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Recording a Polyphonic Choir Arranged in Line with the Spaced Technique 

Coro Tecnica Spaziata - The Alessandro Fois & Friends Blog - alessandrofois.com


Article by: Alessandro Fois

Biografia di Alessandro Fois

Alessandro Fois, born in Cagliari, is a musician, composer, pianist, arranger and sound engineer. Since 2014, he has also been a writer, blogger and webmaster. After living in Oristano and Cagliari, he moved to Ivrea, where he runs Lycnos, an audio, video and web services studio, and the Glamour Recording Studio. He studied piano, music theory and composition at the Cagliari Conservatory, specialising in sound recording with Fonoprint and Sony Italia. He perfected composition and arrangement with Mogol at C.E.T.. He has explored various musical genres, including classical, jazz, blues, pop and progressive, composing for Italian artists and participating in live concerts. He released the album 'Dialogue', while his new project is 'Kaleidoskope'. He is co-author of the Sardinian-language musical 'Boghes de Domo', also directing and performing. He has written soundtracks for RAI, advertising music and for prestigious events such as those of Ferrari. For over 25 years, Fois has managed the

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Recording a Polyphonic Choir Arranged in Line with the Spaced Technique

The Spaziata technique is one of the main recording techniques, also renowned for capturing the sound of a polyphonic choir arranged in a straight line, and the most widely used when recording live concerts because of its better scenic usability compared to other techniques.

There are other recording techniques that may be more appropriate for choirs arranged in a semicircle or in a line, such as XY, ORTF, the corolla technique and the Blumlein 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%.

See also the other Audio and Music manuals at the following link: Books and Manuals

Here's how to use the Spaced Technique to record your polyphonic choir:

Spaced Technique 

Optimised multiple directional shooting of groups of choristers with non-phase spaced technique.

Recommended positions for the Choir

The Spaced shot is ideal for choirs arranged in a line on a single level or up to 3 levels on top of each other, with a front width of 2 metres or more.

It is almost always recommended instead of the ORTF technique, in particular, if the pick-up front (i.e. the chorus line) exceeds 3 metres in highly reverberant locations and 4 metres in locations with moderate reverberation

It can also be used successfully with a choir arranged in an enlarged semicircle (moon-slice).

Microphones for use

It uses cardioid microphones (or variable polar figure microphones set as cardioid), in a number of 1 microphone per group of 3 choristers arranged on the baseline.

Microphone Arrangement

Position the microphones in a line, each in front of a group of 3 choristers, keeping the microphones at a distance of exactly 150 cm between the microphone capsules, to ensure homogeneous recording and optimise phase coherence. The 3 choristers, arranged shoulder to shoulder, should be well centred in front of the microphone.

Advantages

The spaced technique, if optimised correctly, offers good sound coverage for choirs arranged in a line, allowing for a balanced take, a wide stereo image and a fair amount of microphone volume management in post production during mixing (and thus also of choir sections).

PRO

  • HomogeneityIf well executed, ensuring uniform coverage for all choristers.
  • Versatility: Can be used with choirs arranged in a single-level or multi-level line.
  • Environmental Reverberation Control: Significantly reduces the incidence of reverberation if microphones and choristers are correctly positioned.
  • Scenic Usability for Live RecordingsIf small cardioid type condenser condenser microphones supported by poles that are not too bulky are used, the stage impact of the microphones will not be too obtrusive. On the other hand, this technique is the best for filming a choir in line, which is the classic and ideal positioning for the stage requirements of concerts.

AGAINST

  • Fasatura: The technique does not allow for perfect phasing, but optimising the distance between the microphones allows for improved phase coherence, thanks to the 2.5:1 ratio between the reciprocal distance between adjacent microphones (cm.150) and that between the microphone and the choristers (cm.60)
  • NaturalnessIt may not offer the same naturalness as other phased techniques such as Blumlein, ORTF or XY.
  • Ease of useThis is a more complex technique that will require more time and attention to get the choristers' and microphones' positions right, which is essential for an optimal result.

Criteria for the spacing of a chorus arranged in line

In this case, we are in the presence of an unphased shot and therefore have to try to optimise it.

