Today I finished designing my crossover. Here’s what I have come up with.
I have to give a special thanks to DIY Audio and Video.
I’m building a speaker for an old radio that, in addition to a new loudspeaker, I’m creating a cool new case. It’s not a stereo, so I just need one loudspeaker.
Here’s what I’m using for speakers.
A Dayton 8inch 100watt woofer. You can check it out here. The specs for this woofer are here.
The tweeter is a 100watt Goldwood GT324. You can check it out here. You can read the specs for this tweeter here.
The woofer is an 8 ohm speaker with a frequency range from 29 Hz to 3,000 Hz. The tweeter is also 8 ohm, but with a range of 2,000 Hz to 20,000 Hz.
The woofer’s maximum decibels is 88 db and the tweeter’s is 96 db. Using an lpad circuit, I plan to pull that tweeter down to 88 db to match the woofer.
And to calculate a proper Series Notch Filter, I need the free air resonance of the tweeter, which 1,800 Hz.
The Crossovers
So based on this tutorial, I came up with the following two crossovers.
For the tweeter, I’m going to create a 3rd order Butterworth 800 Hz crossover. For the woofer, I’m going to build 1st order Butterworth 3,000 Hz.
Those are the crossovers, now I need a Loss Pad circuit. A lpad circuit, or driver attenuation circuit, is supposed to decrease the output levels of the louder speakers to match the output of the more quiet speaker.
In my case, the tweeter outputs up to 96 db and the woofer is 88 db, so I need to pull the tweeter output down 6 db.
A lpad is two resistors, one in series and one in parallel.
Using the fabulous DIY Audio and Video lpad calculator, here’s the circuit for the tweeter. I entered the values 6 db, 100 watts and 8 ohms.

Parts List
Resistors
R1 = 3.99 Ohms 49.88 Watts
R2 = 8.04 Ohms 25 Watts

The last thing to do is design the Series Notch Filter.
I’ll be honest, I’m not sure exactly what this one is for, but the purpose of this filter is to block frequencies within a certain range, letting through all others.
To build the series notch filter, I’m using the free air resonance (Fs) of the tweeter, which is 1.8 kHz.
Using the awesome Series Notch Filter Calculator at DIY Audio and Video, I was able to determine the necessary components.
Re = 8 Ohms
fs = 1800 Hz

Parts List
Capacitor
C = 16.68 uF
Inductor
L = 0.42 mH
Resistor
Rc = 8 Ohms 
The last step to do, which I haven’t done yet, is to combine all of these circuits into one. I’m going to sketch it out on paper. Then I’ll pull my parts and prototype it on breadboard.
Stay tuned.
Parts List
 3rd Order Butterworth (Tweeter)
 C1 16.58 uF
 C2 49.73 uF
 C3 33.16 uF
 L1 1.19 mH
 L2 2.39 mH
 L3 .8 mH
 1st Order Butterworth (Woofer)
 LPad
 R1 3.99 Ohm 49.88 watts
 R2 8.04 Ohm 25 watts
 Notch
 C5 16.68 uF
 L5 0.42 mH
 R3 8 Ohms