First things first
The Interweb answer to this question is to not record more than 20 minutes on the side of an LP. It’s so nice when you get a simple answer, and you can go about your life with this “complete” knowledge, blissfully unaware of just how abbreviated and generalized that answer is.
Assuming you want to learn more…
First, let's cover a few basics:
The louder the music we record onto a vinyl record is, the larger the grooves are.
Large grooves take up more space on the disk and thus reduce the basic disk space-time limit.
If you lower the level, you can fit more music on a side.
Bass frequencies take up more space on the record than mid and high frequencies.
The way your music is mixed and mastered has a big impact on the duration and level.
Soft records are inferior only because they make it seem like the record noise floor is louder.
A record side that has soft or silent passages can conserve disk space.
Not every lathe cuts a record the same way.
Every cutting engineer makes quality, level, high-frequency and low-frequency judgments differently.
Solving the level-duration-bass riddle
Is this record being made as a novelty piece?
Some of today's record fans don’t even have a turntable. This isn’t entirely a bad thing. It just means that these people will not have any opinion about how the record sounds. And they will not dislike the project if it is cut softly or if it sounds noisy.
Or is this record being made for vinyl connoisseurs? Do you want your fans to get the best analog/vinyl experience? Do you hope important people will hear your record, compare it to other records and write reviews about it?
For the novelty record, disk duration is a minor issue. Long sides are not really a problem. Depending on the music, long sides can be made, and you will have a successful record.
I remember a company years ago (K-Tel) that made compilation records. The entire point of these records was you could get 12 or more of the same genre of songs on a record, and they almost made a sort of party tape vibe. But, as my taste in music and vinyl improved through experience and education (I was in my teens ), I noticed that these K-Tel records and other compilation records were softer, lacked bass and warmth, had more record noise, and didn’t sound as good as the original release.
Why did they sound anemic? To make these compilations have mass appeal, they squeezed several more songs into them. Some of them were nearly 30 minutes long. Acoustic compilations like John Denver’s or Cat Stevens’s music might even exceed 32 minutes. To make these “novelty” records work, the cutting level was lowered dramatically, and the low frequencies were reduced, making them sound thin.
Is this record being made for Audiophiles?
In this case, the duration of 20 mins per side might also be incorrect. To achieve outstanding performance with challenging grooves and other compilations, it might be better to have only 18 minutes per side. Or, if you are aiming for the ultimate performance, choosing to cut at 45 RPM and limiting your side durations to about 12 minutes gives you better high-frequency performance and better overall dynamics and impact.
It’s just not that simple
Many projects are a combination of novelty and high performance. Budgets are limited and don’t always include making 4-sided LPs at 45 rpm. New bands are trying to sound good, but they also know they can not sell their first record at premium prices.
There are other factors that have to be considered when you determine the best level/performance. High-Frequency content may impose a limit on your overall level, or you risk distortion. Changes in dynamics—loud and soft passages—make calculating the ideal level/response a complex task. And wide swings in phase response between the two channels can cause the groove to be too deep.
There are a few mix issues that cause further complications in the cut. But only if you are trying to cut a short side at a loud level. The high-frequency response on the outer portion of the disk is better and more accurate than the grooves closer to the center of the disk. Bright sounds mixed deep into the mix do not distort as easily as the same bright sounds on their own. Sometimes a short side is even more difficult to cut than a long side. All of the above issues get more challenging when we increase the cutting level.
This is where you might look back at the simple answer and say, yeah, let's keep the duration under 20 minutes and call it good. And no one could criticize you for taking that approach.
But if you dare, let’s go deeper into this dilemma. Ride along with me and my co-host, KJ (The Oddysy), as we analyze a few record sides on the new Making Music @ Masterdisk podcast. In the new season, we’ll highlight the issues that actually face a cutting engineer on any given day.
It’s not exactly what you’d expect. So if you want to find out more, stay tuned!