I am attempting to set up a couple of micro-
phones to record an Orchestra performance. In
order to achieve a stereo effect, it was my im-
pression that the microphones should be spaced
several feet apart, one on each side of the cen-
ter of the stage.
This is called A-B stereo.
It gives you some intensity imaging but no phase
imaging because the phase differences between the
channels are too great for the brain to make sense
of them. It was very popular back in the 1950s
and 1960s when good directional microphones did
not exist and omnis were the order of the day.
True A-B technique (with smaller spacing) is purely
phase-based stereo, which is the only right kind of
stereo because it imitates human hearing.
Since posting my earlier request, I settled on an approximation of this >"ORTF" method. I am using a pair of Shure SM81 Cardioid microphones. I >probably do not have the angles and separation exactly right, but have
been satisfied with the results.
One thing I found was that the SM81 microphones are extremely sensitive
to mechanical disturbance. Mounted on an extended tall stand, motion
induced by either flexing of the wooden floor or a breeze from the air >handler, resulted in a loud rumble. Apparently the microphones or
connectors were rubbing against each other! Fortunately there is a
Shure vibration isolator that fits the SM81.
The loud rumble was improved using a 55 Hz High Pass filter, but at the >expense of Tympani and Bass Drum levels.
True A-B technique (with smaller spacing) is
purely phase-based stereo, which is the only
right kind of stereo because it imitates human
hearing.
Since posting my earlier request, I settled on an
approximation of this "ORTF" method. I am using a
pair of Shure SM81 Cardioid microphones. I proba-
bly do not have the angles and separation exactly
right, but have been satisfied with the results.
Fred McKenzie <fmmck@aol.com> wrote:
Since posting my earlier request, I settled on an approximation of this >"ORTF" method. I am using a pair of Shure SM81 Cardioid microphones. I >probably do not have the angles and separation exactly right, but have
been satisfied with the results.
So try altering them to get a sense of what it does to the sound.
One thing I found was that the SM81 microphones are extremely sensitive
to mechanical disturbance. Mounted on an extended tall stand, motion >induced by either flexing of the wooden floor or a breeze from the air >handler, resulted in a loud rumble. Apparently the microphones or >connectors were rubbing against each other! Fortunately there is a
Shure vibration isolator that fits the SM81.
The vibration mount is a very good thing, also if possible it is wise to
use a very flexible cable going into the microphone to reduce vibration transmitted through the cable. Olson will sell you a very good windscreen for wind issues.
If you think the SM81 is sensitive to this kind of thing, you should see
what the DPA omnis are like.
The loud rumble was improved using a 55 Hz High Pass filter, but at the >expense of Tympani and Bass Drum levels.
Find out where it's coming from and fix it. If it's an air handler issue, it's possible moving a few feet will deal with it.
--scott
I am trying to record what a person would hear if
they were at the same spot as the microphones, re-
alizing that there are differences.
At a recent concert, I had the two microphones
about 10 inches apart, but pointing in almost the
same direction.
They were about 7 feet above the stage floor, and
about 5 feet left of center. I am very happy with
the results as far as frequency response is con-
cerned.
I am not happy with some instruments not being
heard as loudly as expected ->
and the lack of stereo effect
At a recent concert, I had the two microphones
about 10 inches apart, but pointing in almost the
same direction.
Were they the cardioid SM81s?
Since posting my earlier request, I settled on an
approximation of this "ORTF" method. I am using a
pair of Shure SM81 Cardioid microphones. I proba-
bly do not have the angles and separation exactly
right, but have been satisfied with the results.
Glad to know that. It will be intensity-based
stereo. May I listen to a fragment of your record-
ing, unprocessed and preferably losseless?
Needless to say, I am not a pro!
My recordings are intended to be used by the Con-
ductor and a few key Musicians to analyze the per-
formance.
The H4N recorder is configured to automatically
set the recording level. As the concert progress-
es, the level gradually gets lower. I use "Audac-
ity" to separate each piece, and then use it to
amplify each to approximately the same level,
sometimes more than 10 DB.
Before separating pieces, the .WAV recordings run
about 2 GB per hour. So unprocessed and/or loss-
less fragments would be too big for my limited in-
ternet access!
...and usually have a more wholesome taste and
criterii.
Fred McKenzie:
Needless to say, I am not a pro!
Neither am I.
My recordings are intended to be used by the Con-
ductor and a few key Musicians to analyze the per-
formance.
I should say that the conductor and performers are
more critical audience than the layman listener and
usually have a more wholesome taste and criterii.
If they are satisfied with your work it must be
good.
The H4N recorder is configured to automatically
set the recording level. As the concert progress-
es, the level gradually gets lower. I use "Audac-
ity" to separate each piece, and then use it to
amplify each to approximately the same level,
sometimes more than 10 DB.
So the level is set automatically at the beginning
only? I simply ask the musician to play the loudest
part and adjust my controls for that. Does the H4N
use analog or digital attenuation? The latter is a
bad idea.
I too have used Audacity for simple editing. If you
have to amplify by 10 db then you are using about
30% of the recorder's dynamic range, but if the con-
cert is one indivisible programme it is all right.
Otherwise, I should adjust the levels for every com-
position.
