The implementation of parallel LCR
and RC circuits in crossovers
Copyright 2013 © Troels Gravesen
A very common question to my crossovers is why my layout differ
from schematics., i.e. why is the RC circuit turned up-side down or why
is the LCR circuit components in a completely different order.
The short answer is that
circuits parallel to the driver can be put together in any
order, being RC or CR or LCR, CRL, LRC, etc. They do the same thing
regardless of order.
However, they MUST be at the same
spot in the signal path! Do not move an RC or LCR circuit to the other
side of a series capacitor or series coil! Then terrible things will
An RC or LCR circuit in parallel to the driver can be implemented in
any order; it does the same thing: It absorbs energy at certain
frequencies being a harmonic oscillator in technical terms.
have a resistor connected between plus and ground it will absorb energy
in a magnitude dependent on the value of the resistor but regardless of
frequency. The energy will be turned into heat and the resistor will
If we have an RC circuit this all of a sudden becomes
frequency dependent, depending on the value of of the coil and the
speaker impedance it sees. The coil will pass lower frequencies and at
higher frequencies its impedance will rise steadily until infinite,
thus will not work in the e.g midrange and treble range (R2021/L2021).
My LSPcad software always places the components in a specific order but
when it comes to the actual crossover layout it may prove beneficial to
change the order due to size of the components or due to wanting to get
coils as far apart as possible to reduce interaction given the space
constraints of the crossover board.
Hope this helps :-)
Above the midrange section of the Jenzen-D
After the series capacitors we have an RC circuit
smoothing the roll-off of the midrange drivers towards lower
Below you can see the same crossover where the RC
circuit has been turned up-side down.
L2021 and R2021 turned up-side down.
Above is seen an LCR circuit, a notch filter, suppressing a peak in the
treble range of the middriver.
The values of the components are
tuned so that we have a smooth roll-off of the middriver towards higher
Below you can see the same LCR circuit in different order, e.g CLR
(from upside down) or LCR. It could also be LRC.
It does not matter.
It does the same thing regardless of orientation.