Why recordings made before 1965 sound better.

Dolby was for TAPES, particularly Cassette Tapes, NOT LPs.

And, prior to improvements in tape formulations and tape mechanisms.

All Tapes make Hiss, and Dolby B was developed for the noisiest: small 1/8" wide Cassette Tapes, running at very slow 1-7/8" IPS.

The narrower the track (less magnetic material) and/or the slower the speed (also less magnetic material), the higher amount of noise i.e. Signal to Noise Ratio!!!

Master Example: 1" wide 30 IPS. Some used 35mm 1-3/8" wide.

Cassettes were originally made for dictation, they ran 1 mono track one direction at 1-7/8 IPS. Then manually reverse, 2 mono tracks at 1-7/8 IPS.

Next: 2 forward tracks: Stereo; and then 4 even narrower tracks on 1/8" wide tape two forward and two reverse, still only 1-7/8 IPS.

Next, auto reverse, and either a 2 track head that spun around, or separate forward and separate reverse heads.

A piece of crap format to begin with, made acceptable, and even better than that by all subsequent advances, and the ability to make your own tapes was a genuine treat. Dual decks, dubbing, OMG the freedom was intoxicating.

similarly 8 track cartridges, before cassettes, the ultimate piece of crap, were initially made for use in radio stations for advertisements (not much tape (i.e. less weight thus less force/abuse involved), And a moving head with serious alignment problems. But, their PORTABILITY was a revolution!

8 tracks were meant to be thrown away when that ad campaign was over). essentially same width track as cassettes (8 tracks on 1/4" wide tape), and twice the speed of cassettes, 3-3/4 IPs. Never advanced like Cassettes did.

The beloved consumer loved portability and like mp3, accepted reduced quality for quantity, reduced cost.

improvements along the way: better tape formulations, different bias types, more precise mechanisms, 6 heads AND Dolby or DBX noise reduction combined to yield ’better and better’ results from Cassettes

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So, regarding Dolby, as it relates to LPs, is not so easy to decipher.

Let’s not forget, early auto systems weren’t great either.

rvpiano, from your comments I'm not sure you understand how Dolby works.  It boosts selected low level signals during recording and lowers them during playback.  There's no replacing of high frequencies.

Dolby WAS for LPs. The tapes on which the music was recorded, before being cut to LP, were done with Dolby A. The extra two processing steps could not help but to compromise SQ, but for the reduction in hiss. What rvpiano has described has been written of over a long number of years.

Dolby A is very complicated and works on the entire spectrum.

On the older recordings, whether in LP or CD form, you can hear the tape hiss. On the later ones you cannot. Of course, there are other post-production anti-hissing devices that may be in use to mitigate this.

Of course, as has been said, earlier recordings were made with much simpler techniques, to wit, fewer and very carefully placed microphones. That may also account for an airier presentation.

elliottbnewcombjr

... similarly 8 track cartridges, before cassettes, the ultimate piece of crap, were initially made for use in radio stations for advertisements (not much tape (i.e. less weight thus less force/abuse involved), And a moving head with serious alignment problems. But, their PORTABILITY was a revolution! 8 tracks were meant to be thrown away when that ad campaign was over ...

That is not correct. Broadcast carts are similar to 8-track cartridges but have some distinct differences. First, they run at 7.5 ips. (And some ran at 15 ips.) Unlike the 8-track, the broadcast cart has no rubber roller. Instead, the roller pivots up into the cart from the player itself, and then presses the tape against the capstan. Also unlike 8-track, tape heads are fixed in cart machine.

Most cart machines were either mono with a second track reserved for cue tones, or 2-track stereo with a third track for the cue tones. And they weren’t disposable, but were bulk erased and re-used.

The best cart machines were very, very good.

Dolby noise reduction solved several problems that plagued early analog magnetic recording.  Prior to Dolby, it was of critical importance to maximize record levels  in order to avoid excessive amounts of tape hiss and to achieve the greatest dynamic range that the tape was capable of.  Unfortunately, this came at a price.  If you hit the tape too hard, the tape would get saturated and would clip (although gently) the loudest portions of the signal.  Then you had the problem of print through, the propensity of loud portions of the program to impart a ghost image of itself on the next layer of tape (a bit like magnetizing a screw driver by rubbing it on something magnetic).  There was also the issue of additional distortion experienced at higher levels of modulation.  When Dolby was introduced, it was then possible to increase the dynamic range possible by lowering the noise floor (tape hiss) amongst other things.  Tape manufacturers were introducing new, more highly doped oxide coatings that could withstand higher levels of modulation before clipping and backing treatments that would reduce static and print through to a degree.  It was a technological race to reduce noise and expand the dynamic range possible.  This was even more important in small tape formats like the compact cassette where slow speed and narrow track width presented even more of a challenge.  Of course when digital recording became a reality, so many of the problems of analog magnetic recording were at last overcome.  The constant maintenance and alignment needed and the associated cost thereof were certainly not missed.