Le 18/12/2024 à 15:00, kandoit7 via
groups.io a écrit?:
Hello,
everyone.
I
am someone who has been receiving a lot of help from this
community.
Recently,
I have been studying microphone output impedance.
?
I
noticed that there are various terms commonly used, such as
"output impedance" and "symmetrical impedance."First
of all, I am confused about the definitions of these terms.
?
Can
I assume that the two terms mean the same thing?
Not really. Symmetrical impedance is not a concept.
A connection? (input or output) can be symmetrical. An impedance is
a ratio between voltage and current. It does pot pertain to the type
of connection.
?
From
what I understand:
- "Output
Impedance" refers to the impedance between Pin 2 and
ground on the microphone.
- "symmetrical
Impedance" refers to the impedance between Pin 2 and Pin 3
on the microphone.
?
If
that is correct,
It s not correct.
I
would like to know whether the impedance values provided by
manufacturers refer to output impedance or symmetrical
impedance.
The impedance value the manufacturer specifies is the output
(source) impedance between teh points that are used to drive the
subsequent stage (usually a mic preamp).
Since the input of the preamp can use any type of connectors,
numbers are meaningless.
The only thing that matters is the points that are used for
connection. E.g. for a 1/4" jack, these points would be Tip (hot)
and Ring for a balanced connection, but would be Tip and Sleeve
for an unbalanced connection.
The relevant impedance is across the balanced connection (across
pins 2 and 3 for XLR connections).
?
Secondly,
I have a question about the method for measuring impedance.
?
From
what I have studied, among the XLR pins (GND-1, HOT(+)-2,
COLD(-)-3):
In
the case of measuring condenser microphone impedance using
voltage drop, should I connect the load RL between Pin 2 and
Pin 3 to calculate the impedance?
Or
should I connect separate loads RL between Pin 2 and ground,
and Pin 3 and ground, to calculate the impedance? Which method
is correct?
The first one.
In order to measure the voltage drop, you need a constant
acoustic source. Do you have it?
Beware that some mics have a very low output impedance (e.g.
Schoeps).
Loading them for 6dB attenuation may very well make them clip,
which would give a false reading.
