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Unsolvable Woofer Pumping (Phono only)

I'm at a loss for trying to find the source of my "woofer pumping."  It's most noteworthy when playing something that is mostly/all treble, and the woofers of my Focal Aria 906s are going nuts (inaudibly, of course).  Turntable is a Debut Carbon with Ortofon 2M Blue.

Initially I was told it's an isolation problem, so I better isolated my TT, even put it right on the concrete floor to test!  Next I thought maybe a problem with the TT itself, so tried a couple others, no change.  So I figured it must be acoustic feedback, as with the TT stopped and stylus on a record, I could produce woofer pumping by tapping on certain parts of my stand...but it is also not this! I turned off my amplifier and recorded from the pre-out to a Tascam digital recorder and played that back afterwards and the pumping STILL happened! So I tried an Schiit Mani phono stage, no change in woofer pumping...I was sure it had to be my pre-amp...

So a local audiophile came over with a couple of pre-amps and we tried those.  The only time the problem went away was when the subsonic filter that one had was engaged.  So, I've ordered some Harrison Labs "FMODs" (20Hz high pass) to see if they will help.  If they do, I may order a KAB RF1 one day...but don't want to spend that much if I don't have to.
Any other ideas on what could cause this?!

tl;dr: Woofer pumping not caused by isolation, acoustic feedback, phono/preamp or a compliance issue...what's happening?!

branden_8091

Showing 1 response by rdk777

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rdk777
568 posts
 
I had a very similar issue occurring at higher volumes and and only at the beginning of the track as soon as the needle dropped (before the music played) - the woofer seemed normal once the track started playing. Brand new Stabi R - so it bugged the crap out of me. After much fidgeting, I narrowed it down to my Google Wifi router which was in proximity to the turntable. After moving the Google Wifi to a lower platform on my rack, most of the issue seemed to go away. Loudness on my ARC Ref 2SE is on - there's no other way to listen to it. Any chance you have a router nearby?

Currently, the acoustic feedback (that's what I'm calling it) is 95% better.  HRS suggested that I try replacing the regular feet on my platform with low frequency feet. I just got them today - I'm hoping they'll work.
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