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Author Topic: New "crossover" schematic and diagram  (Read 58240 times)
Tre
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« Reply #150 on: October 09, 2013, 04:48:33 PM »

The Great Heil AMT is very complex.

Each Great Heil AMT is, in fact, two drivers, side by side and within each driver there are many sound sources. Each one a little weaker than the one next to it.

The pleat all the way to the left of the left driver (and the pleat all the way to the right of the right driver) moves the most. The one next to it (closer to the center) moves a little less and so on and so on until the ones closest to the center move very little.

This is because of magnet strength. The portion of the laminates over hanging the diaphragm on the left half start out thick all the way to the left and get thinner as they extend to the right toward the center of the diaphragm. More magnet strength, more movement. Ditto for the right, inverted. They start out thick on the right and get thinner as they extend to the left towards the center of the diaphragm. There is less and less output from each pleat with the outer pleats producing the most sound and the inner pleats producing the least.

Speaking about just the sound coming from the front of the Heil, that sound, as a whole from each side, does not travel perpendicular to the diaphragm but at a 22.5 degree angle toward the center (the sound from the left driver toward the center to the right, the sound of the right driver toward the center to the left) and meet at a point in the center and forward of the diaphragm. In fact the patent says a point not only in the center of the diaphragm but out in front of it, in front of the over hanging laminates and those sounds meet and form a line source and the higher the frequency, the thinner (narrower, left to right) that line source becomes.

Once you understand this I think you'll see that it is a bipole after all.

The pleats to the left of center squeeze together from their rest point on the positive half of the input wave form with each vertical wire run moving to the right but the outer most wire run moving the most (so that first pleat squeezes harder than the rest) and with each wire run closer to the center that movement is less and less until the one closest to the center is hardly moving at all. On the negative half of the input wave form the pleats widen from their rest positions with the outside pleat moving the most and the inside pleat moving the least.

The right half driver does the same thing, inverted.

The pleats on the back side of each of the two drivers (the left half and the right half) are doing the same thing at the same time.

Edit, This is very important. For the speaker to make a whole wave form, the pleats, on the first half wave (the positive half of the input), have to squeeze together FROM their rest point and then relax back to their rest point. Then each pleat, on the second half of the wave form (the negative half), have to expand from their rest point then relax back to their rest point.

The gif is correct except for the shape of the pleats (and that doesn't change the theory) and the fact that the magnetic poles have to be reversed left to right. For instance, north in front and south in back for the right half of the AMT and south in front and north in back for the left half of the AMT.

This thing fascinates me.

Tre'
« Last Edit: October 11, 2013, 04:53:46 PM by Tre » Logged
Tre
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« Reply #151 on: October 11, 2013, 05:27:47 PM »

Thanks

Tre'
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Ed Schilling
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« Reply #152 on: October 11, 2013, 05:44:34 PM »

I may still have that issue of SB. I built diaphragms from scratch to go in our magnet structures. They did work but buying them from ESS for 23 dollars and just sliding them in was much, much better...it made a "real" Heil.
Ed
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Tre
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« Reply #153 on: October 11, 2013, 06:20:06 PM »

Ed,

Can you get diaphragms for $23?

Tre'
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Ed Schilling
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« Reply #154 on: October 11, 2013, 06:47:54 PM »

Tre', LOL, that was in the '70s. I still have an invoice I think. It was a fortune to us back then.
Ed
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Tre
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« Reply #155 on: October 18, 2013, 03:35:47 PM »

I did some research and Steve is right. These things have to be dipole.

Every other vertical wire run moves in the opposite direction than the one beside it.

The front pleats are squeezing together while the back facing pleats are spreading apart and then that's reversed to complete one cycle.

It amazes me that these things can be so efficient considering that each wire run's motion is dependent on the electromagnetic field produced by that one wire hanging in a permanent magnetic field.

That must be one strong permanent magnetic field.

Sorry for being so hard headed about this.

