Mike
The curve shows 7.5 ohms 500 Hz to 5k Hz. This is a critical number, and is the design load impedance for the low pass filter.
C1 to C5 also L1 to L5 are calculated from this value along with the delay time. The next step is to build a lows pass filter and check the delay.
I have enough spares to bread board so you can test it with your 604.
PM me your shippiing address full name and phone number.
Please verify your test set up with an 8 or 10 ohm resistor.

Don