speck of dust, or a hair, can be a big hurdle for the stylus.

 

A few months before I noticed the woofer pumping with the 2013 Atlas, it was in for a check at a local service shop. Soon after I noticed the pumping, the diamond dropped from the cantilever. So it *may* be that it received some tough handling at the shop - and not from my records, even if some of them were dusty. I will never know for sure.