Why are my woofers pumping?

O_holter: Sorry I misunderstood you, conerning the bump during cd playback.  Since it's only when playing vinyl, common sense dictates it has to be in your TT.  Too bad u don't know someone who could bring their TT over for an A/B comparison.  Good luck. I'll be very interested to know what u find.                                                 Steve in Tennessee. 

@o_holter , if its happening once per revolution regardless of the LP, its a defect in the turntable. Could be a bad bearing (which is why I specified grease earlier, rather than oil), could be something that rubs on the platter or it could be the platter out of balance, and shifting on its spindle as it rotates.

The preamp is clearly off the hook. To test this I would simply borrow a turntable, it does not have to be expensive, just to try out.

Thank you for your patience and help my friends.

Handymann - hire an exorcist – indeed !! I played Crime of the century (Mofi version). Woofer pumping between tracks – yes, some. Much energetic woofer vibration in the loud parts of the music - yes. But it sounds great. You said the Fathom subs “didn’t like it”, what happened?

Atmasphere - the pumping seems to repeat very exactly once per revolution – yes. But why does that point to the turntable, rather than the vinyl? My suspicion is that I pick up vinyl noise. That’s why it varies between records, and why I see it also on recordings made on my former VPI turntable. And why tightening the spindle housing and oiling the spindle made no difference.

So yes, I have a main suspect, so far – the low or borderline low cart-arm-resonance, around 7 or 7.5 hz. I will have to check with a lower compliance cartridge, when I get the chance. I borrowed an Ortofon Cadenza Black a year ago. At that time I was not much aware of the pumping problem (maybe, it was less prominent), but I remember that I felt the sound was more polite, less grunt in the bass, compared to the Atlas (the data of the Cadenza, combined with the SME V, suggests a resonance around 8.5 hz).

Raul – try another phono stage - good suggestion. Maybe the “borderline problematic” resonance interacts with some other factor, like an over-eager phone stage (or some non-optimal tubes in it). I will test with my ASR Mini Basic phono stage, solid state, very decent sounding. I bought it since the Aesthetix Io was a long time gone for repair. But when the Aesthetix came back, the reaction over here was just WOW. So if the ASR pumps less, it is maybe because it is more anemic or polite. The Aesthetix is known for its explosive dynamics and it goes down real deep. I will check.

All in all, I am learning to live with the problem...enjoying the music, but also, not giving up, the mystery will be solved. Music mainly sounds great. There are no “obvious” signs of rumble. I have a suspicion that the subsonic pumping I see between tracks has a negative effect on the music, but I don’t know this. If it had been really bad I would have preferred playing digital, but I don’t.

A final observation. The pumping is more visible in the right than in the left channel (in my home system, at least – not sure about the cottage system). No idea why.

Where in Norway do you live, o_holter? If you live in, or close to, Bergen, I can lend you a Soundsmith-modified Denon DL 103 R to test out your theory. It should certainly be low-compliance enough.

Thanks tkr - but I live in Oslo.Thinking about the problem, I thought: maybe it is related to the Telefunken NOS tubes I use in the super sensitive first gain stage of the Aesthetix Io. So I pulled it halfway out of the shelf, enough to get off the top, and swapped the two Telefunkens in the right channel for a new pair of PSVANE 12ax7. Result? No difference. The pumping is still more visible in the right than the left channel. Then I swapped the left and right phono cables leading to the Io. Again: no difference. Right channel pumps more.