Where do classical vinyl records get their rumble from?
Recently converted back to vinyl from silver disks, I am struck by how much rumble seems to be inherent in the new and used vinyl I am buying.
A case in point, is a recent Deutsche Grammophon (DG) recording (487 7484) of Mahler’s Second Symphony made at a live performance at the Sydney Opera House (I was there). The first set I bought was amongst the dirtiest pressings I have ever had, but the second set was much improved. However, there is a persistent rumble whether played on my Holbo Mk2 air bearing system or my venerable Garrard 301 (new bearing from Classic Turntable Company).
Mahler typically has huge dynamic range, from muted off-stage performers to hundreds of musicians going hell-for-leather.
The rumble could be partly caused by the venue’s air conditioning system, but I hear similar background on a Telarc recording (Stereo 10051) of Saint Saens Organ Symphony made in Philadelphia. Telarc even arranged to have local roads shut down for the recording sessions.
Similar efforts were made by DG when recording the organ at Notre Dame in Paris, where recording was done late at night to reduce traffic noise. My copy includes Dolby Atmos on Pure-Audio Bly-ray (DG 486 1466).
I was beginning to think the rumble was inherent in my tables, but then I played a German Direct Metal Mastered (DMM) set from In-Akustik for Clearaudio’s 40th anniversary (INAK 78051 2LP). It includes some Telarc tracks. This set has the quietest background I’ve never heard. There is virtually no rumble, exonerating my tables.
So apart from the recoding venue’s air conditioning and traffic noise, why do so many classical records seem to have built-in rumble? Could it be from the mastering lathe?
I am really only thinking about classical recordings where the dynamic range approximates the signal to noise ratio of vinyl, meaning that very low-level signals are musically important, while simultaneously bumping against the noise floor.
Rumble can already be “imprinted” into the record itself. This happens if it was created during the original recording,the cutting of the varnish (mastering)or the production of the matrix for printing vinyl. Old audiophiles who listen to vinyl know what I'm talking about. |
I’m an old audiophile, and of my 5000 LPs almost none have any issues with rumble at all. I have one early music record on Argo, and one jazz record on Fantasy with issues, but that’s really about it. The ’imprinted’ rumble thing is exceedingly rare in my experience. I don't even bother ever using the low cut filter on my phono-stage. It's not needed. |
I agree that in general, the record should be in firm contact with the platter. But there are some fine considerations! Hard to know where to start on this one! Garrard was a serious manufacturer in its day, and had a fairly heavy aluminium platter which was die cast, machined to the standards of the day, and finally balanced by drilling small holes. The platter was designed to be easily removed, being seated on the bearing using a Morse taper. If it did not lift straight off, you we told to use a block of wood to tap it loose with your third hand. Like most metal objects, the Garrard platter rings like a bell so it was supplied with a rubber mat. I still have the original mat but it is a bit ragged round the spindle. Now that SME has bought all things Garrard, and is manufacturing new old stock 301s, they have been able to precisely reproduce the mat. However, they will only supply it with their ’new’ 301s which are of course stupendously expensive! I’ve seen prices around US$40,000. What about vibrations emanating from the stylus? I don’t think anybody in the 1960s thought very much about vibrations from the stylus being propagated through the vinyl and reflected back into the stylus, ready to be re-amplified. But this is a focus for many designers these days. The first requirement is a good impedance match between the vinyl record and what it sits on, so vibrations flow into the substrate rather than reflect back. Acrylic is a very close match and is used for platters by several manufacturers, including cost-no-object Wilson Benesch. The Funk Firm Acromat line is made of very stiff acrylic full of tiny bubbles designed to absorb vibration. I bought a 5-mm thick one for the Garrard - and adjusted the tone arm height to suit. The Holbo arrived later. You are correct, it is not supplied with a mat, and the Delrin spindle is short. One of the reviews states that its platter is made of Delrin, which is an easy mistake to make because because the surface is so smooth and black. But Holbo says it is aluminium and anodised. I gradually noticed when playing records on the Holbo that they seemed to pick up clicks (static?) faster than when played on the Garrard / Achromat combination. I moved the 5-mm Achromat across, but the spindle was too short to reliably centre a record and the hefty Holbo puck (630-grams). I don’t know why a metal platter should increase static. Anodising can produce a thick layer of oxide on the surface, potentially 150 microns thick, which would act as an insulator So I bought a 3-mm Achromat for the Holbo which coincidentally arrived in the same timeframe as the DS Audio cartridge. Here I broke a good rule of science. I made two changes at the same time! Now the Achromat came with instructions to stick it to the platter, using six tabs of extremely thin double-sided tape. I had got into the habit of helping the Holbo come to a stop by slowing the puck with my fingers. With the Achromat, this could cause slippage, so I reluctantly stuck it down with the tabs. So now it is no longer a matter of seconds to remove it. The Achromat has a depressed central area to accommodate record labels. The Holbo puck has a recess at its bottom to concentrate down force close to the edge of the label. So short of a vacuum, I think the record and the platter are pretty well coupled. |
@richardbrand interesting… what made the mat a suspect is that you mentioned the rumble had a rhythm to it. That’s consistent with a motor or bearing issue or an uneven surface that creates vibration. Since Holbo uses air bearing and it’s belt driven, the vibrations can ideally only come from the platter/matt. Especially considering that rhythm that you noticed. I would still remove the acrylic mat and try. And just not use the mat or use a thin leather mat. I don’t know…I am always hesitant to add any tweaks to a turntable. Cheap crappy ones can possibly be improved. But something like Holbo no. |
