The speeds of these old records actually varied somewhat. At some point they were standardized at 78, so having variable speed capability on your turntable for the earlier records is desirable.
There also wasn't a standard equalization curve at that time, or for early LP's, for that matter. There are phono preamps available (from Graham Slee, for example) to compensate for this.
There also wasn't a standard equalization curve at that time, or for early LP's, for that matter. There are phono preamps available (from Graham Slee, for example) to compensate for this.