Disk records have been around for a while, long before they reached their vinyl form. Since then, vinyl records have been available in different sizes and profiles.
During the mass-manufacturing process, vinyl records are pressed into shape from a “puck” of extruded PVC, using a steam-heated hydraulic press. The exact profile of the records is given by the two stampers, or molds, fitted to the press, on which the two stampers are mounted, one for each side of the record. The final product is trimmed to remove the “flash,” or excess material sneaking out from between the molds. (For a brief explanation of the process, click here. You can also refer to my articles in Copper Issues 92, 93 and 94.
For many decades, the big quest in this sector of manufacturing was to figure out how to optimize the pressing cycle, process parameters, mold geometry and PVC compound, in order to make the thinnest record possible in the shortest possible time without introducing negative side effects. Given that during its heyday the vinyl record was the best-selling consumer medium, the savings in PVC during large manufacturing runs were considerable and the ability to pump out more records per shift would maximize profit.
Some record industry insiders would therefore consider the thinnest records to offer the best value and the machines capable of manufacturing them quickly as representing the epitome of quality.
Nowadays, however, it is the thick, heavyweight 180-gram pressings that are regarded as the better quality item.
But, are 180-gram records really better?
Do They Have Deeper Grooves?
One popular misconception is that thicker records must have deeper grooves. They don’t. Groove depth is set during the cutting of the master lacquer disks and is ultimately limited by the thickness of the lacquer coating on the aluminum substrate on these disks. Every lacquer master disk ever made has had a very similar coating thickness, so there was no way to cut deeper grooves.
The maximum groove depth that can be cut on a lacquer master disk is nowhere near deep enough to even remotely approach producing a corresponding groove in the final vinyl disk that would be deep enough to break through to the other side of the record. Because of this fact, even on the thinnest records ever made, the thickness of the final product (the pressed vinyl record) never imposed any limits on possible groove depth.
In fact, even if it were possible to cut deeper grooves than permitted by existing lacquer master disks, the playback cartridge cantilever would most likely bottom out long before the grooves on the opposite side of the record were disturbed by excessive depth. Moreover, the maximum permissible groove depth for playback cartridge compatibility, as defined by the standards documents pertaining to record manufacturing, is much less than the maximum depth possible on lacquer disks. Therefore, in practice, lacquer disks are not the limiting factor either.
Moreover, the vast majority of records available are not even close to using up the maximum groove depth permissible. Deeper grooves do offer sonic advantages, up to a certain point, as long as they remain compatible with available playback cartridges. But most records in existence have shallower grooves than what would offer the best sound quality.
This is primarily due to the fact that deeper grooves are also wider, and as such, they take up more real estate on the record surface, which greatly reduces the playing time per side of the record. Mainstream record labels have traditionally preferred marketing over sound quality and the buying public was generally assumed to be morons who didn’t know any better and were not able to hear the difference in sound quality, but wanted to feel that they were getting more music for their money. Audiophiles aside, this assumption was sadly a rather accurate observation of market trends.
Also, a double LP of excellent sound quality is much more expensive to produce than a single LP with double the duration per side and much inferior sound quality. But the single LP would sell better, to an audience that was indeed mostly oblivious to sound quality concerns anyway. The single-LP version would necessarily need to have much shallower grooves and perhaps much more restricted low frequencies and dynamics, along with a poorer signal-to-noise ratio.
Yet, from the late 1950s up to the late 1980s, when disk mastering equipment manufacturers went back to only manufacturing truly profitable items such as guided-missile systems and microphones, the main focus of this industry was how to fit more playing time per side of a record. A glance through the relevant research papers from this 30-year period reveals that improving sound quality was not among the research questions. Increased playing time, loudness and automation to eliminate the need for too much skill in the mastering process (highly skilled and potentially irreplaceable reasonably-paid professionals were already becoming unfashionable back then), were what everyone in the record-manufacturing business was after. Which is how a small niche market, predominantly concerned with sound quality, developed in parallel, but this is a different story for another issue.
Deeper grooves also wear out the cutting stylus faster, so the lower-priced disk mastering services prefer keeping their expenses to a minimum by cutting shallower grooves and keeping the stylus in use longer.
So, why did the industry go back to making thicker records if it wasn’t for being able to support deeper grooves?
Are They Flatter?
Some claim that 180-gram pressings are flatter. But, in fact, thicker records need more time to cool, which is one of the most important stages for creating a flat record. The vast majority of pressing plants nowadays are very unlikely to put more time into the process, apart from the very few facilities that specialize in quality (at a premium that mainstream record labels are guaranteed not to want to pay).
So, in practice, thinner records are more likely to leave the factory in a flat state than thick ones.
Thicker records that have not been allowed adequate cooling time are not going to be flat to begin with and they certainly won’t be getting any better after leaving the factory.
Once a record leaves the factory, it is subjected to mishandling, extreme temperatures, improper storage and the retail environment, before reaching the safety of the home of a caring collector. Even if a record leaves the factory perfectly flat, it is very uncertain if it will remain as flat for long. Thicker records may prove a bit more durable, if they are made with due care to begin with, so they may have better chances of surviving the journey from the factory to the buyer’s home. This may be the only valid technical advantage of 180-gram records, yet it is not often found in the marketing hype.
Better Playback Angle Geometry?
Another question is whether the slight difference in record thickness would raise the playback cartridge enough (less than 0.5 mm?) to materially change the vertical tracking angle (VTA), stylus rake angle (SRA) or tonearm statics (the fact that a sloping structure behaves differently in a dynamic environment than the same structure without the slope, and there’s at least nine inches from the tonearm pivot to the stylus tip). The difference in angle created by a thicker record can be calculated and it is small. Is it audible? Well, the same lacquer master disk can be used to produce stampers to be used on two different presses, one pressing thin records and the other one pressing thick ones. The difference would be small, if audible at all; in my experience, much smaller than the difference between records of the same weight and thickness pressed using a different PVC compound (as would happen when stampers produced from the same lacquer masters are sent to different pressing plants in different countries; for example, for an international release).
The difference in sound between different PVC compounds is due to the elastic deformation effects of the record yielding under the playback stylus tip. Different PVC compounds produce records having different physical properties. In theory, any change in material thickness would also change the physical properties, but in most practical cases, the effects of the platter mat resilience will most probably dominate the resonant behavior of such a system to a much greater extent than a 0.5mm thickness change. The audio experimenter preparing to discover and document PVC compound and record thickness effects had better be prepared to begin with a massively rigid, non-ringing platter that does not require a resilient mat.
Despite all of the above, the main selling point of 180-gram records has more to do with human psychology than anything related to sound or music: a heavier object better serves to fulfill that fundamental human need to feel that you are getting more for your money. In this case, more plastic.
Buying records essentially boils down to the simple fact that it is something we enjoy. It makes us feel good. If buying a 180-gram record makes you feel better than having a lighter one, then there is no reason not to go for it.
Finally, there can be no harm in a record being heavier than it needs to be. At least, until you decide to move and feel safer carrying your prized record collection yourself, at which point you will probably explain to your physiotherapist that perhaps thinner records are fine after all…!
Header image courtesy of Wikimedia Commons/Ryankusumojr.
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