The Transducers' Voice Coil

[smowry]

No, I don't want to buy anything, I'm just interested in the motor design.
I only buy speakers from the PA corner > BMS, RCF, B&C, 18sound, Sica, Beyma and FaitalPRO.

You can only purchase that transducer from Parts Express.

Brother Vance gave it a through review but Dayton sent him a selected unit.

Test Bench: The E150HE-44 5.5” Full-Range Subwoofer from the Dayton Audio Epique Line

This Test Bench explication focuses on the Dayton Audio Epique MMAG E150HE-44 "full-range subwoofer," in itself an interesting concept. Like its larger E180HE-44 brother in the Epique line, the E150HE-44 is based on the patented Multiple Magnet Air Gap (MMAG) technology invented by Enrique...

audioxpress.com

The motor looks like Enrique Stiles design but the Dayton uses Neo top mannets.

https://patentimages.storage.googleapis.com/44/ee/ec/7c63eed8308981/US7065225.pdf (Note that the Patent has expired.

The motor topology is XBL^2 with the added top magnet between the gap plates. Both motors implement 2 gaps. That was considered another 20 year protected invention.

https://patentimages.storage.googleapis.com/42/62/ac/427d0643b17eca/US7039213.pdf

 

[KSTR]

Unfortunately, unless someone can show me otherwise, I claim the tapered wire concept is heresy!

The force generated by the coil is force-factor times current, f=i*BL. This also true for any small segment of the voice coil and all the forces at the various positions add up.
The current is created along the total static VC impedance and thus is constant in any segment.

If we have a section with lower B than nominal, how can we compensate resulting force for that, say, when B has halved? By increasing L for that segment to twice its value. f=i*B/2*L*2. L can be increased by narrower pitch of the wire, half as narrow.

Ideally, we also don't want to have void spaces in the winding by actually using standard wire and change packing factor, like Purifi did in their VariablePitch 2-layer VC.

Therefore, the optimal solution would be to use rectangular wire with constant width but variable height. In regions where BL is lower the height is reduced to compensate for that, as outline above.

 

[smowry]

The force generated by the coil is force-factor times current, f=i*BL. This also true for any small segment of the voice coil and all the forces at the various positions add up.
The current is created along the total static VC impedance and thus is constant in any segment.

If we have a section with lower B than nominal, how can we compensate resulting force for that, say, when B has halved? By increasing L for that segment to twice its value. f=i*B/2*L*2. L can be increased by narrower pitch of the wire, half as narrow.

Ideally, we also don't want to have void spaces in the winding by actually using standard wire and change packing factor, like Purifi did in their VariablePitch 2-layer VC.

Therefore, the optimal solution would be to use rectangular wire with constant width but variable height. In regions where BL is lower the height is reduced to compensate for that, as outline above.

Disagree: The amp sees the entire coil with length, L, regardless of position. However, the coil only sees the B in the gap, B(x). So the nonlinear parameter is really B(x)L, but
B(x)L = BL(x). It's just notation. The effective L does not change with position only B changes, B(x).

We did this with the dual voice coil example.

Pararall: L = L with (2S)

Series: L = 2L with (S)

Volume for dual coil = 2LS

Spl does not change between L and 2L: 1.0 W @ 1 m Then force/power does not change from L to 2L

Beta does not change and Beta(x) and Beta relate to Volume and we don't care about L. Additionally we don't care about the N, the number of turns. We care about the volume of conductor. A true ribbon transducer has ZERO turns, N = 0!

We don't care about L; we care about Volume. You cannot assume the L changes with position. You need to commutate the voice coil to do that!

Thilo's LMS coil changes volume vs. position, V(x) by changing S(x), the coil OD must vary with position, while the ID remains unchanged, volume(x).

Here comes the kicker.

