Why do 45 records have a big center hole?

The linear velocity of the outer grooves of an LP is roughly 25% faster than that of the outer grooves of a 45. As they both track towards the centre the 45 ends up about 35% faster than the LP.

The choice of speeds is messy, as it relates to both frequency response and also the level the recording is cut at. As the groove wiggles, a loud component requires a bigger wiggle, but the geometry of the system places an upper limit on the angle of the wiggle - too steep an angle and you will end up with problems that will result in distortion or mistracking. So, within a defined frequency range and dynamic range, there is a trade-off between the level you can cut the disk at, and the speed of the groove. Also, a higher cutting level means you need to space the grooves further apart. (There is the complication of the RIAA response, which boosts high frequencies and drops bass frequencies when the disk is cut, and does the reverse when played - in order to preserve the higher frequencies which would otherwise be lost in the noise, and stop the bass frequencies causing a groove that was insanely wide. But this standard is the same for all 45s and LPs, so it doesn’t make any different when comparing them.)

For your standard radio play single, a 45 works well. You get a reasonable groove speed, and you typically don’t have a lot of music to put on the disk, so you can exploit that groove velocity and cut the recording at a higher than standard level. This gets you a recording that is slightly louder, but also has better signal to noise, and lower distortion. That allows the mix to exploit wider dynamics. (There is some irony here, the radio stations will run your carefully crafted high dynamic recording straight into a compressor, and to some extent undo a lot of what has been achieved. There was a certain level of arms race here, with the creation of special mixes designed to sound good when played by a radio station, and special releases of these disk only to the radio stations. They were not actually designed to sound right on a domestic system.)

Once you start to pack longer recordings onto the disk you need to back off the recording level to narrow the effective space taken up by the grooves. If you have a much longer recording you can back off the level to lower than standard, and pay the price with a slightly softer level, and slightly worse signal to noise.

The top end of the dynamic capability is of course the 45rpm 12inch. With only a couple of tracks (I remember when you got the standard track plus the “radio mix” or “dance mix”). The really high groove speed at the outer edge of a 45rpm 12" allowed a very aggressive recording level, which allowed serious dynamic range.

Interesting. I know that in Cecil’s column it says that “The slower a record revolves, the longer it plays and the worse it sounds.” But later on it does say that technology caught up such that 33 1/3 RPM sounded as good as the old 78s. I wonder where the break point is…that is, could you do 16 RPM without severely compromising quality?

16 rpm was produced in small amounts, but strictly for “talking books” for the blind or speech recordings.
One of the reasons 78s required such high speeds to sound decent was they were made of such poor materials. 78s were typically made of a patchwork of shellac, clay, carbon black, and fillers. That meant tons of surface noise. Vinyl had much less surface noise.

In his first Imponderables book, David Feldman wrote, “The only reason 45s still keep the big hole in the 1980s is so they won’t render current jukeboxes obsolete.”

Well, of course, that happened anyway.

I guess now it’s so you can tell a 45 from a 78 without having to read the label.

Well, that and the records themselves being completely different sizes.

LPs actually sounded better than 78s. The main reason was the smaller stylus and groove size. The grooves on 78s were about 3.0 mils, while LPs started at 1.0 mil and later went to 0.7 mil. A wide stylus has a hard time tracking high frequencies due to the small size of the undulations.

Consider the outer edge of a 10-inch 78 versus the outer edge of a 12-inch LP. The linear speed of the 78 groove is about 41 inches per second, while that of the LP is about 21 inches per second. It seems that the 78 has a definite advantage. But with a groove size of .003 inches, the 78 speed is about 13,666 groove widths per second, while an LP with a groove size of .001 inches has a speed of about 21,000 groove widths per second. An LP with a groove size of .0007 inches has a speed of about 30,000 groove widths per second.

So an LP, even though it has a slower rotational speed, is better able to reproduce high frequencies than a 78 can. There are other reasons that LPs sound better - proper tracking is easier with a lower groove speed, for example.

As for 16 RPM records - they will definitely sound worse than 33s. At that speed I would expect the top-end frequency response to be about the same as with 78s. The 16 RPM speed was used for spoken books for the blind, where the convenience of having each side last twice as long outweighed the loss of fidelity (which wasn’t enough to hurt the comprehensibility of spoken material).

Whilst lps might have sounded better on certain levels, they did not have the dynamic range of 78s, but that should be no real surprise given the groove speed.

78s RnR records always sounded more lively than the 45 or lp recordings.

If you have something around that’ll spin a 78, try it, although the background noise will be poor you will notice the sound is very lively - unless its been played to death