[78-L] Binaural, duophonic, etc.

[Steve Williams]

Mike Biel is correct.  I was referring to the Blumlein "Matrixed" method of
using a unidirectional wide pattern cardoid facing forwards, which is summed
with the left-pointing cardoid and subtracted from the right-pointing mic -
Or something like that.. :-) But anyway David is right, that is not a
correct method of capturing accurate "two-ear" imaging but can provide
exceptionally realistic sound for playback on two speakers.  (I was at work
and typing hastily.) When referring to Binaural, Stereo etc. I was going by
current-day understanding of their meaning, I realize the terms were used
differently in the past.

I have the 1952 Mercury Wilbur DeParis Cook "Binaural" LP, and wonder how on
earth anyone expected to get proper results using a twin spiral.  (Many many
years ago I stumbled upon a hoarder-of-anything who happened to have a NIB
Cook arm among his detritus.  I begged and pleaded to get it from him, who
didn't even know what it was, to no avail.)  But regardless, having two
channels is just the start of the equation; most critical is that accurate
timing of the two channels is necessary to maintain accurate phasing to
preserve the imaging used by the ear to judge direction and distance of the
source.  All early forms of record-playback equipment, except multitrack
film, could not preserve that accuracy. Even early CD players which used
only one DA convertor were anathema to Golden ears who could detect the
timing error introduced between the two channels. Staggered-head tape
machines were getting there, but still fussy, until finally stacked audio
heads and single-track record cutting were developed.  I guess the Decca
vertical-Horizontal matrixed method of cutting was similar to the Blumlein
matrixed mic pickups, and FM radio with the AM sideband subcarrier providing
the difference signal to the FM summed channel. 

Steve Williams..

Date: Wed, 20 Apr 2011 14:02:08 -0700 (PDT)
From: DAVID BURNHAM <burnhamd at rogers.com>
Subject: [78-L] Binaural, duophonic, etc.
To: 78-L at 78online.com
Message-ID: <414652.32411.qm at web88103.mail.re2.yahoo.com>
Content-Type: text/plain; charset=us-ascii

Dan Van Landingham wrote:

"Binaural" refers to a method of recording that mimics the human
ear. - "Two Sounds." The microphones are literally mounted on a Styrofoam
head in some cases, or a single crossed-8 cardoid stereo mic is used.  The
listener wears headphones.  

~~~~~~~~~~~~~~~~~~~

As dl has pointed out, Duophonic was a Capitol term for simulated stereo. 
 Binaural recordings have to be made using microphones spaced approximately
the 
same distance apart as the distance between a pair of ears, just like stereo

photography uses two cameras which are eye-spaced apart.  In both cases the 
signal for the left ear/eye cannot reach the right ear/eye or it won't work.

 That's why headphones or some sort of glasses must be employed respectively

BUT the second half of the above statement is not only wrong, but is
confusing. 
 There are several different kinds of mikes, based on polar patterns;  two
of 
these are Cardioid and figure of 8.  Crossed figure of 8, (or bidirectional)

mics will yield superb stereo recordings reproduced on speakers.  This is
known 
as an XY system and was regularly used by BBC and EMI in the early days of 
Stereo.  The system was invented by Alan Blumlein and bears his name.  A 
bidirectional mike is also known as a cosine mike because the level of
pickup is 
proportional to the cosine of the angle of incidence on the mike.  This may 
sound confusing but what it means is that this particular pickup is ideal 
because when your position to the mike is 90 degrees, which in an XY system
is 
the direction from which the right signal will be arriving to the left
channel 
mike, the output is theoretically zero, (the cosine of 90 degrees is "0").
At 
45 degrees, which is the angle at which each mike will be picking up a
centre 
sound source, the output of each mike is reduced by half.  If a speaker
walks 
from the extreme left to the extreme right of an XY pair of figure 8s, his
voice 
level will not vary and the direction of the image will be identical to his 
position on the sound stage.  

Crossed cardioids, on the other hand, produce a less than ideal stereo
image.  A 
cardioid mike is only down a couple of dBs at 90 degrees so a signal from
the 
right side of the sound stage will produce a considerable signal to the left

channel mike.  If the same speaker walks across a XY pair of cardioid mikes,
the 
image will never be at the extreme left or right and the voice will be
louder 
when he is at the centre, (called centre channel build up).  

In any case, neither of these situations will produce binaural recordings 
because the inter-channel time difference which is required for binaural 
reproduction is totally absent when using a coincident stereo mike.

db

------------------------------

Message: 9
Date: Wed, 20 Apr 2011 19:26:35 -0400
From: Michael Biel <mbiel at mbiel.com>
Subject: Re: [78-L] Binaural, duophonic, etc.
To: 78-L Mail List <78-l at klickitat.78online.com>
Message-ID: <4DAF6BAB.7040701 at mbiel.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 4/20/2011 5:02 PM, DAVID BURNHAM wrote:
> Dan Van Landingham wrote:
>
> "Binaural" refers to a method of recording that mimics the human
> ear. - "Two Sounds." The microphones are literally mounted on a Styrofoam
> head in some cases,

Let me mention again that this use of the word was not solidified until 
the 1960s.  Prior to this binaural was used for just about any 
two-channel recording, including some that have w-i-d-e separation.

>   or a single crossed-8 cardoid stereo mic is used.  The
> listener wears headphones.
>

The explanation below is quite good, but I think that the above 
description might have been mis-understood because the wording is a 
little confusing.  Blumlein and others didn't always use a pair of 
bi-directional with one facing forward and the other facing sidewards.  
Sometimes a cardioid is used facing forward and the bi-directional 
pattern is facing sidewards.  I think this is what is meant in this 
description.  Using a cardioid as the forward facing mic instead of a 
bi-directional reduces pickup from the rear, such as audience noise and 
hall reverberation.   Stereo mics like the AKG C-24allowed for the 
changing of the patterns -- in the case of the C-24 even from the 
control room while listening to the results live!

Mike Biel  mbiel at mbiel.com
> ~~~~~~~~~~~~~~~~~~~