Assume 2 dimensions. Looking at a sheet of paper.

i = V/R (Ohm's Law)
R = (resistivity)L/S
L = N(pi)Diameter
BLi = B[N(pi)Diameter]V(S)/[N(pi)Diameter(resistivity)]
BLi = BV(S)/resistivity
BLi = [BV](S(x)/resistivity
BLi(x) = B(x)(V)S(x)/resistivity

Please do not claim that my proof is invalid for rectangular wire. The theory is the same but adding another dimension, 3D makes the calculation much more complex.
We change the cross-section by changing the coil OD(x) to offset the change in B(x).

If the only N that counts is the segment in the gap, why do we need to commutate the voice coil? You claim to turn on or off coil segment by moving the coil trough the gap.

Intuitively there is an existing example, Thilo's LMS coil. Where both N and Volume are increased as the |x| is increased. It has been shown that it is volume that changes the force vs. position. You claim that that the volume of conductor in the gap can be constant, with coil OD and ID constant, then force varies with N changing with position, N(x). I claim that is heresy.

@jackocleebrown

Hi Jack,


I could use your help with resolving a voice coil issue. I am confronted with a misunderstanding by several members. If you are too busy, it's okay but in a case like this it may take "Superman" to save the day.


Thanking you in advance,


Steve

 

[mwmkravchenko]

You can only purchase that transducer from Parts Express.

Brother Vance gave it a through review but Dayton sent him a selected unit.

Test Bench: The E150HE-44 5.5” Full-Range Subwoofer from the Dayton Audio Epique Line

This Test Bench explication focuses on the Dayton Audio Epique MMAG E150HE-44 "full-range subwoofer," in itself an interesting concept. Like its larger E180HE-44 brother in the Epique line, the E150HE-44 is based on the patented Multiple Magnet Air Gap (MMAG) technology invented by Enrique...

audioxpress.com

The motor looks like Enrique Stiles design but the Dayton uses Neo top mannets.

https://patentimages.storage.googleapis.com/44/ee/ec/7c63eed8308981/US7065225.pdf (Note that the Patent has expired.

The motor topology is XBL^2 with the added top magnet between the gap plates. Both motors implement 2 gaps. That was considered another 20 year protected invention.

https://patentimages.storage.googleapis.com/42/62/ac/427d0643b17eca/US7039213.pdf

I've modeled that motor. It is a total failure. The top gap is 40% weaker than the bottom gap. In fact I have designed replacement drivers for an OEM for that exact reason.

 

[mwmkravchenko]

Unfortunately, unless someone can show me otherwise, I claim the tapered wire concept is heresy! If I have not made that clear by now, something is wrong. Remember, the concept is not related to people, rather it is related to transducers.

100% agreement Steve. No net gain in motor force. Incredibly difficult to wind. And debatable if you gain anything. I drew it out for clarity, and to describe it well. I think I stated that the greater turns density increased the Re, so no net motor force gain. Maybe a flattening of the B curve. I might be able to model that as a 3 part series voice coil. BUt I think that's beating a dead horse.

Mark

P.S> The idea that you could 3D print this successfully is Not part of what can be accomplished via 3D printing at this time. It's not only multi-materials, it is on scales that I have never seen a 3D print. The voicecoil bobbin is maybe 0.125mm? The starts and stops needed to print and then sinter a wire and an insulator? Sorry. Science Friction. (OnPurpsoe, rubs Science the wrong way)

 

[mwmkravchenko]

How do you rate the dual gap MMAG motor design of the Epique series from Dayton Audio?
View attachment 503826

Dayton Audio - E150HE-44 5-1/2" DVC MMAG Extended Range Subwoofer 4 Ohms per Coil

E150HE-44 5-1/2" DVC MMAG Extended Range Subwoofer 4 Ohms per Coil

www.daytonaudio.com

Test Bench: The E150HE-44 5.5” Full-Range Subwoofer from the Dayton Audio Epique Line

This Test Bench explication focuses on the Dayton Audio Epique MMAG E150HE-44 "full-range subwoofer," in itself an interesting concept. Like its larger E180HE-44 brother in the Epique line, the E150HE-44 is based on the patented Multiple Magnet Air Gap (MMAG) technology invented by Enrique...

audioxpress.com

That is simulated with a complete ring magnet on the top. About 15% more flux than you can get with discs. It simply doesn't work.

