Re: [ARSCLIST] Equalizers

["Copeland, Peter" <Peter.Copeland@xxxxx>]

Dear All,
    Sorry to be so late in joining this discussion. As the former Technical
Manager of the British Library Sound Archive, I have done quite a lot of
work researching these matters, which include a number of different
"standard" equalisation curves (US Columbia's "LP" curve, RCA Victor's for
their rival 45s, the NAB curve, and others). The main problem from where I
sit is to determine *which* curve(s) were in use at *which* times. Since I
retired, I have been involved in listening tests, generally comparing a
modern ("RIAA") reissue with the same performance recorded in its original
format. As a general rule, I am attempting to define equalisation changes by
using using matrix-numbers, which were often (but not always) allocated by
the mastering engineer himself.
    Clearly this work will *never* be completed; but if anyone wishes to see
the latest version of the disc equalisation section of my Manual, and/or a
couple of papers I have published on the subject, please write to me offline
at peter.copeland@xxxxxxxxxxx
    Incidentally, I disagree with George Brock-Nannestad's assertion that
cutterhead damping played a part. All such "standard" curves have a 3dB
point right in the middle of the frequency range - always between 250Hz and
3.18kHz - and this is perfectly clear, even on a small loudspeaker. Indeed,
I personally was "hit" by a change in the European Standards for 19cm/sec
magnetic tape, which also applied to 16mm magnetic film soundtracks. Various
film directors suddenly grumbled that my films sounded "woolly" on
transmission.
    And another can-of-worms concerns what happened when LPs and 45s were
taken from "metal parts" (usually originals which had been cut at 78). These
nearly always reproduce the original frequency spectrum precisely - despite
what the official *microgroove* equalisation may have been!
Peter Copeland

-----Original Message-----
From: Don Cox [mailto:doncox@xxxxxxxxxxxxxx]
Sent: 18 July 2004 16:04
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Equalizers

On 18/07/04, Steven C. Barr wrote:

> Keep in mind that prior to some point in the 1930's, equalization was
> "made up on the spot" by the recording engineer, and there was no
> standardization of any type, even within labels. The later controls
> on amplifiers and pre-amps refer to a fairly-standardized intra-label
> curve (one per label). These controls appear on most "hi-fi" gear of
> the fifties and early sixties, but apply only to records of their
> era...equalization of earlier 78's has to be done "by ear" (unless
> someone can decode the cryptic notes found in surviving recording
> ledgers if any exist)...

Also the manufacturing tolerances on resistors and capacitors in those
days were very wide, so even if somebody designed a circuit to give some
desired EQ, the results could be somewhat diferent.

Regards
--
Don Cox
doncox@xxxxxxxxxxxxxx


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