Recording the Polyphonic Choir arranged in a circle using the Blumlein technique(Letto 171 volte)

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 offers a 360° stereo panorama, ensuring detailed and immersive sound quality. However, it is less suitable for recording live concerts due to stage limitations, as some of the singers would have their backs to the audience.

There are other recording techniques that may be more appropriate for choirs arranged in a semicircle or in a line, such as XY, ORTF, corolla technique, and spaced technique. These techniques offer versatile solutions for different choral configurations and recording environments.

To learn more about these and other details on choral recording, I invite you to consult my new manual, “Recording Polyphonic Choirs with Ease: A Manual of Professional Techniques Treated Simply for Choir Directors and Aspiring Sound Engineers”, available on Amazon, Apple Books and directly on this site with a discount of 25%.

Here's how to use the Blumlein technique to record your polyphonic choir.

Blumlein Technique 

It offers 360° stereo panoramic recording with perfectly phased coincident microphones.

Recommended placements for the Choir

The Blumlein recording is ideal, with excellent results, for choirs arranged in a perfect circle and is also valid for very large choirs arranged on a single level (even 40 choristers, for example).

It is almost never advisable for choirs in a line or arranged in any way other than a circle, unless in environments with near-perfect acoustics, such as a well-designed concert hall.

The Blumlein technique is one of the best for stereophonic recording, used to obtain a detailed and immersive sound image.

Microphones to use

You need two variable polar pattern microphones set to a figure-of-eight directional pattern, which capture sound from both the front and rear, cancelling out sounds coming from the sides. 

Microphone arrangement

The two microphones are positioned with their capsules overlapping, not touching, forming a 90-degree angle. This configuration allows for 360-degree stereo sound, providing complete coverage of the room. SEE FIGURE

Distance between capsules

The microphone capsules, although not touching, are practically coincident, meaning there is no significant distance between them. This completely eliminates phase problems.

Positioning

This technique involves positioning the choir in a perfect circle with the microphones at the center. The distance of the microphones from the sound source can vary, but it must be sufficient to capture a balanced sound image without being too far away to reduce the impact of ambient reverberation; in fact, it's preferable to keep it as close as possible.

Advantages

The Blumlein technique is appreciated for its ability to capture a very detailed and immersive stereo image of a choir arranged in a circle, with a clear separation between the left and right channels, completely eliminating phase problems.

In summary

The Blumlein technique uses two microphones positioned with their capsules overlapping and at a 90-degree angle to each other, both with a figure-eight characteristic. This configuration allows for detailed and immersive sound recording with great homogeneity.

PRO

TimingThe Blumlein technique offers perfect phasing thanks to the coinciding capsules, eliminating phase problems.

Naturalness: Blumlein offers an extremely pleasant and immersive sound representation, with excellent separation between channels, recreating a three-dimensional listening experience. 

Homogeneity: Remarkably effective in 360° full-circle arrangements, ensuring even and detailed sound distribution for all pitches. 

Controlling ambient reverberation: It significantly reduces the incidence of room reverberation, since the figure-eight microphones pick up less reverberation from the sides and because the singers arranged in a circle act as a barrier to 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 mic stand.

AGAINST

Stage usability for live recordings: Poor, because half the choristers will have to turn their backs to the audience. 

Versatility in post-production: in the mixing phase it allows few differentiated controls on 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 recording of a choir arranged in a circle

Arrange the choir in a perfect circle, pressing the singers shoulder to shoulder just enough to form a wall; this will minimize the distance from the microphones and the penetration of reverberation.

Position the microphone stand, as described above, in the center of the choir. For a four-section choir, ensure that each front and back of the two microphones corresponds approximately to one section. Make sure all singers are the same distance from the microphones.

For soloists

In the case of a soloist, it is preferable to position it at the edge between one microphone and the other, to ensure central positioning in stereo reproduction. 

It is also possible that he will take a step or two forward towards the microphones if necessary to increase the volume of the sound being recorded.

For more information on recording a polyphonic choir, see the manual:

Recording Polyphonic Choirs with Ease: A Handbook of Professional Techniques, Simply Handled for Choir Directors and Aspiring Recording Engineers - Click HERE