This leaves the fact that the Great Heil has two magnetic structures with the most magnetic strength at the left and right extremes getting weaker as it approaches the center, has to be about high frequency dispersion. The patent states that above 8kHz the line source, that sit in the middle-in front of the pleats-in front of the pole pieces, gets thinner as the frequency goes up. Meaning that the dispersion gets wider as the frequency gets higher. Just the opposite of other type drivers.

" For the reproduction of low and medium frequencies these mass loadings have no effect, because the total air mass moved, which is about a quarter wave length air, is big compared with the loading effect. But at frequencies from about 8,000 Hz upwards, where the quarter wave length becomes comparable to the above mentioned air equivalents the mass loading reduces the diaphragm amplitudes on the edge of the diaphragm and forces the diaphragm activity more and more to the center as the frequency goes up. The sound emitted does not become directional, but spreads even at the highest audible frequencies very well over the front and back side of the speaker.

Another effect of the tapered pole pieces needs mentioning. The air moves not perpendicular to the diaphragm but it tends to cross the air gaps between the tapered pole pieces in the shortest possible distance. This is a straight path inclined towards the center of the diaphragm by half of the angle of each pole piece. This is in the illustrated speaker half of 45, that is 22%. That focusing effect further reduces the width of the sound source for the high audio frequencies and moves the sound focus out in front of the pole pieces.

Thus, the speaker has a frequency independent radiation pattern and cannot be acoustically localized very readily, even though it is practically a point source"

Tre'
« Last Edit: October 18, 2013, 03:37:24 PM by Tre » Logged
Ed Schilling
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« Reply #156 on: October 18, 2013, 04:23:57 PM »

Tre', jumpin" Jesus on a pogo stick! Thanks Tre'. A plausible explanation.

Every other vertical wire run moves in the opposite direction than the one beside it.
The front pleats are squeezing together while the back facing pleats are spreading apart and then that's reversed to complete one cycle.


I'm not convinced just yet. Was that statement in the patents? Thanks for the continuing discussion!
Ed

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Tre
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« Reply #157 on: October 18, 2013, 06:07:45 PM »

"Was that statement in the patents?"

No, but take a look at this,

http://hyperphysics.phy-astr.gsu.edu/hbase/audio/spk.html#c1

Steve is right. One wire with current running through it, part of that wire has the current running from top to bottom, part of that same wire has the current running from bottom to top.

The two parts of that one wire will, at any moment in time, move in opposite directions if both are suspended in the same permanent magnetic field.

Edit, I had the wrong link, it's fixed now.

Tre'
« Last Edit: October 18, 2013, 06:48:43 PM by Tre » Logged
Tre
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« Reply #158 on: October 18, 2013, 07:03:49 PM »

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Ed Schilling
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« Reply #159 on: October 18, 2013, 09:33:08 PM »

Tre', have you looked at the actual conductive path in a Heil diaphragm with relation to the folds? I've made them from scratch. Was a long time ago.
Ed
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Tre
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« Reply #160 on: October 19, 2013, 10:14:12 AM »

No I haven't but I assume the "wire" runs up the left side of the left most front facing pleat then crosses over at the top and runs down the right side of that same pleat, which is one side of the first rear facing pleat, then crosses over at the bottom to run up the left side of the next front facing pleat, which is the other side of the first rear facing pleat, etc...........all the way until it gets to the last side of the right most pleat.

Tre'
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Ed Schilling
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« Reply #161 on: October 19, 2013, 10:46:07 AM »

Tre', you need to find a real picture or a drawing of the pattern. I don't think your description is accurate. I'm not sure and I do think I still have the article showing how to make them but I'll look around. I think that happens to be one of the few issues I am missing! It seems like I loaned to someone in the 80's.

The pattern is not they way you'd think and was extremely difficult to cut out. Which is why we just started buying them from ESS. The factory ones use etched pattern on Kapton or Mylar and maybe some other materials have been used.

I do not think it is possible for the back pleats to squeeze while the fronts open. The diaphragm is folded just like as if you started at the edge of a piece of paper and folded it in say 1/2" folds until it was completely folded. Try it and then I think you'll see the front and backs squeeze and open at the same time. If they did not the thing would have to "bow" in order to have fronts open and backs closed. It does not bow.
They supposedly open and close and if that is the case the wave is the same front to back.

