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
(\__/)
(='.'=)
(")_(") Smurfen:RIP
