[78-L] acoustic recording

[Michael Biel]

David Lennick wrote:
> DAVID BURNHAM wrote:
>>  
>> And the speed stayed in use for production libraries till 1968 because of 
>> superior fidelity and ease of cuing in studios.
>>
>> dl
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Well that was a little mis-guided since, as pointed out here a few weeks ago, the Lp, with its micro-groove, was capable of higher quality sound than the 78 with its 3 mil groove.  A record with a 3 mil groove would have to rotate at 100 rpm to match the sound of a record with a 1 mil groove rotating at 33.3 rpm.
>>
>> db
>> _______________
>>     
>
> You're ignoring the fact that production library discs were not sold to the 
> public but were specifically for radio, TV and film work where a microgroove LP 
> with 36 short music cues would be destroyed in the first few uses, where 
> individual tracks would have to be marked with a grease pencil so the op would 
> play the right track (live on air many times), and where the extra fidelity 
> wouldn't matter because of the limited frequency on air. And those late 
> Chappells and Boosey & Hawkes vinyl 78s outplay anything on LP from the same 
> period.
>
> dl
>   
The groove dimensions vs top frequency is not a factor of the width of 
the groove but the size of the stylus point front-to-back.  That is why 
eliptical styli are theoretically capable of higher frequency response.  
Broadcast styli were usually 2.5 mils conical, not 3 mils.  Since 
cutting styli are chisel shaped, they have a smaller front-to-back 
dimension than playback styli.  They also have burnishing facets to 
polish the groove it just cut, and this might also affect the top 
available frequency it could record.So it is not a three-to-one factor, 
more like a two and a half-to-one in the conical styli days.

I do take exception to David's contention that broadcasting has limited 
frequency response.  FM mono extends to 20 K and FM stereo extends to 15 
K.    I don't know about Canadian law, but I do know that in the U.S. 
there was no upper limit on frequency response on AM until the late 
1990s.  Before then it was routine for AM stations to have response 
beyond 10K, usually uip to 13 or 14 K.  The limitations in AM sound is 
due to the lousy radios made since the mid-70s.  Radios from the 50s and 
60s are much better before manufacturers purposefully reduced their 
bandwidth because of increasing interference from new short-spaced 
stations.  Top response now is allowed to 10 K and must be filtered 
beyond that.  There are only a couple of radios made today that can meet 
that response, such as the GE SuperRadio 3 and the Grundig S-350, but 
the stations are broadcasting to 10K, at least here in the U.S.  

Of course in those days, network lines were a limiting factor, not the 
transmitters.  The main trunks in the U.Sl went to 10K by 1935 and some 
of the loops went to 15K in the 40s.  They did  cut back in the 50s and 
60s, but the use of satellites for network deliver bring it all back to 
15K now.  Local stations and local programming were not limited by the 
lines, and local studio-transmitter lines are routinely 15K in the U.S.  
Great Britain did have a 4.5 K limitation, though, and this might have 
also been the case in mainland Europe..

Mike Biel  mbiel at mbiel.com