OK, I understand now, the JBL literature gracefully explained the reasoning behind conjugate circuits (level the impedance out throughout a speakers range) and the bypass caps (allow fast transients through smaller caps without the delay of charging the bigger ones, thus affecting the music). I'll bet the battery is for "pre-charging" the big caps to a certain static or preset level to get rid of the charge-up time period. Am I correct in assuming this?
Tha capacitors charge and discharge in a non linear rate as they cross the 0 volt level. This is called hysteresis, and it causes distortion of the signal. By charging them with a battery, they remain biased to above 0 volts, never crossing, and this eliminates that diistortion.
Some people claim to be able to hear the negative effects of the battery in the circuit. Fortunately my hearing isn't that good so I can enjoy the positive benefits of biasing without any of the negative benefits.
I have a question. Do the caps like Mundorf with their double windings also get rid of hysteresis and if so does it do it better than the charge coupled, or are we talking about two different things here?
OK, I get that part, but does an input signal being a sine wave and going from positive to negative voltage, still react to in a linear fashion with the cap biased above (or +) zero volts? I'm thinking sinewave crossing from positive to negative and back again across the zero volt level. If the cap being positively charged behaves differently than a non-charged cap, than I'll accept that, I'm just not sure I understand the mechanics of it with a sinewave input going through it. Or is it a current related issue?Originally Posted by Don C
I'm not sure that I understand your question, but I'll make an attempt. The whole idea, as I understand it, is to make the capacitors react in a linear fashion. The caps pass AC signal (music) while blocking the DC component,(from the battery) so the DC bias does not appear at the input to be seen by the amplifier nor is it passed to the speakers. The only place that the DC bias is seen is right at the capacitor where it is applied. It does not affect the AC part of the signal passing through the cap, except to make the output look more like the input than would normally be possible.
Thanks for the excellent explanation. I definitely have a better understanding and from the links to Techbots workup on Bypass caps, I'm going to be modifying the L-150 X-overs again.
Giskard,
Your pictures of the networks makes me wanna get right to building a pair of my own. Really awesome! Have You auditioned them yet?
Will You also post a network layout?
Regards: Jakob
Great looking network. Now I am going to have to redo my L212 networks, the ones I did 2 year ago don't look THAT neat, or charged coupled.
I'd have to think about that. The whole endeavor didn't go as planned. The thread was going to be fancy and the networks were going to be fancy. In the end I redid the networks a second time basically from scratch with a more utilitarian perspective and I didn't take nearly as many pictures or notes as originally planned.
Could I talk you into trying a modified 3113B network before you go to the trouble? Would you care to A/B a pair of those networks with your stock N212 networks and see which you prefer?
I'm for trying anything that will improve an already great speaker.
Actually, I might have as many as 3 different networks overall in the 7 L212s.
The 3 I built have bypass caps, then there is the original pair and then there's the pair I bought last Sept. and they might have a different xover(haven't looked) being they have the foam inserts glued to the inside of the grille cloth that the originals don't have.
The 3 with the bypass caps are on the front and the other 4 are being used as surrounds, so I really haven't done a direct comparision. But I do know that the mirrored imaged boxes produces a better soundstage, and the bypass caps seem to make them more dynamic. I still haven't gotten any polystyrene caps for the 066, that from what I've read, should make them more airy.
FWIW, for HT, more subs are better. I'm using 3 12" subs, connected via speaker wire, to the center and side surrounds and the pair of 1500s connected to the HK 635 subout. I only use the 1500s when listening to music.
Ok, PM me with your address and I'll get a pair of old 3113B networks out to you to try. They aren't charge coupled (we can talk about that later) so you should be able to get a decent idea how they compare with the stock N212 networks.
My only reason for suggesting this is because I think the 3113B or N96/N112/N150A do a bit better on DVD/LaserDisc playback than the N212 or N110A networks do.
Agreed.
Please, pretty please!!! It would spare me and others a great amount of time and work. I think they look great, and the design really deserve to get spread via the forum.
Thanks: Jakob
How do the new networks compare to the old?
As soon as my shop is done, This will be one of my first projects "Changing from L250's to 250Ti's"
Shane
The thread that has the reviews and the history behind this whole project is below. I started the thread two years ago and it's officially done (for me at least) now. As you can see, I did finally relent and decide to pursue upgrades although I was very happy with the L250's as they were.
And the solution was - as Giskard predicted - charge coupled networks. Custom, bi-wireable, adjustable charge-coupled networks actually
http://www.audioheritage.org/vbullet...read.php?t=289
jblnut
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