Handbook for Sound Engineers

916 Chapter 25

subject of raging controversy and opinion for decades.
Should it be 2, 3, 3½, 4, or 4½ dB down at center?
As is often the case, those closely involved with the
theorizing somewhat lost touch with how a pan pot is
ordinarily used. A pan control usually remains rusted at
an initially set position for hours, days, weeks,
months—however long the mix takes. If a pan pot is
used dynamically for effect during a mix, its very drama
drowns any question of whether it was “a wee bit quiet
in the middle.”

A single pot used as in Fig. 25-91C allows a choice
of central down points by adjusting the relative values
of the source resistors and pot value, but at the cost of
slightly iffy tracking (most pan effect tends to happen at
the extremes of the control travel) and ultimate panning.
When panned hard one way it is nearly impos-
sible—due to wiper-track resistance—for the dimin-
ished side to achieve complete attenuation. If 40-odd dB
is good enough then this may be the one. Shown are
values for a 3 dB down panpot.

During the 70s the BBC had the understandable

problems of multitudinous operators, countless consoles

of varying antiquity, and a considerable number of

console suppliers. Their aim was consistency and to this

end evolved a dazzlingly simple arrangement shown in

Fig. 25-91D recommended for inclusion in new

supplied equipment; it works.

25.13.9 Surround Panning

Surround has many variants, but for the purposes of

discussion here 5.1 will be considered; other formats

have basically similar requirements that may be taken as

a subset or extrapolated from 5.1.

Well, quad is back (and it hasn’t forgiven). At least

in terms of four of the 5.1 signal paths, left front, right

front, left rear and right rear. Panning for these is

achieved in much the same manner as it was in those

chillingly far-off days, a joysick that controls relative

proportions of the source signal to the four output, or a

Figure 25-90. Differential balanced mixing.

Differential bus

drive amplifier

Input

Etc.

Bus

Balanced/differential

Output

Superbal

mix amp

Mix bus

Etc.