Why are my woofers pumping?

O_holter:  I'm convinced your problem comes from acoustical feedback. With a TT, placement is vital. I too had the same problem.  After months of experimenting, I found that TT platform isolation cured my problem. I built a suspended platform using heavy duty dampened springs and cables. (my room is on a suspended floor on the upstairs portion of my house that exasperates the problem)  I also noticed feedback on my Theta Miles CD player, when playing anything with a lot of elf and high db levels. I installed four steel cones on the bottom of the player and now I enjoy outputs of 90 db+, without any adverse effects on both playback systems. Most rooms have areas, where the low frequency is somewhat exaggerated. Be sure your TT, as well as your CD transport is not in one of these locations. 

I am mystified. Why do i see woofer pumping playing Echoes on my small cottage system which is 6db down at 42hz and probably not audible below ca 38hz? All hail to DSD? I play a rip / recording of the same original vinyl that gives pumping in the main system. Recorded in DSD on Tascam Da3000. Playback by the little Fiio x3 player, which does native DSD, to a Ming Da integrated tube amp and Aurum Cantus Leisure 3 SE speakers. All very good but i seriously doubt if this system is capable of doing anything down at 7hz where my cart-arm resonance problems are.

Handymann - much appreciated and relevant. I did a lot of platform and feet mods with my Vpi Hw19 to good effect but mods have so far little effect on the Hanss t30 with its maglev feet. And - my vinyl recordings are made with the main speakers silent or very subdued. So I doubt acoustic feedback is the main culprit in this case.

The woofers on the Aurums are smaller but the behavior is similar to the Audiokinesis woofers. Some sound related vibrations but also pumping in and out. Yet I dont hear this movement at least not directly. Using my fingertips there is energic quick vibration that I hear but also a slower pumping that i dont hear. 

 Listening more, the experimental nature of Echoes and the whole Meddle album shines through. In other words it may well be that they experimented also in the low frequency range. They used Shepard tones and invented seagull squeals, I read. It is one "flowing" album and the silences between the tracks are not just silence but e g wind blowing too like at the start.So it is maybe a quite special case.

I had significant woofer pumping

https://forum.audiogon.com/discussions/rumble-issues-see-old-thread-update#1559764

Tried everything

then did the feather test

a light feather should be able to move a tone arm

the bearing in my tonearm wasn't moving vertically

all the movement was the cantilever going up and down creating the woofer pumping

Audiotomb - very interesting. I think my arm floats fine but will check when i get home. The HFN record lateral test shows very visible and sonic resonance ca 7hz while the vertical test is much less obvious (the test tone warbles a bit between ca 10 to 5hz).

"If you have rumble problems, get a light feather!" Who said this hobby was boring?

Update: situation in the system at the cottage seems like with the main system at home. Vinyl records including DSD recordings of these made by the same cart-arm-phono-preamp in the main system, create pumping, more or less. Its not just Meddle, but e g Glass and Shankar too and Sade: Love is... When I play digital from the Oppo player I have here - no pumping so far at least, testing SACD Moody Blues: On the threshold, and CD Spirit: Sardonicus.

There is pumping with vinyl but maybe it disturbs less with the smaller speakers and less linear amp here. I also note that there are more energetic vibration from the vinyl (slightly touching the cones) compared to the sacd and cd. My ears tell me I prefer vinyl - this is why i bother to make recordings.