In case this is not understood. This is an exact model of the Epic driver.

What I designed as a replacement was a true underhung.

The one that does work, and is a true underhung is in the Evolution Acoustics Model One:

MODEL ONE

MODEL ONE Natural. Transparent. Holographic. The foundational philosophy of Evolution Acoustics and basis of our flagship SYSTEM loudspeakers carries throughout each and every product design and th…

www.evolutionacoustics.com

I did the transducer design only. Kevin knows what he's doing for crossover work.

Mark

 

[smowry]

@KSTR Last try!

We have a Cu voice coil with constant OD and constant ID and constant wind height and N turns. Where L = N(pi)D. So now you claim that you can increase the transducer efficiency by increasing N but keeping the same OD and ID and wind height. The theory is the same for global or a local section. You must change volume of conductor to change Beta. This means that the OD must increase if ID and wind height are held constant. If OD and ID and wind height are all constant, changing N will not change Beta. Inductance, Le, and Re will change but Beta will not. You cannot change Beta by changing N but keeping the volume constant either globally or locally. It's analogous to the dual voice coil. When you increase N you increase Re.



Below is a plot of Bl(x) and Beta(x) for the same motor assembly. If you change Bl (Tm) you also change Beta (N^2/W). Note Power = Vi (W).



Ohm's Law, V = (Re)i.
Re = (resistivity) [N(pi)diameter] / S
S = wire cross-section
V = (resistivity) [N(pi)diameter] i / S
i = V S / (resistivity) [N(pi)diameter]

When you increase N you decrease i

Purifi's voice coil has varying volume! The OD changes locally with position. Is the Purifi your proof of claim by example?

Purifi's voice coil is proof by example for my claim. OD and thus volume changes with position. Remember the voice coil is a flux integrator.

Here's Thilo's LMS Voice Coil. It is similar with varying OD and thus varying volume of conductor vs. position.

Here's your claim: "Therefore, the optimal solution would be to use rectangular wire with constant width but variable height. In regions where BL is lower the height is reduced to compensate for that, as outline above."

Constant width means constant OD. Then you increase N locally. I claim that your claim is heresy! I challenge you to show the proof of your claim.

 

[KSTR]

@smowry , I think we have a misunderstanding here.

Assume the normal way of doing it, say like Purifi example, and we do agree that this works to linearize force factor vs VC position.
However, we now have some unused volume in the gap and my thinking is that one can make use of that volume by a paralleled VC in those sections, so to say. In the end, increase local conductivity. Neither local nor global force factor have changed by this, true, but we lowered total Re, that was my point.

Think of the dual VC driver, with one winding not connected (the unused volume), and driven by a certain current establishing a force. When we parallel the 2nd coil and drive the whole thing with same current we get the same force, obviously. But we have halved the total Re and thus have doubled total (BL)²/Re. Both efficiency and sensitivity will increase accordingly.

@mwmkravchenko , I do agree that this sounds like science fiction. But 3D-printing stuff as we do already today also was total science fiction 30 years ago.
One could also create the tapered wire by a dynamic wire-drawing technique with an real-time adjustable die. Yes, again very high precision will be needed for the whole process of making the wire and winding it on the former.

At the and of the day, the optimization might not be very relevant but for high power designs improvements in the 10% range could be worthwhile.

 

[smowry]

@smowry , I think we have a misunderstanding here.

Assume the normal way of doing it, say like Purifi example, and we do agree that this works to linearize force factor vs VC position.
However, we now have some unused volume in the gap and my thinking is that one can make use of that volume by a paralleled VC in those sections, so to say. In the end, increase local conductivity. Neither local nor global force factor have changed by this, true, but we lowered total Re, that was my point.

