General
Comments (for best results with series cross-overs)
The whole aim
of this implementation of series cross-overs is to provide a very
reasonable sound quality with just a few components, no design
software, and minimal measuring equipment, and little or no driver
correction.
Because of the
self balancing nature of the series cross-over the values given
will generally give quite good sounding 2-way loudspeakers.
If you are after
an absolutely flat response, you will have to make sure
that you have software and measurement gear that can carry
out optimisation of the cross-over network.
Due to an increased
interest in series crossovers, there are now several software
packages that can model them.
Driver
Requirements and basic "rules"
For best
results for a first order series crossover, driver
should be well behaved and flat over the
range over which they will be operating.
You
have to remember that we are not going to make any
attempt to compensate for driver problems.
Tweeter
should have a smooth taper at its lower end and
response should be smooth and flat for most of
its operating range. It should also be capable
of withstanding a bit more power at lower frequencies
than your normal tweeter.
The
cross-over point with preferably be between
2.5 and 3 times the resonant frequency of the
tweeter.
The
mid/woofer must be smooth, without any major
dips or peaks, at least up to this value,
and must have a smooth roll-off and no distortion
problem in its higher frequency response range
A
case or 2 in point: The vifa PL18WO has
a reasonable peak in the 700-1000 range,
which makes it difficult to manage with
a series cross-over, also, it gets harsh
if you try to cross at much more than 2500Hz.
Similarly, some of the metal cones tent
to "ring" once they get much above
about 2000Hz, and since we are only cutting
at about 9dB/octave (zeta .707), it is very
difficult to work a 1st order series with
this type of driver.
Some
of the best drivers for use with the series
cross-over tend to be paper and poly cones.
If you want to use metal cones, then I
advise using a parallel cross-over.
If,
on implementing a series cross-over,
you notice a bit of harshness, just
try dropping the cross-over point
a bit lower or adding a zobel to stabilise
the woofer impedance. So long as you
stay at more than twice the resonant
frequency of the tweeter, the tweeter
will generally not have too many problems
except at very high volumes, just
make sure you are using as low DCR
coil as you can find.
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