Crossover design is the most artistic part of speaker
design. Any set of drivers with an enclosure will work with many
different crossovers. For this system I tested 4 completely different
crossovers, all of which had good looking frequency response charts
and all of which had specific pluses and minuses. The general methodology
- Ensure that you have actual impedance and on-axis
frequency response datasets for all of the drivers in the system.
The on-axis response should be stored in the "frequency response"
part of the driver properties. If you merged a port and nearfield
and on-axis response that works also.
- Create a network (crossover piece) for each driver.
I name mine Woof and Tweet, usually. Start with the woofer and
tweeter in each network.
- If desired, add impedance compensation to the woofer
(the tweeter rarely needs it).
- Calculate frequency response and impedance for
the resultant circuits.
- Create goals for the woofer and tweeter circuits
based on your desired crossover point and slope. I usually use
an absolute value for the goal value based on eyeballing the woofer
and tweeter response.
- Insert stock crossovers for the woofer and tweeter
using the same frequency points and slopes.
- Use network optimize to get optimum networks for
- Create a new network using all of the speaker drivers
and copy/paste the networks from each indivudal into that. Calculate
that frequency response, using the correct offset for the drivers.
- Tweak the final crossover.
Here's one crossover I did using 4th order Linkwitz-Reilly.
It sounded good and measured well. I also tried creating
a third order butterworth. That turned into this
Finally, I built a third order butterworth without
impedance compensation, based on seeing that the impedance rise
is mainly after the crossover point. That turned into this
This crossover actually tested very close to the 4th
order Linkwitz-Reilly, is much simpler, sounds good, and uses way
fewer components so this is my final crossover. The measured frequency
response of the system is ±1.5dB from 40Hz to 20KHz.
The woofer circuit induces some droop in the low frequency
response. This compensates for the baffle step. Baffle step is a
6dB rise in response caused by the front baffle size. At low frequencies
the sound wraps around the speaker - producing sound in a 360 degree
arc. At higher frequencies the sound radiates towards the front
- a 180 degree arc. Thus, at higher frequencies you get a 6dB increase
(doubling) of the forward facing sound. This will be measured acoustically
when you do an on-axis measurement, although since some of the low
frequency sound gets bounced and reradiated I think it may be an
overstatement of the audible change. Nevertheless the woofer crossover
here does compensate for the baffle step - producing a very smooth
measured on-axis acoustic response.