[78-L] Groove spacing - groove width

[Inigo Cubillo]

Thanks all for the interesting & useful links.
I usually play 78s on modern equipment thru standard commercial audio amp +
Esoteric Sound Re-Equaliser. And I've found the Rek-o-kut curves the most
faithful of all, because they go deeper enough to tell the several curves
in use by a given maker at a given time. So for instance I try mid-30s
Victors with either 300 or 500 turnover, and some sound good with 300,
others with 400 or 500. So recording engineers were not fully regular in
their EQ choices for recording. But sometimes I play 78s on the HMV 194,
the second size re-entrant, and there you don't notice as much these
changes, due to the limited Freq range. As much what you can tell is that
some records sound a bit more boomy, or that you hear more treble.
Generally, when treble is stronger, it is in the mid-high range, not too
agreeable, kinda shrill.

Spanish EMI recordings from early forties had a strange EQ. They seem to
have a 500 turnover, but the treble boost is very high, kinda 6kHz or maybe
more... Dunno which kind of microphones or EQ curves they used. This style
seems to be used from 1945 up to 1949, maybe starting earlier. I have to go
thru my database for the 0KA/2KA matrixes. The engineer signatures have
something to do with this. A nice investigation work to be done,
correlating matrix nos and engineer signatures with a careful listening...
They used the square symbol, or the slashed square later, for HMV
recordings, and a circled C for Odeon and Regal brands. Nice work.... Still
pending. Nevertheless, -KA matrixes prior to this era, maybe 1934 to 1940,
sound different. The treble boost was pretty low, and the bass too thin
also. For these, I sometimes use a 700 turnover and a general treble
reduction, for there's a shrillness very disturbing... I still have to do
the investigation for the whole Spanish EMI production in the 1934-1950
period.

Spanish Columbia was a different matter. Starting in 1935, when they cut
all relationship with EMI, EQ was different, for up to '35 they used d
European Columbia standard EQ for the (W)K matrixes. When the independent C
matrix series was started in '35, they seem to use EQ similar to the US
Columbia (400-500 turnover with -10/-12dB @ 10 kHz roll-off). After '43 and
the contract with UK Decca, Spanish recordings seem to follow the Decca
system, and the quality is astonishing. Prior to '43, the quality was also
pretty good, since the old days. When Regal brand was used in Spain, under
the double contract with UK-USA Columbia, '23 to '35, Spanish recordings
were of a very good quality. You notice this specially on the orchestral
and band recordings. Studio sound is dry for orchestral recordings, but the
fidelity is good. Check yourselves the Sinfónica de Madrid recordings from
1930 with Arbós conducting, which were good enough to be published by CBS
in the US, still present in the 1947 Columbia catalogue (Spanish Music I
and II, sets M-146 & 331, and De Falla's Three Cornered Hat, set X-38).
Hear also the Marina opera (set OP-11) also recorded in 1930. Other Spanish
Columbia recordings in the 1947 US catalogue (Nights in the Gardens of
Spain) are of much later facture. These maybe arrived to the US Columbia
catalogue after the 2ww, I don't have data from previous US Columbia
catalogues.

Saludos,
Iñigo