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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
branden_8091 OP
60 posts
 
@stringreen Interesting.  There is one about 15km away...I will try a 'cheater cord' to ground to my house rather than to the pre-amp's grounding point.
branden_8091 OP
60 posts
 
@mijostyn I was unaware...I thought subs were generally un-powered. I may be trying out some Harbeth speakers this weekend. Quite excited for that. I went to a few hi-fi shops around today and talked to them about this...have a few more things to try so I hope it is solved!!
lewm
12,560 posts
 
Since the advent of small, high power, Class D solid state amplifiers and the rise in popularity of home theater, about 20 or more years ago, there have appeared in the market a myriad of small, self-powered subwoofers that typically also have adjustable crossovers and built-in attenuators (so the output can be balanced with that of the main speaker).  Try a pair with your present speakers, which in my opinion are probably excellent, as I have high regard for Focal.  What you are doing is shifting the "problem" (woofer dancing) from the main speakers to the subwoofers, which you can cross over to at very low frequencies, like 50 or 60 Hz.  The result will be a cleaner sound AND more extended bass.  Anyway, that's what I would do in your situation.  I wouldn't necessarily swap Focal for Harbeth, unless you are truly dissatisfied with the Focals for other unrelated reasons.
branden_8091 OP
60 posts
 
Neat. I was unaware that that's how they worked.  I'm not dissatisfied with them per sé, just a little underwhelmed in some cases.  A sub-woofer seems like it may be a viable solution though!  One of my potential upgrade paths are the 936s, simply because they have more range/volume.  Maybe a sub would be a viable alternative!
I'm just trying the Harbeths for fun (mostly)...they offered to let me borrow them so I said sure, why not? :)
psag
518 posts
 
What about other sources, such as a CD player? If the problem persists with other sources, its likely to be an amplifier problem.
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