The OFFICIAL JBL Owners Thread - Page 520 - AVS Forum
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Originally Posted by gferrell View Post
So what are the principals of a bias XO? How do you go about doing it?
Go over to www.lansingheritage.org
Search for Charged-Couple Networks.

What it involves is changing the caps. Lets say the tweeter circuit has an 8uf cap and a 4uf cap.
The 8uf is replaced with two 16uf caps, wired in series.
The 4uf is replaced with two 8uf caps, also wired in series.

You do the same for all caps.

The common points of each pair of caps are connected to 2 megohm resistors.
The other ends of the resistors connects to the + side of a 9v battery.

This does two things, the 9vdc keeps the layers of the caps tight.
And it also keeps the audio signal above the 0 volt line.
W/O the 9v charge, the layers tighten, loosen, tighten, loosen as the frequency and amplitude change. And by keeping the signal above the 0 volt line the caps are always on, eliminating a slight phase sift as the signal changes direction.

As you can see, both the doubling of size and number of caps will require a lot more space. The original L212 XO fit on one 4.5 x 7 card. The Biased XO required 3 cards, one for each driver.
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