Strange speeds, big holes, and other answers to vinyl record mysteries: Alan Cross

The surge in vinyl record popularity continues. Getty Images

According to Nielsen SoundScan, more than a million brand new vinyl LPs were sold in Canada last year, up a healthy 27 per cent from 2017. And that number doesn’t include sales through many independent stores, used records, purchases made at record shows or online from sites like eBay and Discogs, and anything an artist may sell off the merch table at the end of a show. Add all that together and the total number of vinyl sales in Canada in 2018 probably exceeded 1.6 million.

With more people getting into the format for the first time and with lapsed fanatics picking up where they left off a couple of decades ago, some people have questions about some of vinyl’s eccentricities. Let’s see if I can help.

Why do records turn at the speeds they do?

Most turntables sold today can accommodate records that rotate at two speeds: 33 1/3 RPM for albums and 45 RPM for 7-inch singles. Why those speeds?

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For the answer, we need to go all the way back to the late 1800s and the introduction of Emile Berliner’s Gramophone (I capitalize that because back then, Gramophone was a brand name, just like Aspirin, Kleenex or Corn Flakes).

Gramophones were manufactured by a number of companies. At some point in the 1890s, an industry handbook of standards was published, decreeing that Gramophone should be equipped with wind-up motors that spun the platters at “about 70 RPM.” No one remembers why that speed was chosen other than the author of the handbook had a machine that operated that way. It became the reference unit.

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By the time we reached the 1920s, turntables (both Gramophones and Edison’s phonograph) were being powered by electric motors which ran at 3600 RPM with a gear ratio of 48:1, bringing the platter speed down very close to 78 RPM (78.26, to be exact).

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The downside of the 78 was that based on its diameter (10 inches), number of grooves per inch (i.e. how tightly packed they could be cut) and the rotational speed, the maximum length of the spiral groove that stored the music was restricted to 270 feet. That works out to about four minutes of music. Not good if you want to listen to an entire symphony with no interruptions.

In 1931, RCA introduced a new type of 12-inch record just as movies with sound were spreading around the world. Motion pictures came on standard reels featuring 1,000 feet of film. Based on the speed that film was fed through a project, each reel provided 11 minutes of viewing.

To match up the film with sound, a company called Vitaphone introduced a system that used a standard 3600 RPM motor to rotate a soundtrack disc. To make the audio last the same 11 minutes, the math dictated that the motor be geared down to 108:1. That gives us a rotational speed of 33.33 RPM.

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RCA tried to introduce the new records to the general public as an alternative to the 78, but it was the Great Depression and the entire recorded music industry saw a sales collapse of 95 per cent through 1930 and 1931. People were not in the mood for a new recorded music format. So in an extremely silly move, RCA let a bunch of patents associated with their 33 1/3 RPM disc expire.

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Fast-forward to 1948. RCA’s rival, Columbia Records, picked up on the technology as they were experimenting with a new plastic substance called polyvinyl chloride — vinyl for short — which had gone into use in the 1920s for sewer pipes.

Vinyl was much more durable than the shellac-based compounds used with 78s. Not only did vinyl last much longer, but the grooves could also be placed much, much closer together and played with a stylus that was tinier and far sharper. These “microgrooves” allowed for a much longer spiral: 1,600 feet. Doing the math (π x 33 1/3 x the outside diameter of the grooves + the inside diameter of the grooves ÷ 2) meant that Columbia could promise up to 24 minutes per side of one of their new “long-playing” records.

RCA was not pleased that Columbia had scooped it with RCA’s own technology and refused to license the 33 1/3 format for its releases. Besides, RCA reasoned, people have been happy with records featuring one song per side for 50 years. Why change it?

The solution was to come up with yet another vinyl format that was seven inches in diameter and spun at 45 RPM.

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Why that speed? Let me stop you if you deduced that 78 minus 33 equals 45. That has nothing to do with anything. We have to look at geometry again and the curvature of the grooves of a record.

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As the stylus gets closer to the middle of a record, the curvature of the grooves increases and its relative speed slows down. Yes, the platter is still turning at 33 1/3 times a minute (1.8 times per second) but the relative speed of the stylus is different depending on where it is on the disc. If it is on the outer edge of the record, it has much longer to go per rotation. But as it spirals towards the centre, more and more information has to be stored per groove per rotation.

The result is an increase in distortion and a loss of high frequencies the closer you get to the middle. This is a major reason why the best songs and the best singles on an album are sequenced toward the outer edge of the disc. They just tend to sound better there.

However, RCA discovered that if it spun a disc at 45 RPM, there was a 35 per cent increase in groove velocity, which greatly reduces the loss of high frequencies and distortion. This does come with a caveat: there’s 35 per cent less space available for music. But RCA thought this was a fine trade-off.

RCA was also an electronics manufacturer. And this brings us to the mystery of the hole.

Why is the hole on a 7-inch single so big?

The standard size for the hole on an LP is 9/32 of an inch. RCA decided to make the hole on its new 45 1.5 inches wide for a couple of reasons.

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First, RCA wanted its new format to crush the LPs being issued by Columbia and its licensed partners. Someone in the company came up with the idea of making and selling turntables designed exclusively for 45s. The thinking was that once people bought one of RCA’s turntables with the special six-inch-tall fat spindle, they were theoretically locked into buying music in the 45 format from then on. Sound familiar?

RCA wanted people to stack records on this spindle so they wouldn’t have to get up and change the record every couple of minutes. Instead, once a record was finished, the tonearm would swing back, the next record would fall onto the platter, and the tonearm would resume playing. It was possible to stack up to about 60 minutes worth of records this way. Take that, Columbia.

But there was a more scientific reason for the larger hole. When a new 45 dropped from the spindle onto the platter, it was required to spin up from a dead stop to 45 RPM almost instantly. The torque applied to the edges of the hole was quite severe and caused standard one-half-inch holes to quickly go out of round, resulting in a wobbly record. Tonearms hate wobbly records.

A larger hole allowed the sudden rotational forces to be distributed over a greater distance (π x 1.5; about 4.712 inches), reducing wear and allowing the hole to stay rounder longer.

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This was especially important for the jukebox industry. In the 1930s, ’40s, and ’50s, jukeboxes were big, big business. Operators couldn’t have popular recordings rendered unplayable by a warped centre hole.

RCA’s plans didn’t work out as it envisioned. Other turntable manufacturers started making machines that spun at 78, 33 1/3 and 45. The Big Hole Problem for regular turntables was solved with a plastic insert that fit within the big hole, making it fit on a standard one-half-inch spindle.

We ended up with an uneasy detente. LPs were designated for “good music,” which was defined as classical, Broadway cast recordings, and jazz. Meanwhile, 45s became the format for popular music. They were cheap to manufacture, cheap to buy, and proved to be the perfect way to send out songs to radio stations.

It just so happens that the rise of the 45 came at exactly the same time as this new thing called “rock ’n’ roll.” In the end, everyone won.

Alan Cross is a broadcaster with 102.1 the Edge and Q107, and a commentator for Global News.

Subscribe to Alan’s Ongoing History of New Music Podcast now on Apple Podcast or Google Play

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