The technique involves an arrangement of several microphones lined up in front of the choir, varying in number according to the number of choristers involved

The phonics rule says that phase optimisation is fully satisfied when the distance between a microphone and an adjacent microphone is at least 3 times the distance of a microphone from the sound source to be picked up, and is sufficiently satisfied when this ratio is at least 2:1. With 3:1 there is in fact an abatement of about 89% of the phase-shifted direct sound, while with 2:1 this abatement is 75%.

With the method that is suggested here, the ratio is almost optimal, at 2.5:1, with the 84% approximately reducing the direct sound out of phase.

With the above in mind, here are instructions for precise positioning of choristers and microphones.

Number of Microphones: Calculate the number of microphones needed by dividing the total number of choristers by 3. Add a microphone if there are 1 or 2 advanced choristers (not divisible by 3). Therefore, consider that you will need 4 microphones for 12 choristers, 6 microphones for 18 choristers and 8 microphones for 24 choristers, without prejudice to the possibility of distributing the choristers themselves over several levels (see below), thus economising on the number of microphones required.

Distance between Microphones: Maintain a distance of 150 cm between adjacent microphones to avoid phase problems.

Positioning the Choristers: Each microphone assigns 3 choristers positioned shoulder to shoulder. Each chorister must have their mouth 60 cm from their microphone, therefore the 2 side choristers of each trio must overlap the middle one by about 15 cm and point their mouths towards the microphone. The microphone must be positioned straight or sloping slightly from above; in the case of recording during the concert, it is permissible (by way of compromise) for the microphone to point from below towards the mouths, so as not to encroach scenically on the soloists' faces. This arrangement, if observed precisely, will ensure maximum homogeneity of the recording for all choristers and also minimum penetration of ambient reverberation into the microphones. (STUDY THE FIGURE BELOW CAREFULLY) 

Coro Tecnica Spaziata - The Alessandro Fois & Friends Blog - alessandrofois.com

Coro Tecnica Spaziata - The Alessandro Fois & Friends Blog - alessandrofois.com

Diagram of a line-up of 18 choristers arranged on a line 9 m long, filmed with 6 microphones (1 for every 3 choristers). Note the distance of 60 cm of each microphone from each chorister (obtained by overlapping the side choristers of each trio of choristers by 15 cm) and the distance of 150 cm between one microphone and the other (ratio of 2.5:1 between the distance between the microphones and the distance of one microphone from the choristers).

Management of Advanced Choristers: If 1 chorister advances to the count of 3 choristers per microphone, position him/her as if he/she were the central chorister of a group of 3, i.e. centrally in front of the microphone at a distance of 60 cm, as for the others. If 2 choristers advance, position them together, shoulder to shoulder, instead of a group of 3, centrally in front of the microphone at a distance of 60 cm.

Choir reprise in line arranged on multiple levels

In the case of a larger number of choristers, you will have to equip yourself with more microphones and a higher number of input channels in the sound card, or you will have to distribute the choristers over several levels, one behind the other, so that you always maintain a base line of 3 choristers per microphone.

In fact, in height, the pick-up angle of a microphone will be able to properly handle up to 3 levels of overlapping choristers (the expedient will offer better results if the rear levels are raised gradually by means of a multi-level modular platform).

You will therefore assign each microphone

  • 3 choristers on 1 level
  • 6 choristers on 2 levels 
  • 9 choristers on 3 levels

Therefore, with 8 microphones, appropriately placed side by side in a line at a distance of 150 cm from each other, you can manage up to a maximum of 72 choristers, assigning to each microphone 3 choristers x 3 levels = 9 choristers. 

Use microphone stands capable of good elevation (check that they are stable) and always point the microphones from the front but raise them a little to direct them towards the midpoint of the 2 or 3 levels.

Finally, make sure that the distance between the mouths of the choristers of the whole group and the microphones does not exceed a maximum of 70-75 cm.

Some notes

It is possible to use fewer microphones, e.g. by assigning 4, 5, 6 or 7 microphones to each chorister on the baseline. This will oblige you to move the microphones away from the choristers in order to pick them all up evenly and, consequently, to distance the microphones from each other to correspond to the 3:1 ratio between the distance between the microphones and the distance of the microphones themselves from the choristers, which is essential for correct phase coherence. It is therefore possible that a gap is created between one group and another. In this way, the penetration of reverberation with respect to the direct sound will increase greatly, even to quadruple in the case of 6 or 7 choristers per microphone on the baseline.


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