Before separating pieces, the .WAV recordings run
about 2 GB per hour. So unprocessed and/or loss-
less fragments would be too big for my limited in-
ternet access!
That must be a high-definition format. Three min-
utes of CD audio take about 30 Mb in WAV and about
half that space in the lossless format FLAC.
Here's a recording that made using the A-B tech-
nique:
https://soundcloud.com/anton-shepelev/honey-dont-cover
It lasts 2:14 and weights only 12 Mb in FLAC.
I am trying to record what a person would hear if
they were at the same spot as the microphones, re-
alizing that there are differences.
I am not happy with some instruments not being
heard as loudly as expected and the lack of stereo effect.
A concert starts with a tuning note followed by
the Presentation of Colors and National Anthem.
H4N recording level is set by the loudest sound,
often the Bass Drum. By the time the first con-
cert piece is started, level has been set. Over
the course of a 90 minute concert, occasional loud
sounds will reduce level further.
I believe the recording level is digitally con-
trolled.
Whether it is gain or attenuation may be a matter
of point of view!
I was not familiar with .FLAC format. I see that
Audacity can export it. If I do not forget, I'll
check to see if the H4N can use it. There is a 2
GB limit to the size of a file the SD card format
can accept, so a 90 minute concert is broken into
two files. Perhaps .FLAC would help.
Here's a recording that made using the A-B
technique:
https://soundcloud.com/anton-shepelev/honey-dont-cover
Listening on my laptop, your recording is very
clean.
It sounds like you have a nice studio with abso-
lutely no background noise.
In addition to extraneous audience noises, ->
my recordings range from the solo Flute in aquiet passage to the blaring Brass in a loud pas-
sage. I have been tempted to try compression, but
have resisted the temptation.
I am attempting to set up a couple of microphones to record an Orchestra performance. In order to achieve a stereo effect, it was my impression
that the microphones should be spaced several feet apart, one on each
side of the center of the stage.
I came across an article that placed the two microphones together with
front apertures almost touching in a "cross-eyed" configuration. The
right microphone was pointed to the left and vice versa.
I can see where it might be bad if microphones were too far apart. Our
ears are fairly close together and hear things in stereo. Does it make sense to locate the microphones closer together than our ears are spaced?
Fred
On Tuesday, August 19, 2014 at 1:04:34 PM UTC-4, Fred McKenzie wrote:
I am attempting to set up a couple of microphones to record an Orchestra performance. In order to achieve a stereo effect, it was my impression that the microphones should be spaced several feet apart, one on each
side of the center of the stage.
I came across an article that placed the two microphones together with front apertures almost touching in a "cross-eyed" configuration. The
right microphone was pointed to the left and vice versa.
I can see where it might be bad if microphones were too far apart. Our ears are fairly close together and hear things in stereo. Does it make sense to locate the microphones closer together than our ears are spaced?
Fred
My first esoteric encounter with this craft came one evening when my son was doing some guitar rendition with friends. I had a portable Nakamichi tape deck with headphones to hear what was being recorded, and a stereo mic pair that I was obliged to hold in both hands. I did hold then less than a foot apart, and the stereo action was clear. Having a necessary scratch, I temporarily put the two mics together in one hand (to scratch with the other). The stereo held until the mics were less than an inch apart. I then tested that phenomenon and concluded that stereo is achieved when the mics are 2" or more apart. Hypothetically, when they are about 5" apart, they should perform as do our ears naturally. That settles the basic issue.
So why wide mic separations? IMHO, it is to sample two separate orchestra sound fields. On another occasion I witnessed that the 2 kHz etc sound radiation from the violin section (viewed as left of orchestra center) radiates upward to the right (as seen from the audience)so that the left mic will intercept that more than the right mic (as seen from the audience). The right side of the orchestra contains largely horns and brass so it is feasible to procure rich strings via the left mic and strong brass from the right mic. To that extent, the wider separation will provide that separation service. How you craft your mic setup is up to you.
My first esoteric encounter with this craft came one evening when my son wa= >s doing some guitar rendition with friends. I had a portable Nakamichi tape=
deck with headphones to hear what was being recorded, and a stereo mic pa=
ir that I was obliged to hold in both hands. I did hold then less than a fo= >ot apart, and the stereo action was clear. Having a necessary scratch, I te= >mporarily put the two mics together in one hand (to scratch with the other)= >. The stereo held until the mics were less than an inch apart. I then teste= >d that phenomenon and concluded that stereo is achieved when the mics are 2= >" or more apart. Hypothetically, when they are about 5" apart, they should = >perform as do our ears naturally. That settles the basic issue.=20
So why wide mic separations? IMHO, it is to sample two separate orchestra s= >ound fields. On another occasion I witnessed that the 2 kHz etc sound radia= >tion from the violin section (viewed as left of orchestra center) radiates = >upward to the right (as seen from the audience)so that the left mic will in= >tercept that more than the right mic (as seen from the audience). The right=
side of the orchestra contains largely horns and brass so it is feasible t=
o procure rich strings via the left mic and strong brass from the right mic= >. To that extent, the wider separation will provide that separation service= >. How you craft your mic setup is up to you.
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