SEOS12 with Designer10 Woofer

Ok, here is the final on the SEOS12/Designer10 crossover design. This worked out pretty sweet. I ended up dropping the crossover point down to about 1kHz, using roughly 6th order acoustic on the tweeter and 3rd order on the woofer. This smoothed out the response in general and still gave excellent polars.

First, here are some curves. Horizontal:

Horizontal "map" format:


Vertical (I only did +/-15 and +/-10 degrees for this, which shows it is doing as intended):


The woofer and tweeter responses separate and combined:


This is the measured impedance of the system:

It gets a little low around 1800Hz, but shouldn't make any amp that could handle 4 ohm speakers uncomfortable.

And here is the crossover schematic. This is a pretty sophisticated crossover, with some tricks I'll explain in a minute.

First thing you'll probably notice is that there are a lot more parts across the tweeter. I got spoiled using the PEQs that Mini-DSP provides for smoothing response peak bumps, so I used the 'shallow notch' sections shown (circled in green below). A design could be done without these, but it wouldn't be as smooth.
The part outlined in red is essentially the Parham/Zilch configuration.


Circled in blue (around L2) is a trick that does a couple of good things. The capacitor C4 resonates with L2, putting a notch where the woofer's breakup resonance might otherwise interfere. It also makes L2 act like a larger inductor near the crossover frequency, which lets us use a smaller valued part (less expensive, lower series resistance). The downside is that at still higher frequencies signal can sneak around L2, limiting the ultimate rolloff to the woofer. Resistor R5 keeps the tradeoff reasonable (and the woofer's greatly reduced response so high in frequency also helps). Unfortunately, PCD is unable to exactly model this arrangement, so I modelled it as a parallel RLC network instead and checked it out with real hardware.

The schematic, by the way, was drawn using the tool at the free website www.circuitlab.com. You can go look at my schematic there by using this link - https://www.circuitlab.com/circuit/qd2vbu/seos12designer10-xover/. CircuitLab is a pretty nice circuit modeler (not just a schematic drawing tool), but it can't be used to simulate the crossover since it doesn't allow for driver FRD or ZMA type files in the simulation....too bad.

Here is a Parts List and some notes on the design:
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SEOS12/Designer10 Notes and Parts List

Woofer = Dayton DS270-8 (cabinet alignment will not affect crossover)
Tweeter = any of: B&C DE250; Denovo (Erich's) "better" driver or his"lower cost" driver
Waveguide = SEOS12 (plastic, fiberglas, or 'solid surface')

For tests, woofer was centered 9.75" below waveguide center, woofer and waveguide both front-mounted on same baffle plane. Baffle is 16" wide. Measurements made at distance of 30inches, 9 degrees above tweeter's baffle position.

Crossover Parts: using reference designations from the circuitlab schematic at
https://www.circuitlab.com/circuit/qd2vbu/seos12designer10-xover/

C1: 20uF Film capacitor (Parts Express# 027-436)
C2: 1.5uF Film capacitor (PE# 027-412)
C3: 40uF capacitor (PE# 027-442....or: 027-350 in parallel with a 027-336 will also work here)
C4: 2.2uF Film capacitor (PE# 027-415)
C5: 10uF Film capacitor (PE# 027-428)
C6: 3uF Film capacitor (PE# 027-418)
L1, L3, L4: 0.56mH inductor, series resistance = 0.5 ohm (PE# 255-232)
L2: 1.5mH inductor, series resistance <0.35 ohms (PE# 266-552)
R1,R6: 2ohm 5W resistor (PE# 015-2)
R3: 8 ohm L-Pad (PE# 260-248 or 260-250)
R2: 15 ohm 5W resistor (PE# 015-15)
R5: 5 ohms 5W resistor (PE# 015-5)
R7: 3.3 ohms 5W resistor (PE# 015-3.3)

Nominal setting for the L-Pad: set for 4.7 ohms between the tweeter [+] lead and the top of the L-Pad (where it connects to C2), tweeter connected in the circuit.
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A zip with of all the design files is at
http://libinst.com/SEOS/SEOS12+Designer10/Xover%208.zip