An accurate drawing or pic of the diaphragm should make it clear.
Ed
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Ed Schilling
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« Reply #162 on: October 19, 2013, 11:52:53 AM »

I still don't understand how air gets "sucked in" on the opposite side as the thing compresses. But I did find this........... maybe I'm slowly being convinced....at least until i actually measure the damn things one day!

The unique design feature of the OSKAR A.V.T. which distinguishes it from all other speakers is an extremely lightweight diaphragm, folded into a number of accordeon-like pleats to which aluminium foil strips are bonded. The Diaphragm is mounted in an intense magnetic field and a music signal is applied to the aluminum strips.
This causes the pleats to alternately expand and contract in a bellows-like manner in conformance with the music signal forcing air under pressure out of the pleats and sucking the air in on the other side, the airmovement is 5 times bigger than the movement of the membrane, therefore also the velocity must be 5 time bigger.The total moving mass is approx. 1 gram, we have therefore an almost perfect transducer system. This principle can be demonstrated very simply by taking a sheet of DIN A 4 paper with a surface of 616 cm2, folding it in the center lengthwise and bending the long edges together to form an opening of 5 cm on the one side. We imagine, that the upper and lower part of the structure is closed and move each side 2.5 cm together. With a frontal surface of 140 cm2, we have now moved 770 ccm of air, compared with the 350 ccm of air moved by a flat diaphragm. Our transformation is now 1:2.2, by making the triangle (top view) a square form, we doubled the transformation to 1:4.4 The selected transformation ratio with the Oskar A.V.T. is 1:5.3.
Unlike conventional speakers, whos diaphragms move air only in a direct proportion to their own movement with the inherent inertia. The A.V.T. multiplies (transforms) the Air Velocity by a factor of 5.3 (with a total mass of less than 1 gramm) and is, therefore, appropriately called an “AIR VELOCITY TRANSFORMER.”
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Tre
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« Reply #163 on: October 19, 2013, 12:13:37 PM »

From the patent,

FlG. 4a illustrates schematically an arrangement in which metal foils are arranged to opposite sides of the plastic corrugated sheet of the diaphragm means, and in which the metal foils on opposite sides of the sheet are connected in parallel to each other;

FIG. 4b is a schematic view :similar to that shown in FIG. 4a in which the metal foils to opposite sides of the sheet are in series connected



Series or parallel the current flows the same way and direction causing each half of each pleat to move either in, toward the center of that pleat, or out, away from the center of that pleat.

When the left wall of a front facing pleat moves to the right toward the center, the right wall of that same pleat moves to the left towards the center causing that pleat to close. The right wall of that front facing pleat is the left wall (looking from the front) of a back facing pleat.

The next "wire" to the right is the left side of the next front facing pleat and the right (looking from the front) of the back facing pleat. Just like the first wire I've described here it will be moving to the right. That will cause the back facing pleat to open up.

Like you said, fold up a small piece of paper. Look at just the first 3 pleats starting at the left.

Two of them facing the front and the one in the middle facing the back.

When the left side of each of the two forward facing pleat move to the right and at the same time the right side of each of the two forward facing pleats move to the left, the two front pleats are closing and at the same time the one rear facing pleat is opening up.

Tre'
« Last Edit: October 19, 2013, 12:23:36 PM by Tre » Logged
Tre
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« Reply #164 on: October 19, 2013, 12:21:55 PM »




When pleat wall 1 moves to the right pleat wall 2 is moving to the left then pleat #1, as marked on the picture, is closing.

Pleat wall 3 is, at that same time, moving to the right and pleat wall 4 is, at that same time, moving to the left then pleat #3, as marked on the picture, is closing.

Pleat wall 2 is moving to the left and pleat wall 3 is moving to the right, opening pleat #2 as marked on the picture.

Pleat #1, as marked in red, and pleat #3 face the front and are closing while pleat #2 that faces the rear is opening.

Tre'
« Last Edit: October 19, 2013, 12:26:39 PM by Tre » Logged
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