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LE15-Thumper
05-25-2005, 08:30 PM
For a local theater job. Tempered masonite sure does a nice job. All the connections are point to point underneath. Just put a 3/4 block under each corner for mounting clearance. Those solen parts are purdy, ain't they ?

John W
05-26-2005, 09:08 AM
Great job with your crossover. What did you use to tie things down with? Are these zip ties with screw holes?



I ordered the parts for an N333 crossover network, like is found in this thread:

http://audioheritage.org/vbulletin/showthread.php?t=166&highlight=l300+charge (http://audioheritage.org/vbulletin/showthread.php?t=166&highlight=l300+charge)

I am building the charge-coupled version..

I have heard that the inductors can interact with each other. How strong is this interaction and are there guidelines for inductor placement? Some of the JBL crossovers are all contained within a box, how does that work? :blink:

Anything else I should consider when putting this thing together?

LE15-Thumper
05-26-2005, 10:39 AM
Great job with your crossover. What did you use to tie things down with? Are these zip ties with screw holes?



I ordered the parts for an N333 crossover network, like is found in this thread:

http://audioheritage.org/vbulletin/showthread.php?t=166&highlight=l300+charge (http://audioheritage.org/vbulletin/showthread.php?t=166&highlight=l300+charge)

I am building the charge-coupled version..

I have heard that the inductors can interact with each other. How strong is this interaction and are there guidelines for inductor placement? Some of the JBL crossovers are all contained within a box, how does that work? :blink:

Anything else I should consider when putting this thing together?

Yes those are screw mount wire tires. And I also used some sticky mount wire tie fasteners for some of the smaller caps.
As for proximity of the inductors, I really don't know. Some of our other more "learned" members out there may have the answer. Giskard, Zilch, Boputnam, etc...
Good luck on the charge coupled version. It should sound pretty nice.

4313B
05-26-2005, 10:43 AM
3" apart seems to be the consensus. Set at right angles to each other too.

Zilch
05-26-2005, 12:10 PM
All of the crossovers I've built have had separately ampable HF vs. LF sections, my preferred operating mode. By chance, I discovered I had crosstalk in my DIY 4430 crossovers, i.e., the HF compression driver played (albeit minimally) when the HF amp wasn't even on, and the LF was playing into an 8-Ohm dummy load. I use this method to check them all when making them now.

To find the optimum location and orientation, I connected the large LF coil using 8" leads and moved it around listening per above. The inductive coupling to the coils in the HF section is immediately apparent. The answer? What Giskard said. 3" apart and oriented at right angles.

Remember the drawings of magnetic fields around coils from high school physics? The main action is concentrated at the ends (faces) of the coil. It's THAT portion you want to be sure is aimed away from other coils on the board, and the differences are substantial. Try it yourself to confirm.... :)

John W
05-26-2005, 12:57 PM
Actually, I think I slept through high school physics. :o: But I found this neat illustration on the web.

spkrman57
05-26-2005, 12:59 PM
Makes it easier to comprehend!

Ron

hector.murray
05-26-2005, 08:45 PM
I seem to recall in another thread not long ago talk of a Mu metal shield around the coils. Is this an effective way to reduce this type of interferance and is it indeed worth it?

LE15-Thumper
05-26-2005, 10:27 PM
Set at right angles to each other too.

How do you put round coils at right angles to each other ? I am a bit slow today :o:

Zilch
05-26-2005, 10:50 PM
The axes of the coils, vertical in the illustration above, should be perpendicular to each other.

You've got 3 planes to work with.

Mu metal is expensive. Inches are cheap....

LE15-Thumper
05-27-2005, 12:08 AM
The axes of the coils, vertical in the illustration above, should be perpendicular to each other.

You've got 3 planes to work with.

Mu metal is expensive. Inches are cheap....

Are you saying I should stand these Air Coils up like a wheel ?
Because laying flat isn't the field circular ?

Zilch
05-27-2005, 01:46 AM
Envision that the coils are wheels, and the air cores have axels in them. The axels are actually electromagnets created by the current flowing in the coils. Whether the axels are there or not, the electromagnetic fields are, and their axes are oriented the same as the imaginary axels.

