Yes, the groove still slows down as it moves inward, but the effects are greatly reduced. This gives you a 35% increase in groove velocity at any point on the disk, which is a huge advantage. The best solution is to make the record short enough to keep the music away from the very end of the disk, but when you're pressing an LP, that's hard to do.Ī better approach is to spin the disk at 45 instead of 33-1/3 rpm. In addition, using an elliptical or line-contact stylus that has a smaller tip radius will help. To get around this, one approach is to keep the recorded volume to a reasonable level. The problems start when the curvature of the groove equals or exceeds the diameter of the playback stylus. The result is actually a loss in high frequencies - an increase in distortion as the groove moves to the center. That 1.8 seconds at a 12” diameter is covering a lot more territory than at the minimum 4.75” diameter. The record is still turning at 33-1/3 rpm, but one revolution takes 1.8 seconds. Curvature isn’t usually a problem, near the outside edge of a 12” 33 1/3 record, but as the groove moves toward the center, its relative speed slows and curvature increases. In record mastering, the higher the recorded level and frequency, the greater the curvature of the grooves that get created when making master plates. Issues of Platter Size and Rotation Speed The 33-1/3 rpm, 12-inch format developed by Columbia was a compromise that attempted to fit more music on a single disc, accepting the limitations that will be discussed in this section on sound quality. Given vinyl groove dimensions and certain assumptions about bandwidth and tolerable distortion, a speed of 45 RPM came out of the formula. That's why a 7-inch single has a label 3 1/2 inches in diameter. Calculations showed that the optimum use of a disc record of constant rotational speed occurs when the innermost recorded diameter is half the outermost recorded diameter. The 45 RPM speed is the only one to be decided by a precise optimization procedure (by RCA Victor in 1948). ☞ Our " Sound Gallery" contains examples of the superior audio you can get from 45s, comparing them to the LP versions. Most of this material comes from companies that master records for a living and was used to explain to customers the differences between 7-inch and 12-inch records and between 45 RPM and 33-1/3 rpm speeds. The distance from the record's edge to its center, and the shape and configuration of the record's grooves play their part as well. As the discussion will make clear, speed isn't the only factor that comes into play. This page explains why music simply sounds better when mastered to 45 RPM than to 33-1/3 rpm, and the simple answer is that more of the original music is preserved at that speed. Presumably, it is powered by the spinning 33 RPM platter, and gears this down to 16 RPM for the record placed on top.When using a master tape to create records, one of the primary goals is to preserve as much of the audio as possible. While the mechanical details are not explained, it allows a 16 RPM record to be played on a 33 RPM turntable. The article does include an interesting adapter, shown here. Eventually, curiosity got the better of me, and I checked out a 16 RPM talking book from the library, just so that I could play it at home. If you search eBay today for 16 RPM records, the most common search result is this talking Bible.Īs a kid, my record player had the setting for 16 RPM. The format was used mostly for “talking books.” The best seller was probably the Bible, which was recorded in the early 1950’s at the lower speed. At the time, the maximum frequency response went only to about 9000 Hz. But the article noted that the speed, while longer playing, had inherently lower fidelity than higher speeds. Most notably, some records were produced for the benefit of Chrysler’s Hiway Hi-Fi experiment, which included a record player for the car. The 1957 article predicted, erroneously it turns out, that “the growing catalog of recorded material and new playback equipment in all price ranges proclaim that the tide may yet turn to 16 rpm and roll into the arena with quite a splash.”Ī few musical recordings were issued on 16 RPM. More precisely, the records played at 16-2/3 revolutions per minute, and most moderately priced phonographs in the 1960’s would play the speed, along with the more common 33, 45, and 78 RPM speeds. Sixty years ago, the August 1957 issue of Popular Electronics carried an article about the forgotten stepchild of audio recording: The 16 RPM record.
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