I am reminded of a lengthy conversation I had with John Eargle. John said that he had discussed this with many of the "old guys." John said that they all agreed that prior to RIAA, EQ was subjective. "Whatever sounded best." As Dennis has suggested it is a challenge and, ultimately, in my experience, somewhat subjective.
When I was teaching my class, I used to have the students listen to, and compare, restorations of the same recording done by different individuals...for example, a Mark O-T versus a Ward Marston version. Sure, one does not know the condition of the discs/pressings each guy used, but the differences in the results could be startling. Then you have someone like Andrew Rose who uses software to analyze the spectrum of a modern recording of a particular work and then apply that to his restoration of an old recording of that work. To my ears, one loses the acoustic of the original recording. For example, his restorations of the stuff recorded at Eastman, sound nothing like the distinctive acoustic of their hall.
Not doubt this is common knowledge in this email list...we apply the notion of EQ to the electrical process. However, when I think about it, I am reminded that a form of "EQ" was a part of the acoustic process. For example, it is known that, especially in the case of pianists, they were expected to adjust the dynamics of their playing, in different parts of the frequency range, to suit the particular qualities of the reproducers of a specific manufacturer.
On Monday, March 4, 2019, 8:49:13 AM CST, Dennis Rooney <[log in to unmask]> wrote:
Recording equalization varied widely from the introduction of electrical
recording until the supremacy of the RIAA curve in the mid-fifties. The
ascertaining and applying the correct playback equalization is one of the
most challenging aspects of disc playback.
Other respondents will supply more information in answer to your queries.
On Mon, Mar 4, 2019 at 9:26 AM Steve Smolian <[log in to unmask]> wrote:
> Companies that made 78s electrically used different systems at different
> times. This was usually indicated by a code in the dead wax, either as
> part of the matrix number or in another area. W in a circle was often used
> for Western Electric, for example. C was used by Columbia to indicate
> their own system about which I know nothing- was this their own development
> or licensed from an outside source?
> Has anyone noticed a change in recording characteristics after the date
> this was changed? Does this affect the playback equalization settings?
> Has there been a study of these systems, dates, etc.?
> If there was no change, there's not much use chasing down some of this
> Steve Smolian
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