[78-L] Speed vs. Frequency

[DAVID BURNHAM]

Michael Biel wrote:

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.

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I am, of course, aware that cutting styli aren't conical and I know about eliptical styli.

But, unless I am mis-informed, (which is quite possible),  surely the various dimensions, (width, front to back, etc.), are proportional.  A 3 mil groove is cut with a stylus which is much less than 3 mil front to back and a 1 mil groove is cut with a stylus which is much smaller than 1 mil front to back.  But the proportions must be roughly the same.  Similarly eliptical playback styli have the same proportions whether they are 3 mil or 1 mil.  So all of these proportions being the case, I still believe a 3 mil groove would have to be recorded at 100 rpm to match the sound quality of the LP.  If I remember correctly, eliptical styli were a product of the late 60s and ten years earlier, the more complicated characteristic of the stereo groove is what required the playback stylus to be reduced from 1 mil to .7 mil.  As a side thought, this was quite a change when playing mono LPs.  It is like reducing a 78 stylus from 3 mil to 2.1 mil which is
 near the low end of most collectors' various sizes of playback styli, (2, 2.5, 3, 3.5 and 4 mil).  So .7 mil styli must have ridden quite low in the mono LP groove.

All of this being said, dl is correct that it would be a nightmare trying to cue up an LP with 30 or more tracks on it, so for this reason, 78 rpm records are more suitable.

db