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More Crossover Design
The crossover design is rather simplistic expected fare one would expect for a budget
project, but this did not compromise the design, as this is all that was required to obtain
my goals.
In all variations, the woofer crossover is a 2nd order electrical topology providing
roughly a 4th order Linkwitz Riley acoutstic transfer function at 3450 Hz. The tweeter is
3rd order electircal, and providing a reciprocial 4th order LR function.  The impedance
minima is 3.5 ohms, so we must consider this a 4 ohm design. The phase plot shows
good phase tracking as well.

Impedance Compensation
Another option I've not offered on a speaker design before is an impedance leveling
network. Not unusal in a crossover design, the LP and HP sections sum to a impedance
of nearly 50 ohms below the crossover frequency. This will result in response variations
when driven by higher output impedance tube amplifiers, The circuit shown below is a
notch filter to linearize the impedance without affecting the speaker acoustic response  
This is accomplished by installing the network before the crossover.  While this can
make for a significant improvement when connected to tube amplification, it will provide
no benefit at all if the speaker is driven by a low impedance solid state amplifier.     The
additional components will run you an additional ten bucks per speaker, should your
needs deem it necessary to include it in the design.
Note the BOM shows the 2.5 ohm resistors as 2.4 ohm. Use what you have, as it will
make little if any difference. The 2.5 ohms are available at MAD.
Acoustic Response
Impedance
System Phase
Response
Close up of the
responses of the 3
crossover variations
Original/Current
Crossover Network
Optional
Crossover
Network
Impedance
Compensation
Network
Enclosure Drawing
Bill of Materials
Original Crossover
Woofer:
L1011 1.2 mH P-core p/n 255-102
(original was 1.15 mH)
C1021 15 uF p/n 027-934
Tweeter:
C2011 3.9 uF p/n 027-022
L2021 0.15 mH 18 ga p/n 255-206
C2031 10 uF p/n 027-932
R2041 2.4 ohm p/n 004-2.4
R2051 2.4 ohm p/n 004-2.4
Revised Crossover
Woofer:
L1011 1.0 mH p/n 255-100
(steel laminate or P core)
C1021 20 uF p/n 027-436
Tweeter:
C2011 4.3 uF p/n 027-419
L2021 0.15 mH 18 ga p/n 255-206
C2031 10 uF p/n 017-932
R2041 2.4 ohm p/n 004-2.4
R2051 2.7 ohm p/n 004-2.7
Impedance Compensation
R0021 6 ohm p/n 004-6
C0021 20 uF p/n 027-436
L0021 0.25 mH 20 ga p/n 255-026
Drivers
Hi-Vi B3N PE p/n 297-428
Dayton ND20FB PE p/n 275-030
Listening Impressions
These work well as computer speakers or in a small HT setup. They have a surprising amount of bass
if placed closer to the wall.
Copyright 2007 Wayne Wendel and Curt
Campbell
Free for non-commercial use.