b.
both the direct sound
and
a
reflected
sound
from
the floorr
waIl
or music stand) and in
plalback
(wtrere
a loudspeakerrs
direct
sound conbines
in
ttre
air with reflections
off room
boundaries and
furnishings). Ihis
pattern
of alternating reinforcenent
and
cancellation causes
an audible
coloration of the sound.
t\rc
things are noterrorttry. One is
ttrat the reinforcenents
and
cancellations
occur
at hanrpnically-related
frequencies.
ftre
other
is that ttre
trnttern
of
peaks
and
dips can
be
variedT i.e.7
tuned,
just
by
varying
ttre
delay tfure. In
alrost
all nornal vocal
and musical sounds, most of ttre energy is found at fundanental
frequencies and
ttreir harmonic
overtones. By
varying
ttre
delay
tire
of a
delay-and-mix
circuit,
we
can easily but
dramatically
alter the
overtone
structure
and ttre
tonal
quality
of any
steady
sound.
Ihe
precise
delay tfunes and
unusually
flat frequency
res[pnse of ttre ffFECIRON II
make it ideal
for
corb
filtering
on
demand.
FIA}GIIiG
If the unit
is
setup
to
produce
conb
filtering and
ttren the
delay
tfure
is snoothly varied, the
Snttern
of
peaks
and
nu11s
will
shift
in frequency. lbdulate the delay tiue rapidly and
the
trnttern
of
trnaks
and nu11s
wi}l
sweep rapidly
up
and
dovm the
frequency
spectrum
trnssing
in
and out of
slznchronization
with
the
frequencies of
musical
signals
and
ttreir overtones.
Select
relatively short delays so ttrat the strncing of
ttre nul1s
corresgnnds to
ttrat of musical. harrnonics.
A.s ttre
delay
is
swept,
at one rorent, ttre odd-nwlcered harronics are
enhanced by
6
dB
-
a
rnorent later, tte harmonic
structure of ttrat note is
sliding
into alignrent
with
ttre
harnpnic
overtones of a different
note.
Ihis
sweeping, shifting
change
is
calIed
"flanging'.
Iro
achieve
iL,
one
need
only setup
ttre
delay
and mixing
as
reE:ired
for
corb filtering and then
activate ttre modulator
to sweep the delay tine up and
down. Typically the rpdulator
IflUIH is
set at
maxinum in
order to
produce
a
broad srreep and
the
npdulator
SPED is
set at a npdest value
(e.9.,
between 7:00
and
9:00
orclock) so
that
ttre conb filter
stneeps up and
down
every
few
seconds. A
high
setting of the npdulator
SPEED
would
sreep
the
notch
trnttern
over ttre
musical
spectrum too rapidly for
the
changing
harnpnic
structure of
the
music
to be heard and
might
also
cause
audible
pitch
vrcbble
of ttre
musical signal itself.
You
strould exlnrfurent to find ttre settings
of DELAY,
WIDIH, SPED
and
mixing ratio
which
yield
interesting
flanging effects
with
various
vocal
and instrumental
sounds. rn
general,
higher-pitched
sounds
work
best
with
shorter
delays.
FI,A}GIIG
WIIIT
FEMBACK
rlixing the dry and delayed signals at approxinately
ttre sare
level
causes corb
filtering
(a
trnttern
of nu11s and
peaks
in frequency
restrrcnse).
l,lodulation
of the delay tire causes ttre
trnttern
of
13
C.
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