Why are my woofers pumping?

@o_holter

It sounds as though your setup adjustments might have reduced some cartidge resonance. I’m thinking that was likely part of the problem.

And in answer to one of your questions, yes, sometimes subsonic noise is actually pressed right into the grooves. It can result from multiple steps of the vinyl manufacturing process. It can also result from warps but that is a problem more often associated with stable balance tonearms, such as some uni-pivots, as their tracking force changes when they traverse the warps.

So there’s many factors that can lead to woofer pumping, but only one ironclad solution: a rumble filter. It will only be a detriment to the sound if that is your expectation. For every one who claims they alter the sound, there’s probably a dozen who claim otherwise.

I own the KAB Rumble Filter and I am one of the ones that claim otherwise.  (No change in the sound!)

@o_holter : Again:

https://forum.audiogon.com/discussions/why-are-my-woofers-pumping/post?postid=1551771#1551771

With all respect to those gentlemans that insist on the KAB filter or the like please ask you: who of them owns the Atlas or even listen that kind of very high quality performance levels?

Seems to me that no one of them because they are not taking in count what really means: quality level performance at the Atlas levels- They say that with the filter they almost did not listen degradation and this just makes no sense.

R.

Almarg 4-24-2018
... given the unusual design of the turntable’s drive mechanism (comprising six belts, three of them driven by what is apparently a synchronous motor on one side of the table, and three of them driven at a different height by a similar motor on the other side of the table) ... the platter might be being driven in a slightly uneven and/or not perfectly level manner. Perhaps simply due to the condition of the drive belts differing slightly between the two sides.

And I note from your system description thread that the table appears to be around five years old. Perhaps all that is needed to resolve the problem is a new set of belts?


Cleeds 4-28-2018
That actually sounds very much like a drive problem, such as a bearing issue or bad belt.


Atmasphere 4-30-2018
Boy, that sure sounds like a drive issue to me!

Consider replacing the belts!

Best regards,
-- Al

Correction: the Atlas has a 121 ohm load (not 100) - and sounds fine.
Replacing belts - yes, new ones ordered.
I will give the spindle a drop of oil, and fasten the spindle housing when I get the right tool.
BTW, reading up on the Hifi News test record shows that people find a lot of problems with it. On the lateral resonance test the actual test tones are different from those stated. I know from before that the record's anti-skating test is not good, in my case at least.
Some years ago Michael Fremer reviewed the Kuzma 4-point with his Lyra Titan i cartridge, pronouncing it the best arm he had heard so far. But using the calculators, resonance is down to ca 7.2 hz. Even more problematic than with the SME V (ca 7.5), since the 4-point weighs a bit more. Yet it wasn't a problem, to his ears.