To minimize inductive coupling between the coils you want the axes (axels) pointing perpendicular to one another. Thus, if you have one coil laying flat, with its axis pointing perpendicular to the board, you'll want the second coil standing up like a wheel, yes, and at maximum practical distance away.

If you have a third coil which you don't want to couple to either of the other two, it would also be standing up, but with its axis at right angles to the second one.

Finally, if possible, don't point the axis of one coil at another coil. The electromagnetic fields are strongest on axis, where the electromagnetic poles are, not at the circumference of the windings.

While there is some inductive coupling between two coils laying side by side as you have shown, it is much less than would occur if you had stacked the coils on top of each other, i.e., with their axes in alignment. Better yet, though, would be if one of them were mounted on edge, standing up like a wheel, with its axis pointing away from the coil laying flat. In your photo, the axis of one of the coils would point left to right. Ideally, it would also be separated from the other coil by several inches.

O.K., Pop Quiz, then. Accordingly, how might I improve my "Quick and Dirty" crossover coil layout here:

[Thumper only answer, please.... ;) ]

glen
05-27-2005, 02:02 AM
Are you saying I should stand these Air Coils up like a wheel ?

That's what Lansing was doing in 1939 for their Iconic.

In the photo below there is one coil on the right, seen edge-on.
Second coil in the middle is rotated 90 degrees so you can see it's circular silhouette.
Third would be mounted flat on the base as yours are (neat job!)

These are mounted closer together than would be recommended today.

photo from an ad here on the site:

http://www.lansingheritage.org/images/lmco/advertizements/1939cat-1.jpg

You notice that in the animated diagram in the earlier post the magnetic field expands and collapses, mainly in one plane, as current is applied and removed (or reversed, as in a crossover).
The moving magnetic field will create an electrical current in another coil mounted in the same plane if it is too close.

The axis in which a coil generates the greatest expansion and collapse of the magnetic field is likewise the axis along which the coil will most efficiently convert a moving magnetic field into electrical current. So mounting a coil oriented 90 degrees different from it's neighbor will reduce it's sensitivity to it's neighbor's magnetic field.

LE15-Thumper
05-27-2005, 12:26 PM
OK Zilch, I would take that small coil in the bottom left of the pic and turn it 90* or take the the top left coil and stand it up and turn it 90* :dont-know

Anyone remember the left hand generator rule ?

Zilch
05-27-2005, 12:53 PM
Yup, the little coil at the bottom should be turned 90 degrees to comply with the guidelines, though it's far enough from the others not to matter, probably.

Standing the upper left coil up and rotating it would aim it at the big coil, probably not a good move.

The big LF coil is the major concern, since it has the largest currents and generated field. It's a little closer to the one on the upper left than I might desire (2-1/4"), but there's no discernable crosstalk since I rotated it into its present position. It was originally aimed left to right there, and the HF played with no amp connected.

I'll make the change you recommend and be good to GO! :bouncy:

Here's a current JBL crossover from the AE Series. I don't know what guidelines apply to laminate-core inductors, never having used them, but for the most part, they're at right angles to each other:

Mr. Widget
05-27-2005, 12:57 PM
I typically do orient my inductors at right angles to each other, but with such large coils and given the fact that you seem to have the real estate, why not do this?

Widget

LE15-Thumper
05-27-2005, 04:17 PM
I typically do orient my inductors at right angles to each other, but with such large coils and given the fact that you seem to have the real estate, why not do this?

Widget

All I need now is a "Cut-Copy-Paste" soldering iron :p

LE15-Thumper
05-27-2005, 04:58 PM
Standing the upper left coil up and rotating it would aim it at the big coil, probably not a good move.

Wouldn't it be at 90* to the big coil though ?

Zilch
05-27-2005, 05:40 PM
Yes, in the same way as your proposal for the smallest coil.

BUT, in this case, the axis would be aimed at the side of the largest coil. There's field there.

In the case of the smallest coil, it'd be "aimed" into empty space.

The aiming is a secondary factor. Try it yourself as I have suggested above. You can easily determine the relative influence of location and orientation of coils in your layouts by listening as you move an active coil around....