Contrabass Digest

2000-08-26

Date: Sat, 26 Aug 2000 08:43:49 +0100
From: David Bobroff
Subject: [CB] 1812

Grant said:

>As for extreme low percussive bass, the recording that springs to
>mind is the Telarc version of the "1812".  I forget if it was "direct
>to disc", or just one of the first to adopt digital recording.  I
>remember when it first came out on vinyl, and they made a big deal of
>the size of the track excursion for the cannon blasts.

It was not direct-to-disk but rather one of the early all-digital
recordings.  The piece was recorded in Music Hall in Cincinnati and the
canon were added later.  A roommate of mine in college had this on vinyl in
the pre-CD days.  You could actually see the canon blasts on the disk's
surface.  It took him some time to get his stylus to track it without being
kicked out of the groove (he had really good equipment, too).

Cheers,

David Bobroff
---------------------------------------------------------

Date: Sat, 26 Aug 2000 12:01:52 +0000
From: Lawrence de Martin
Subject: Re: [CB] Bass hearing

Forgive me if I go on a bit, but reality in this case differs from "common
knowledge".  Hearing is much better than most scientists and engineers imagine,
especially in the contrabass and below.

Ron Follas  wrote:

> The issue becomes problematic when there are too few
> vibrations to create a pitch, for example, a staccato note in the lowest
> contra range.  Creating only one Hz does not give the ear enough information
> to create a physical comparison for pitch.

I  have not yet found exact figures from the psycho-acoustical studies, but Harry
Olson states in "Modern Sound Reproduction" that human hearing can determine the
pitch of a note in fewer cycles than electronic measuring equipment, which was
analog at that time.

What I am referring to is the frequency of the rhythm, which is low enough in
pitch that it is quite accurately determined in one cycle.  If the rhythm is
expressed as a series of sharp impacts like a snare rim shot, the energy content
of the rhythm frequency is quite low, but we hear it clearly as time.  Studies
have shown that trained conductors have a sense of rhythm that is accurate to
within a second over a thirty minute symphony, which is just like absolute pitch.

If the rhythm is expressed as notes on an instrument that starts and stops
gradually like a bowed bass, legato wind or organ pipe, the energy of the rhythm
frequency is somewhat greater but the accuracy of the rhythm is harder to hear.
Yet, a proficient musician plays in phase to the rhythm, just as a bass section
plays in phase with each other* - that is, the accuracy of the rhythm is a
fraction of a cycle of the note, which is a tiny faction of the rhythm frequency.

If a bass instrument which can start and stop in an instant, like a plucked
contrabass or piano, plays a series of staccato notes the energy of the rhythm
frequency is quite large as expressed by the pure tone component (sine wave).  I
myself am a clumsy amateur bass guitarist, but I can produce notes that are as
short as five integral cycles, and they sound much better than notes that have a
fractional number of cycles.

When the rhythm frequency is filtered in a recording chain, most severely by
speakers, audible time distortion results.  It has been shown that speakers which
have frequency response extended to 10Hz sound better at normal listening levels,
even though a continuous tone of 10Hz needs to be over 100dB to be audible.

Futher, most speakers achieve bass volume through resonance, which also distorts
the beginning and end of notes near the resonant frequency.  the staccato notes
are shifted later in time; and the beginning and end of the notes go off-key.
This effect is clearly audible, even though it affects only two or three cycles
of the note. Speakers which are designed for amplification of electrical bass
instruments typically have reduced mechanical resonance which causes weak bass.
The design of electric bass guitars places the pickups where the fundamentals of
open strings are attenuated over 10dB to avoid the speaker time distortion.

Because this is a universal characteric of cone speakers, recording engineers and
producers reduce the bass transient content of recordings.  How many times have
we seen the bass rolloff switch engaged on the microphone?  The microphone moved
away from the bass instrument?  Bass equalization, gating or compression?

Professional condensor microphones have a bass rolloff above 20Hz - I have
researched Neumann, AKG, Sennheiser, Beyer, Sony, Audio Technica, Schoepps,
Telefunken, Shure and Rode.  This is sufficient for brass, string and wind note
frequency, but inadequate for rhythm frequencies.  I just obtained an Equitek
E200 which has response to 10Hz through a novel circuit involving rechargeable
batteries to research bass hearing and better quantify it.

I again extend the offer to participate in my experiments by recording your
contrabass work.  I can reasonably travel between New York and Boston to obtain
good acoustics.

Larry de Martin

*because the bass section is physically contained within a wavelength of the
lower octave fundamentals  (4 meters or so), they can play in phase and the
volume increases 6dB with the doubling of players from one to two or two to
four.  Because a violin section is spread over many (shorter) wavelengths, they
have random phase and the volume only increases 3dB with every doubling of the
number of players.  This is why violin sections get so large.

***End of Contrabass Digest***

 
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