Think of the dual VC driver, with one winding not connected (the unused volume), and driven by a certain current establishing a force. When we parallel the 2nd coil and drive the whole thing with same current we get the same force, obviously. But we have halved the total Re and thus have doubled total (BL)²/Re. Both efficiency and sensitivity will increase accordingly.

@mwmkravchenko , I do agree that this sounds like science fiction. But 3D-printing stuff as we do already today also was total science fiction 30 years ago.
One could also create the tapered wire by a dynamic wire-drawing technique with an real-time adjustable die. Yes, again very high precision will be needed for the whole process of making the wire and winding it on the former.

At the and of the day, the optimization might not be very relevant but for high power designs improvements in the 10% range could be worthwhile.

@KSTR

You sure do have a misunderstanding.

So you are proposing a dual voice coil but rather than duplicating each other, the coils complement each other. Furthermore, you propose to connect the coils in parallel.

Parallel: Then what is L, Jose?

L1 || L2 is it L1L2/(L1 + L2)?

Series:

L1 + L2 L is the sum.

However, and as you know, series vs. parallel really makes no difference. We don't care about L; we care about volume. Furthermore, BL alone is a meaningless parameter. Why do you refuse to consider Beta, the true figure of merit?

The result of your proposal is a dual voice coil with constant ID and OD with varying N(x); therefore constant volume. That will do nothing to improve linearity. All that will be accomplished is to render the coil impossible to manufacture with added potential failure modes. I presented a complete derivation of this case; however, you refuse to accept my derivation and instead of presenting your derivation you chose to be argumentative. You have made no corrections, additions, or alternative derivations. I maintain that your proposal is heresy.

Beta(x) = [BL(x)^2]/Re N^2/W
Then Beta(x) = (B(x)^2)L(x)S(x)/rho
Then Beta(x) = [B(x)^2]Volume of conductor/rho Constant voice coil OD and ID
LMS: Beta(x) = [B(x)^2]Volume of conductor(x)/rho

Do you ever use mathematics to validate your proposals?

The only way I can see to make your proposal work is to use copper, copper clad aluminum, and/or aluminum wire, where copper and/or CCA wire would be located such that the reduced resistivity could increase Beta locally, rho(x).

Beta(x) = [B(x)^2]Volume of conductor/rho(x)

Don't bother tapering the wire, it is ineffective.

This proposal would result in reduced voice coil manufacturability but not an impossibility. And I presented a simple derivation, just change resistivity vs. position. Bingo!

I am very disappointed in you!

See the concept sketch below, Jose.

Just wait until Dr. Jack gets here!

 

[KSTR]

Figure to better explain things, cross-section of packing of the VC with variable pitch

From left to right the winding topology evolves:

First, we have the standard way as shown by Purifi and LMS examples.
Second, we add a parallel winding w1' to w1 in the unused space to decrease total Re without affecting the local force factor.
Third, we combine that two paralleled windings into one with double the cross section, not affecting geometry otherwise.
Fourth, we geometrically rearrange the series'd windings w2 and w3 so that the layering now is vertical instead of horizontal.

End result is a rectangular wire with constant width but tapered height for maximum packing, and this new 1-layer VC has a lower total Re than the original arrangement.

I find it always helpful to regard Re as a parasitic external resistance to a super-conducting winding which therefore could have negligible cross-section area. Then it becomes readily apparent that the final arrangement is implementing the variable vertical winding pitch very literally.

 

[KSTR]

I find it always helpful to regard Re as a parasitic external resistance to a super-conducting winding

This is the really important aspect of it. The local conductivity of the wire does not matter, nor does its distribution along the total wire length. Only total Re counts, the current and the number of turns per unit height (which is the variable pitch, after all).

 

[smowry]

Figure to better explain things, cross-section of packing of the VC with variable pitch
View attachment 504042
From left to right the winding topology evolves:

First, we have the standard way as shown by Purifi and LMS examples.
Second, we add a parallel winding w1' to w1 in the unused space to decrease total Re without affecting the local force factor.
Third, we combine that two paralleled windings into one with double the cross section, not affecting geometry otherwise.
Fourth, we geometrically rearrange the series'd windings w2 and w3 so that the layering now is vertical instead of horizontal.

