Recording the Polyphonic Choir arranged in a circle with the Blumlein technique
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Pianist, Composer, Arranger, Sound Engineer, Writer, Blogger
Alessandro Fois is a musician, composer, pianist, arranger and sound engineer. Since 2018, he has also been a writer, blogger and webmaster. He currently resides in Ivrea (Turin) where, in addition to the above activities, he manages Lycnos, studio for audio, video and web services, and the recording studio Glamour Recording Studio.
Recording the Polyphonic Choir arranged in a circle with the Blumlein technique
The Blumlein technique is one of the main stereophonic recording techniques, renowned for its effectiveness and simplicity in capturing the sound of a polyphonic choir arranged in a circle. This technique provides a 360° stereo panorama recording, guaranteeing detailed and immersive sound quality. However, it is less suitable for recording live concerts due to stage limitations, as part of the choristers would be standing with their backs to the audience.
There are other recording techniques that may be more appropriate for choirs arranged in a semi-circle or in a line, such as XY, ORTF, the corolla technique and the spaced technique. These techniques offer versatile solutions for different choral configurations and recording environments.
For more on these and other details on choral recording, I invite you to consult my new handbook, "Recording Polyphonic Choirs with Ease: A Handbook of Professional Techniques Covered in a Simple Way for Choirmasters and Aspiring Conductors".available on Amazon, Apple Books and directly on this site with a discount of 25%.
Here is how to use the Blumlein technique to record your polyphonic choir.
Blumlein Technique
It offers a 360° stereo panoramic shot with perfectly in-phase coincident microphones.
Recommended positions for the Choir
The Blumlein reprise is ideal, with excellent results, for choirs arranged in a perfect circle and is also valid for very large choirs arranged on one level (even 40 choristers, for example).
It is almost never advisable for choirs in a line-up or arranged in any other way than in a circle, unless they are in rooms with almost perfect acoustics, such as a well-designed concert theatre.
The Blumlein technique is one of the best for stereophonic recording, used to achieve a detailed and immersive sound image.
Microphones to be used
Two variable polar figure-of-eight directional microphones are needed, capturing sound from both the front and back, cancelling out sounds coming from the sides.
Arrangement of microphones
The two microphones are positioned with the capsules overlapping without touching, forming a 90-degree angle. This configuration allows a 360-degree stereo sound to be picked up, offering a complete shot of the environment. SEE FIGURE
Distance between capsules
Although the microphone capsules do not touch, they are practically coincident, which means that there is no significant distance between them. This completely eliminates phase problems.
Positioning
The use of this technique involves positioning the choir in a perfect circle with the microphones in the centre. The distance of the microphones from the sound source can vary, but must be sufficient to capture a balanced sound image without too much distance to decrease the incidence of ambient reverberation; in fact, it is preferable that it be as short as possible.
Advantages
The Blumlein technique is appreciated because it succeeds in capturing a highly detailed and immersive stereo image of a choir arranged in a circle, with clear separation between the left and right channels, completely eliminating phase problems.
In summary
The Blumlein technique uses two microphones positioned with the capsules overlapping and a 90-degree angle between them, both with figure-of-eight characteristics. This configuration allows sound to be recorded in a detailed and immersive manner with great homogeneity.
PRO
Fasatura: The Blumlein technique offers perfect phasing thanks to coincident capsules, eliminating phase problems.
NaturalnessBlumlein offers an extremely pleasant and immersive sound representation with excellent channel separation, recreating a three-dimensional listening experience.
Homogeneity: Remarkably effective in 360° full circle arrangements, ensuring even and detailed sound distribution for all choristers.
Environmental reverberation controlIt significantly reduces the incidence of ambient reverberation, because figure-of-eight microphones pick up less reverberation from the sides and because the choristers arranged in a circle block out some of the reverberation induced by reflections on the walls.
Ease of useThe technique is relatively simple to implement, requiring only two microphones and a microphone stand.
AGAINST
Stage usability for live recordingsPoor, because half of the choristers will have to turn their backs on the audience.
Versatility in post production: at the mixing stage it allows little differentiated control over the volumes and tones of the choir sections, specifically only a slight adjustment of the volume and tones of two opposing sections at a time
Criteria for the Blumlein recovery of a choir arranged in a circle
Arrange the choir in a perfect circle, squeezing the choristers 'shoulder to shoulder' just enough to 'make a wall'; this will minimise the distance to the microphones and the penetration of reverberation.
Position the microphone stand, as described above, in the centre of the choir; in the case of a 4-section choir, make each of the front and back sides of each of the 2 microphones roughly correspond to a section. Ensure that all choristers have the same distance from the microphones.
For soloists
In the case of a soloist, it is preferable to stand at the edge between one microphone and the other to ensure central positioning in stereo playback.
It may also take one or two steps towards the microphones if necessary to increase the volume of sound when recording.
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