The frequency response
of a microphone,
a speaker
or a pair of headphones
describes
how the device responds
to various frequencies.
Looking at the frequency
response of a device
helps us understand
the effect that device
has on the frequency
balance of signals
passing through it.
It gives us insight
into the difference
between the frequency
balance of the signal
at the input of the device
versus the frequency balance
at the output of the device,
In addition
to showing us
the frequency range
that a device is capable
of passing,
frequency response
also illustrates
the relative level
of each frequency
across the spectrum.
This graph shows frequency
on the x axis
from 20 hertz to 20 kilohertz
and level
on the Y axis
in decibels or DB.
Let's say
we send a perfectly
balanced signal
to the input of this device
where each frequency
is equal in level.
If the device has no impact
on the signals
frequency balance whatsoever,
the frequency
balance
at the output of the device
would also be
perfectly balanced.
That would mean
the device
has a perfectly flat
frequency response
and would be represented
on this graph
with a perfectly flat line.
On the other hand,
if the device did alter
the frequency
balance of the signal,
the frequency response graph
for that device
wouldn't be a flat line.
It would instead show
where the device
attenuates or reduces
the energy level
at some frequencies
and where it boosts
the energy level
at other frequencies.
I like to think
of the frequency
response graph
as the IQ curve of advice.
Any signal
passing through
the device will be subject
to that frequency
response curve,
which can be a good thing
or a bad thing
depending on the situation.
When comparing the frequency
response of different devices,
it's important
to consider the purpose
of the device and the role
it plays in your system.
Sometimes flatter
isn't necessarily better.
For example,
if I'm choosing studio
monitors, headphones
or indeed a converter
for mixing music,
I'll probably look
for something with a very flat
frequency response.
That's
because I want something
that alters the signal
as little as possible.
Otherwise,
I may make mixing decisions
based on the frequency
response of
my listening system
rather than making decisions
based on the actual frequency
balance of the signal itself.
In other situations,
that doesn't have a flat
frequency response.
Maybe I'm choosing
a microphone
that will help me capture
a particular sound
for a particular instrument.
One example of
this is the Shure
B2 52 microphone
that has a frequency response
uniquely tailored
to recording kick drums.
Again, I find it helpful
to think of the
frequency response
as the IQ curve of a device.
I might want a device
as the IQ curve of a device.
So if I'm
choosing a microphone
that will help my vocal cut
through the mics
at a live show,
I might choose a mic
with a subtle boost
in the high mids or highs
if I want to mix,
that will tame
the sound of a
guitar amplifier.
I might choose
Mike that has
a smoother spots.
So how do we measure
frequency response?
Well,
one way to do
it would be to send
a test signal into a device
that contains every frequency
throughout the audible
spectrum
and measure
the output of the device.
This will help us understand
the transfer
function of the device
or the effect
that the device has on
the signal.
Let's set up a test
that demonstrates
this process.
I'll be using a software
called Crucis
that's used for custom
programing and audio DSPs.
You could measure
the frequency
and the output
of our device under test
and can draw a comparison
between those two
and represent
the difference on. A graph.
There are a few factors
I'd like to share with you
that might affect the results
of a frequency
response measurement,
especially a measurement
that takes place
in an acoustic environment.
The first factor is
the directionality
of the microphone
or speaker being measured.
The specified frequency
response of a microphone
or speaker
is generally describing
the on axis response.
This means that
the frequency response
may vary
if the microphone or speaker
is pointed
into a different direction
relative to the source
or the listener.
Microphones
tend to sound darker
when recording sound sources
that are off axis.
Likewise,
a speaker will sound darker
to a listener
whose off axis
to the high frequency driver
than it will to a listener
who sits
directly in
front of the speaker.
The second factor is
the proximity effect.
When using a
directional microphone,
you'll experience
a bass boost as the microphone
gets closer to the source.
This,
of course, affects
the frequency response
that you can expect
from that microphone.
I created a video
that goes into much more depth
on the proximity effect.
It is a fascinating concept,
so I'd recommend
watching that video
if you're interested
in learning more.
The third factor
I want to share with you
is the fact that
every element
of the signal chain
will have
a frequency response.
That's why it's so important
to set up tests
that isolate
the particular device
you're testing.
For example,
measuring a microphone's
frequency response
by blasting a test signal
through a low quality speaker
into an acoustically
untreated room
will not yield
accurate results.
The results
will not only include
the frequency
response of the microphone,
but also the frequency
response of the speaker
and the frequency
response of the room itself.
Everything has a
frequency response
and our goal is to be as aware
as possible of the effect
that each component
within our system has
and use that knowledge
to achieve
the desired results.
One of the biggest
obstacles is holding
you back
is probably the frequency
response of your room.
So I'd recommend
watching this video
that will show you
how to optimize your room
for critical
listening and recording.
I'll see you over there.