End result is a rectangular wire with constant width but tapered height for maximum packing, and this new 1-layer VC has a lower total Re than the original arrangement.

I find it always helpful to regard Re as a parasitic external resistance to a super-conducting winding which therefore could have negligible cross-section area. Then it becomes readily apparent that the final arrangement is implementing the variable vertical winding pitch very literally.

HERESY!

Only the first sketch (if one can even call that a concept sketch) will change volume with position, volume(x). The other three appear to be constant volume and constant resistivity,

Then: Beta(x) = [B(x)^2]Volume of conductor/rho Constant voice coil OD and ID and wind height, looks ineffective.

Here's the gentlemen that showed me the Beta derivation back in 1994. At that time he was the Electromagnetic scientist at BOSE. He also trained me in the use of Vector Fields Opera. https://www.linkedin.com/in/ric-carreras-7708821/

If he were here, he would be infuriated by your heresy.

 

[smowry]

Use superposition.

Resistivity does matter.

Re = resistivity(L)/S Just use any wire, right?

Beta(x) = [B(x)^2]Volume of conductor/rho(x)

 

[smowry]

Three coil Superposition:

BetaAl(x) = [B(x)^2]Volume of Al/rhoAl(x)

BetaCCA(x) = [B(x)^2]Volume of CCA/rhoCCA(x)

BetaCu(x) = [B(x)^2]Volume of Cu/rhoCu(x)

Beta(x) = BetaAl(x) + BetaCCA(x) + BetaCu(x)

 

[KSTR]

OK, let's agree to disagree and leave it at that, for the moment.

One final note you may want to think about:
You can make the same VC with copper or aluminum wire as the only difference, then add the delta of resistance with an external resistor to the copper VC and voila, same efficiency and sensitivity, same total dissipated power, same everything ==> conductivity distribution along the total VC conductor length does not matter, QED.

 

[smowry]

OK, let's agree to disagree and leave it at that, for the moment.

One final note you may want to think about:
You can make the same VC with copper or aluminum wire as the only difference, then add the delta of resistance with an external resistor to the copper VC and voila, same efficiency and sensitivity, same total dissipated power, same everything ==> conductivity distribution along the total VC conductor length does not matter, QED.

More HERESY!

Show me the derivation of your heretic claim of "same everything".

Here's my claim.

Beta(x) = [B(x)^2]Volume of conductor/rho(x)

Have you ever actually designed a voice coil?

 

[KSTR]

Variable Pitch VC essentially means changing the number of turns per unit height along the extension of the coil, aka a varying turns density. This in turn changes force per unit height proportionally to turns density, resulting in a varying force density which can counteract a varying flux density. So far so good, we have working examples of this as noted previously.
F = i * B * L, globally as well as locally per unit height.

Summarized, we have some turns density profile to linearize total force factor BL(x), and we also have an overall turns density scale factor which sets the impedance level in the usual way.

As long as the correct varying turns density profile is maintained to linearize total BL(x), conductivity (total and local) and all that comes with it does not matter for the effect, these variables do not appear in above relationship. One could use hair-thin superconducting wire, for the complete coil or only parts of it, it doesn't matter. What counts is the geometrical arrangement of the wire centroids which sets up the turns density.

This allows to optimize efficiency by filling all available volume of the VC in the way I've show conceptually in post #50, with tapered rectangular wire, as per my initial claim. It also gives the best possible (lowest) Qes.

 

[smowry]

Jack never showed. I hope everything is okay. Does anybody know anything? Jack is such a nice guy.

 

[mwmkravchenko]

Jack never showed. I hope everything is okay. Does anybody know anything? Jack is such a nice guy.

We fools rushed in where a wise man dare not tread.