Quoted from Fulltilt:I am assuming because they sound better. Less compression in the grooves at 45 vs 33. Kinda like 15 ips tape sounds better than 7 1/2 ips. Is that basically the rational? They sound incredible.
Thats basically it and you’re on the right track (no pun intended)…primary benefit is that (just like tape) the faster speed reduces the inherent noise-floor.
45rpm also suffers less ‘diameter loss’ which is the phenomenon of how as your stylus tracks closer to the center of the disc is reproduces exponentially less treble due to the groove structure being more tightly packed* as it relates to physical geometric shape.
* I tend to not use the word ‘compressed’ when describing this because it too often gets associated with ‘dynamic range compression’ which is not the case here. But in the true sense of the word, yes…the grooves are being physically pushed closer together at the inner diameter than the start of the disc.
On a 12” disc you essentially have 3 inches of usable land for the cut. Most of the time people are trying to cram way too many songs/too much time and exceed the specs of the format. For example, yesterday I cut an LP that had over 24 minutes on the A side. In order to fit this much time you have to cut in a way the relaxes the groove structure so that the lathe will pack them as close together as possible…the main way to do this by reducing the volume of the cut which equates to more audible noise floor on playback. If you took that same side and spread it across two sides (so now 12min per side) at 45rpm you now have double the physical space to cut, which means a louder cut with lower noise floor = happy audiophiles!