Why are my woofers pumping?

Dear friends

Atmasphere, VPI - if the pumping repeats once per revolution, how do you know it is the drive / turntable, and not the record itself?

As shown above - the evidence in my case points to the vinyl. E g the pumping varies from record to record. It would not have done so, if it was due to the turntable. And a number of turntable fixes have no effect. AND vinyl recordings made on my former HW-19 turntable seems to pump the same way! The main suspect is the cart-arm combo.

I hope to test this, with a different (lower compliance) cart, in some weeks time, and will report back.

Clearthink - I do want to resolve the problem! I agree with your line of thinking - I also thought it was a two-component problem (low resonance plus something - possibly a turntable issue) - but recent testing seems to show that this is wrong. It is basically a one component problem - the resonance. I’ve tried a lot of remedies, so far. The turntable is not the main suspect. Please folks, read up on the Hanss T30 players. Not where you would look for rumble (and I have tried).

Analogluvr - good idea. I can vary the phono stage volume (it has volume controls). Basically, up to a point, the more the Aesthetix phono stage takes care of the gain, the better the sound. The sound is fine with the Einstein preamp also, but still, it is a step down (the sound is more slim, solid state, compared to the fat, organic Aesthetix). The best fit, in my system, is ca two thirds Aesthetix, one third Einstein gain, before the signal is fed to the amps.

I tested a bit - Pink Floyd: Echoes, once more - changing relative gain levels. Result: much the same woofer behavior, regardless of the phono stage / preamp mix. Like you write, maybe turning down the Aesthetix "alleviates" the problem, but this is marginal. Basic conclusion, the amount of gain phono stage vs preamp is not a decisive factor.

Once more I note that the woofer pumping varies with the LP. Example: I put on my UK original of Colloseum: Those who are about to die, expecting pumping, but there is little, despite very energetic woofer movement within the music tracks. Is there, still, a part-subsonic rumble, due to the low resonance, disturbing the sound? I don’t know, but it is not very obvious. The bass on this LP seems limited (compared to Pink Floyd Meddle, made ten years after). The problems I hear with the sound seem to relate to the treble, not the bass.

My system has "distributed" bass reproduction. It is not a full Audiokinesis "Swarm" bass system, but goes part of the way, with four speakers reproducing the bass. These can be aligned in the analog domain by positioning and other measures. This sounds better than any form of digital equalization I have heard so far. I had a Velodyne DD-18, but sold it.

@o_holter  Well, I don't know it is the TT as opposed to a warped or otherwise flawed LP.  If the pumping is being caused by the record I can think of only 2 issues: 1) The records are warped or otherwise flawed and you're not going to solve that problem by making changes to your system; or 2) Your system is so resolving at subsonic levels that it is reproducing subsonics that were present at the recording venue.  Once again the problem would not be your system.  I don't recall the LP but I have one where I can actually hear either a subway or air conditioning system on the record.  

Since, however, you have mentioned several times that the pumping occurs one time for each revolution of the LP it would seem an amazing coincidence for you to have that many warped records or that the signal recorded on the master was exactly in sync with one revolution of your platter.

Thank you, vpi. I have no indication that the pumping happens only with flawed or warped records. I think your hypothesis 2) is correct, that is, first the low resonance plus a superb cart picks up subsonics, and next, the system is very resolving and sends it all to the speakers. Note, however, that even my modest cottage system was able to reproduce the pumping.

I don't have test instruments to test if the pumping is exactly in sync. I can only say that the pattern repeats ca once per revolution. This is easiest to test in the outro of a record with pumping. There is a click once per revolution when the lead-out groove meets the circular groove at the end, and I can see (and touch) the woofers pump in a regular pattern between each click. So it seems roughly in sync. Which would be the case with most records I would guess? 

Examples of records with subsonic woofer pumping:Pink Floyd Meddle (UK orig), Rickie Lee Jones: Evening of the best day of my life, Byrds: Untitled (US orig), Byrds: The Columbia hits (Sundazed).