Low Frequency Rumble Question

Many of the RCA records recorded in England (for example, the Faust/Carmen or Royal Ballet Gala records), like their Decca counterparts, have glorious reproduction of the London Underground going by under the hall in which the recording took place; the Heifetz recordings often have a low frequency content that may be someone moving around on the podium(?)--for example, the Bruch Scottish Fantasy. On my Shaded Dog of the latter there is no problem, but Classic's records have much better bass extension, which in many cases is a mixed blessing. That may be what you're hearing, assuming your speakers can get into those nether reaches. Ah, wish my pre had a rumble filter!

Jackcob, what records specifically are causing this rumble? That will give a clue. Like I said before, the Underground's rumblings are clearly audible on the British RCAs, throughout the recordings, and Classic's reissues are good enough to capture them (that's one of the reasons Carnegie Hall and Trinity Church in NYC are not favored recording sites, good as their acoustics might be, as the subways are clearly audible, and felt, in those places). Only other alternative I can figure is whether the records have any warps.

By the way, there's a story as to one of the London halls which was an excellent recording venue until an Oriental rug dealer went out of business--he stored his rugs under the main floor, and when they were liquidated their damping effect on the Underground was lost, making it impossible to record there without too much interference from the trains.