Where do classical vinyl records get their rumble from?

@lewm 

RB was questioning the frequency at which compliance is ’measured for one of his cartridges.  The correct answer cannot be "1kHz, 5cm/sec".  Raul answered RB’s question

Thanks for coming to the rescue!

Raul gave 65% as the relative difference between 100-Hz and 10-Hz, but the only compliance number I have found so far for DS Audio is at 125-Hz.

This is all rather academic because of recommendations from other users and manufacturers about what works well.  Calculations only go so far.

In other threads, I have argued about what the effective horizontal mass of the Holbo tangential arm is, concluding it must be the entire mass of the tonearm assembly that moves sideways.  For me, that works with static compliance.

But most of the tonearm's 31.6 gram mass is probably concentrated in its bearing, 6" away from the cartridge and connected to it via a rigid 1/4" tube of aluminium/carbon construction.  When dynamic side loadings are applied at say 10-Hz or 100-Hz, I would expect the arm itself to flex slightly, absorbing some of the side motion and making the effective mass less than 31.6.

What do you think?  This is for my academic interest only ...

I got my second hand RXR rack with shelves in 2019 for 5.5k. Nowadays prices much higher.

HRS and CMS seem to have the best isolation, but is pricey. Wood is a good positive alternative, maple being a favorite amongst some. Otherwise, it’s difficult to sort through the myriad of footers to find an ideal option. 

Your Holbo is a great high-value sonic buy. I picked up a used VPI Avenger rim drive with 2 VPI arms for 8k. I picked a multi arm to run a variety of cartridges including mono and SPUs. I’ve since upgraded the tonearms.

@stievus

If these recordings give you rumble as you describe, then it must be your deck. (My humble opinion...) I am still using a Pink Triangle Export Gti

I have a number of exceptionally quiet records, some listed above, which in my opinion exonerates my decks.

I have thought about it some more, and two of the records I mentioned as noisy were not recorded in purpose-built studios. For one recording, local streets were shut down to reduce traffic noise, but obviously there is a limit to restricting noise in a big city.  Another contributor mentioned hearing London tube trains on records.

Big cities are inherently noisy, though usually quieter at night.  I was camped south of Sydney, and in the middle of the night became aware of very faint, periodic subterranean rumblings, each lasting about a minute.  Turned out it was the sound of underground coal mining machines, being transmitted through kilometers of solid rock.  The machines are so-called "continuous miners" but they stop to unload when they have chewed about 100-tons, in order to unload.  Hence the minute duration!

That and the London underground got me thinking about the Sydney Opera House where the live recording of Mahler 2 was made.  It has to contend with trains and traffic on the Harbour Bridge, plus constant ferry movements, the occasional cruise liner being moored, a double-helix underground carpark, freeways, helicopters, etc.

Around the time the recording was made, massive Tunnel Boring Machines were boring under the harbour.  Against this backdrop, the venue is amazingly quiet but to very sensitive microphone?

By the way, the Achromat platter mats I use are directly descended from Pink Triangle which is one of the reasons I got them!

@kennyc 

Obviously value depends on the exchange rate.  Two Holbos could be very cost-effective for alternate cartridges, unless you need removable head-shells!

Just a thought ...