The original mod can be seen HERE

This revision was initiated after a conversation with Jeff in which he expressed his desire to keep it as simple as possible while adhering to the original design so as to simplify restoration back to the original design.

Admittedly, the previous mod resulted in something other than a W70.  Chambering the ten inch unit was very difficult due to lack of space on the front panel. The use of a six inch unit further deviated from the original but the original front panel can be maintained.

This mod does deviate from the original but in a smaller manner.  Change one crossover component and add two. See fig 3

The test setup.  Note the vent, originally a 3" diameter tube made into a 2" diameter tube with rolled magazines.

Close-up of the crossover, such as it is.  The original comprised of the 4mh coil and a 3.3uf capacitor in the tweeter line along with a 50W potentiometer.  The 10" acts as a full range in parallel with the woofer and its 4mh coil.

The modification comprises adding a 0.5mh low pass filter in series with the 10" to attenuate the highs above about 6khz.  The tweeter capacitor was changed to 1uf, filtering the highs to the tweeter starting around 9khz.  This removed the 7db rise between 3khz and 5khz (see fig 2)

Z RED=without pot and 0.5mh coil in ten; BLK with pot at 2 o'clock and 0.5mh coil

RE: the BLACK trace.  The tweeter circuit is unimportant here.  The point is to show the higher impedance of the 10" with the added 0.5mh coil. The rise due to the 50W pot and the coil is about 2 ohms as can be seen below 200hz.  This includes the 0.33W of the added coil.  Keep in mind that this impedance reflects that of the 10" in series with the coil and the 50W pot and this series triad is in parallel with that of the 12" unit and its series coil.. (se fig 3)

At this low frequency, 150hz, the effect of the tweeter is essentially non-existent due to the 1uf high pass filter

As the impedance increases with frequency, the output decreases

Click on image for a larger view

1w1m W70 RED=orig; twt 3.3uf, pot 3 o'clock, twt polarity normal

The following all have the 5mh low pass filter

YEL=pot for 10" at 2 o'clock, twt pot full CW;

BLK=10" pot full CW; twt pot at 2 o'clock

The notch at 7khz refused to go away regardless of my attempts, which included reversing the tweeter polarity, the latter exacerbated the notch.  It did, however, move up where it would be possibly less noticeable.

Click on image for a larger view

NOTE:  There appears to be a black trace superimposed on the yellow.  This was the result of checking my returning the system to the previous setting.  

Click on image for a larger view

The modified crossover.  The original comprised of the 4.5mh low pass filter, a 3.3uf high pass filter for the tweeter and the associated 50W potentiometer.

The mod, as seen here, has the added 0.5mh low pass filter in the 10" circuit along with the associated 50W potentiometer.  The 3.uf high pass filter has been changed to 1uf.

All speakers maintain normal polarity.

The numbers 1,2 & 3 refer to the potentiometer connectors as shown in the top view diagram.  This configuration allows the level to be increased during clockwise rotation of the pot.  By reversing the wires to pins 1 & 3, that configuration is also reversed.