Barbershop quartet

What it is

Four unaccompanied voices (tenor, lead, baritone, bass) in close, consonant four-part harmony, with "ringing" chords whose overtones reinforce each other. Men's and women's groups use the same part names. The tenor sits in countertenor range and sings its top notes mainly in falsetto; the lead matches a classical tenor; the baritone a high lyric baritone range with tenor tessitura (Wikipedia, Barbershop music).⁸

Where the sound comes from

• voices: Many incoherent voices whose intensities add; a few loud voices dominate fortissimo.⁶

• Each voice is close to omnidirectional below about 1 kHz.⁷
• Above about 1 kHz each voice is more directional, towards the front.⁷

The sound

No source with levels. Because the chords depend on overtones lining up, avoid close mics and heavy processing (my inference).

Layout

The quartet stands in a semicircle (forum, a barbershop recordist). In Barbershop Harmony Society contests singers perform at a single fixed position in front of the stage mics; the Society dropped a second set of mics placed a few feet outside the quartet because they were hardly used. Singers tune and balance to each other by ear, so the sources say to record them together and not to overdub.^1,9

How loud

Sound pressure level measurements as published. Different kinds of figure (a playing level, a peak, a dose at the player's ear) can't be compared with each other, and neither can figures at different distances.

Recording it

• A pair of small-diaphragm condensers in X-Y, about chest high and 2 ft (60 cm) away; the poster used Earthworks SR69s and says competitions allow only this.
• A moderator: treat the quartet "like a stereo source", X-Y with the angle matched to the spread of the singers.
• Another: four large-diaphragm mics in a semicircle, plus omnis for the room if it sounds good.
• Room matters more than mics: in a small room put singers in the middle away from walls and mics close; in a large room put mics farther away.
• Handheld mics only suit singers who really know mic technique, according to a moderator.
• From a search summary of a Reddit thread (page not opened): BHS sound crews used Schoeps CMXY pairs 42 in above the deck on a boom, and pencil condensers (Schoeps MK 4, Neumann KM 184, Shure SM81, AKG C 480/C 451) are preferred.^1,3

Mics i

1. Neumann KM 184 3 sourcesClose, main pair or array, named, no placement given
2. Earthworks SR69 2 sourcesMain pair or array, close
3. Schoeps MK 4 2 sourcesMain pair or array, named, no placement given

On stage

• Small-diaphragm cardioid or supercardioid condensers on stands or hanging, about 45 cm in front of the first row and 45 cm above the back row's heads; or '2x2': 2 ft in front, 2 ft above the tallest singer, for up to 20 singers.
• About one mic per 6 m of singers; 30-45 voices need two or three.
• Keep neighbouring mics at least three times as far apart as each is from its singers (3:1); with few mics it can't always be met.
• Aim a supercardioid at the back row: the front row is then about 60 degrees off axis and the back row 1.4 times further away.
• Gain before feedback drops fast as mics cover more singers: in DPA's example for 12 singers, six mics lose 17 dB and three mics 25.5 dB against one mic per singer.^10,11,12,13

Problems to watch

• Feedback with monitors behind the choir.
• Hearing loops pick up dynamic mics and cables: use condensers and route cables away.
• Comb filtering from too many open mics.^12,14