Why Do Some of My 33 RPM LP Records Play Longer Than Others?

Have you ever noticed that one of your 33 RPM LP records plays for a much longer duration on each side compared to your other records? While this may seem puzzling at first, there are several factors that influence the length of the audio on an LP. Here’s a delve into the reasons behind this phenomenon.

The Role of Loud Passages in Groove Spacing

The length of playtime on an LP record primarily depends on the number and intensity of loud passages in the music. If the music contains fewer loud passages or is heavily compressed, the mastering engineer can maintain closer groove spacing during the mastering process. In contrast, for music with more dynamic range or more frequent loud passages, the groove spacing tends to be more extensive. The mastering engineer relies on a signal preview to set the groove spacing accurately, allowing for either close or distant spacing to accommodate different music characteristics.

Regional Differences and Record Manufacturing

The location of production can also contribute to the varying playtime of LP records. In the United Kingdom, records were often packed with a greater amount of music compared to their American counterparts. For example, The Beatles' albums had 12 songs on each LP in the UK, whereas the American versions typically had only 10 songs, a practice that continued into the release of Sgt. Pepper's Lonely Hearts Club Band. This discrepancy in playtime provides a clue about the potential differences in your records.

The Engineer's Preference for Distance from the Label

The position of the label on the LP also plays a role in the groove spacing. Engineers often preferred to avoid getting too close to the center of the record where the label would be placed. This preference occasionally resulted in some albums or 45 RPM records having grooves that were closer to the edge of the disc, thereby extending the playtime by a few seconds.

Mastering and Groove Spacing

Mastering is a crucial step in preparing the final audio for release. If a record is mastered at a lower volume, it can significantly affect the grooves and the overall audio fidelity. Standard LP playtime is approximately 22 minutes, but if you find an LP that extends beyond this, it is likely that it was mastered at a lower level. This lower mastering level can result in less fidelity and more noise due to the narrower grooves. The bass volume, in particular, takes up more groove width, requiring the lathe to be set for a closer tracked cut by reducing overall volume or bass. Reducing the volume to achieve a narrower pitch track cut also lowers the signal-to-noise ratio, adding to the noise floor.

Characteristics of Long-Playing Records

If one of your records indeed plays longer than expected, it is likely to exhibit specific characteristics:

Relatively few instruments playing low frequencies, allowing for narrower grooves and more turns per side. Music with fewer percussive elements and more slow, washy string pads, which have fewer transients and thus require narrower grooves. A generally softer volume throughout, leading to narrower grooves and more turns per side.

Conversely, if the record does not exhibit these traits, it is probable that it sounds awful due to the technical limitations of packing enough low-frequency content, transient content, and high volume within the constraints of the LP format, which is typically around 24 minutes per side, often pushing the limits.

Understanding these factors can help you appreciate the craftsmanship and decision-making that goes into LP mastering and production. Whether your record plays longer or shorter, exploring its characteristics can provide insights into the art and science of vinyl recording.