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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
atmasphere's avatar
atmasphere
11,942 posts
 
I would expect woofer issues if you use the loudness function!
The more you turn down the loudness, the more it boosts the bass. It does not roll out until you are halfway across the dial on most volume controls.
I prefer not having the loudness on; in reality there is only one **sound pressure** at which the loudness setting could possibly correct, sort of like a clock that doesn't work is right 2 times a day. So its highly likely that all its doing is introducing coloration!
BTW, a ported loudspeaker that only goes to 55 Hz isn't going to have its woofer properly loaded at frequencies below that. Its very natural for it to pump around as a result. A sealed box would be less prone to this issue.

lewm
13,285 posts
 
Millercarbon, I don’t say that I’m right and you’re wrong, but I am at opposites to you with respect to all the SR products you mention in your first paragraph or two on tweaks. Not that those things can’t make an audible difference, but I cannot imagine a more profligate way to spend money for what could be very tiny results.And none of those items will address the complaint that brought the OP to this forum.
branden_8091 OP
60 posts
 
I've done some critical listening and found that unless my speakers are above a whisper, the loudness kind of makes them muddy anyway.  If I play a smoother record (especially in the inner tracks), the woofer pumping is not there, even at high volumes (loudness off).
I guess the issue is solved! Thanks to all.
glupson
7,842 posts
 
That is what subsonic filters on amplifiers used to be for, I think.
rdk777's avatar
rdk777
577 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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