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Tom Fine:

> I don't think very many LPs contained 
> "super-sonic" frequencies, because 
> everyone rolled off at some point to 
> avoid blowing out the cutterhead. 

There are very many LP´s that do contain a very wide frequency response 
and very high cutting levels at high frequencies.

BTW, you do not "Roll Off" the high frequencies by using a low pass 
filter instead you use a high frequency limiter that is user adjustable 
and you can bypass it too.

The high frequency limiter limits the level to a "safe value" to 
provide disks that can be tracked by normal run of the mill cheap 
cartridges.

If you low pass filter the program it will sound very dull ALWAYS.

If you HF limit then the decrease in high frequency level will be just 
very momentary almost inaudible to most persons and the full frequency 
range is always flat to 20 kHz.

So HF limiting is far preferable to low pass filtering.

Disks can be cut containing the full frequency and levels found on the 
master tape with very little problems but most cartridges will turn it 
all into distortion.e due to too high level for any cartridge to track 
securely.

> You are very correct, though, that it's 
>  easier to cut 10kHz than 20kHz at a 
> high level, but what music has high 
> levels of 20kHz in the first place? 

A lot of music, do in fact, have very high levels beyond 10 kHz on a 
peak transient basis.

Muted brass is a killer for sure to record cleanly and if that was done 
cutting can be very good but almost impossible to play back cleanly 
unless the cartridge is the Shure V15 V.

Most pop, rock, synth, reggae etc even classical will on many tracks 
have almost the same level up to 16 kHz, even 20 kHz when you set a 
third octave analyzer on peak hold for the duration of a disk.

That is straight from the master.

How much of that found its way onto the release disk or whatever medium 
seen fit for release is up to the mastering person and his beliefs.

No matter what you do there´s a 50 % chance you will get an angry call 
from somebody telling you that you did wrong. :-)

BTW, the Pierino Gamba/LSO Rossini Overtures DECCA CD 417 692-2 as 
recorded by Kenneth Wilkinson in 1961 has full level up to 14 kHz, 
meaning more or equal level there, 8 to 14 kHz, than what can be found 
in any other frequency band.

This shows enormous care from DECCA´s chief engineer Kenneth Wilkinson 
when setting his recording levels going onto tape to avoid analogue 
tape self erasure.

And my DECCA LP that I bought in 1963 has almost everything there 
despite the very wide frequency range and the very hot outbursts from 
the percussion department to spice the top.

Proving that the cutting department at DECCA was very good indeed at 
that time.

It can be done but only the very best cartridges can track such a disk 
without it going into distorted mess.

> I just don't see any big advantage to 
> half-speed cutting, 

The advantage comes from the very well known fact that most cutting 
heads have a series of high frequency resonances from 5 kHz and up.

One of the worst ones are the Westrex which really makes the top goes 
Hollywood sizzly.

You either love it or hates it.

Neumann cutter heads ZS90/45, SX45, SX15 all had quite audible 
resonances in the audible range and those prohibited the use of much 
feedback to lower distortion since the phase rotation caused by the 
cutter head resonances made that impossible.

The DECCA/London back room boys always tried to get as much quality out 
of the gear they used so disliking the sizzle in the top caused by the 
cutter resonances in their Neumann cutter they hit on half speed 
cutting to make disks that had NO audible resonances in the audible 
range.

If the cutter has a peak at 12 kHz in real time then by using half 
speed cutting this resonance will now be at 24 kHz when the disk is 
played back in real time.

But half speed cutting has more to gain by having the highest frequency 
at 8 to 10 kHz means that the cutter could cut much higher transient 
high frequency information without blowing up.

Your 60W cutter amplifier became a monster 240W by half speed cutting.

Also the channel separation is much improved in the high frequency 
range too.

All that stopped at DECCA/London around 1968 when Neumann released the 
SX68 cutter head which was the very first such device that did not have 
any resonances below 20 kHz.


 -- 
Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: [log in to unmask]

Learn from the mistakes of others, you can never live long enough to
make them all yourself.    -   John Luther

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