Where do classical vinyl records get their rumble from?

@richardbrand I have about 7,000 LPs and don't have rumble issues on them except for the very few LPs recorded at Kingsway Hall under which a subway ran. Those LPs are famous for that (mostly EMI).

I have stayed mostly away from DG recordings since their microphone technique seemed inferior to me as compared to Decca, EMI, Mercury or RCA. They have done a few that are quite good though. I do not regard Archive as part of that mic placement issue.

But no rumble. My main speakers are flat to 20Hz as are my subs (used to break up standing waves in my room). The phono section cuts off at about 2Hz. My arm and cartridge match pretty well so the mechanical resonance falls within the recommended 7-12Hz window. If the mechanical resonance is outside that window you can encounter problems with low frequencies!

You've mentioned the use of a turntable with an air bearing. This is entirely the FWIW Dept.: There should be zero slop between the platter surface and the mounting of the cartridge. As best I can make out, air bearings do not satisfy that requirement. The more slop there is, the more difficulty involved getting the cartridge to track properly and not pick up artifacts from the turntable itself. An air bearing for a platter can oscillate up and down (there might be a means of stabilizing that of which I am unaware...). Any microscopic movement in that regard can be interpreted by the cartridge as a signal. 

Idler drive turntables are also known for lessor rumble noise floors. It is why there are belt and direct drive turntables. 

As yet I'm unconvinced that your LPs are the problem. Your surmise that classical is the most demanding in terms of surface noise is also incorrect. There are many non-classical recordings that are just as demanding of the noise floor of the LP. FWIW, I ran an LP mastering operation for about 20 years. Mastering lathes of course generate some rumble too, but the savvy operator of such devices knows to run the lathe for 20-30 minutes to warm up the bearings (if an older style lathe, such as the Scully we ran). I think we can rule out the mastering lathe since they do any and all recordings made though. 

Richard…I didn’t see if you tried 
1. Removing all platter mats 

2.Listened to the same problem recordings on CD/SACD/Streaming to check in that pesky rumble 

If yes, what were the results?

Im in the camp that guesses your TTS are the issue. 

And Richard….Do you hear the rumble through headphones if you have that option?

I agree with the replies the that there is nothing inherently more prone to rumble in classical recordings 

@chrisoshea 

I agree with the replies the that there is nothing inherently more prone to rumble in classical recordings

No, rumble (whether from table or record) is just more noticeable because of the huge dynamic range in some classical music, especially large-scale romantic orchestral / choral works.  When the music is very quiet, it is on a collision course with the noise floor of your gear.  To those who cannot hear the noise floor, turn your volume up until you can.

@chrisoshea 

Im in the camp that guesses your TTS are the issue

How then do you explain how some records exhibit significant rumble-like noise while others are nearly silent, when played on the same turntables?