A technical discussion of the Borresen ironless woofer.

[smowry]

René,

Thanks for stopping by. When I was practicing, I had the same concerns that you indicated you have and I avoided public forums. Now I am retired in Thailand and several of my previous clients (the important ones anyway) have passed away. So I no longer have those concerns and now I feel compelled to debunk certain products and companies that I feel are not up to reasonable loudspeaker industry standards. Typically as a minimum they misrepresent their products and make false claims. I feel strongly that Borresen et al. fits this description and then some.

Then I will say it is nice to meet you and if Amir recognizes you, then you are top notch. As I posted before you arrived, the simulations that I am presenting are at least 15 to 20 years old. I used to be a real R&D Transducer Engineer; however, I have been put out to pasture in Phuket and I love it!

Then having said all that, I am gunning in a technical sense for General Danny Richie and Elizabeth Michael Borresen. I want to debunk as much of their misinformation as I can similar to what Amir does with electronics, power cords, and interconnects etc.

 

[Snickers-is]

I think it is important to show integrity towards the end users when you work in the industry as well. There are just too many hoax-companies out there, and I would not consider working with them unless I am able to offer some valuable input. If they just want to slap my name on a product, I would rather avoid them. The companies I want to work with are those who want to demonstrate to the world that they have integrity, and that they push to improve actual sound quality and musical experience for the end users. I really do not think I can offer a service to one company where I have integrity, and the next day I offer a service to a different company where I have to throw any trace of integrity away.

 

[smowry]

A few years ago, they put the driver parts up for display on a show. It gave me the oportunity to see exactly how it all is built, and yes, it is as simple as previously revealed here. It gave me the oportunity to run a FEM model to see the Bl(x), and this is what I got:

View attachment 442871

As anyone who has been dealing with FEM simulations would know, there are very few variables involved once you have no paramagnets and no asymmetry. So it is safe to assume this is pretty accurate. What is unlikely to be accurate is the force factor itself, but any change in windings and magnet class would only rise or lower the same curve a certain amount.

Something else we know about the driver is based on a claim made several times by the company. The impedance peak at Fs is extremely low. It is claimed to be due to the low inductance, which is simply not true. The inductive and capacitive components forming this peak are the mass and the suspension of the driver. The electrical inductande do not play a role in this.

There are a few ways to get this peak low. One is to introduce mechanical loss leading to low Qms. Another one is that you could in theory make a driver that has low mass and extremely loose suspension, but it would not be able to play any bass in a real world enclosure. Changing Le would not affect this peak unless it is extremely high to begin with. Since we know these woofers are quite traditional in therms of T/S we can say for sure that they are very lossy. It is actually quite impressive to get that amount of loss without an aluminium voice coil former.

Regarding patents @smowry , I am not sure there is any reason to be annoyed. There are only two possibilities here. One is that the patent is impossible to defend in court as it is easy to prove that it is prior art. The other one is that the detail it is approved based on is so tiny, it does not give any protection for the function of the product, and probably is still impossible to defend in court. We have the same situation with D Wiggins in 2003 or something where he re-patented an old Babb-patent from 1976 (the split gap). It was later revealed that it was approved based on the following:

1: A sentence in Babbco's patent stated, after the description of using two gaps and describing the possibility to add even more gaps, something like this: "Adding even more gaps would not have any practical advantage". Wiggins' attourney was able to convince the clerk that this sentence also included 2 gaps. While anyone with any understanding of the topic knows that using two gaps would add some advantage, while adding a third would not, the clerk obviously did not know this. This would off course make this patent impossible to defend in court.

2: A tiny groove in the pole piece between the two gaps were not added in Babb's patent in 1976. While it is an absolutely obvious thing to do in a world of T-shaped pole pieces, they were able to convince the clerk that this was a new invention. This too would probably have been pretty hard to get anywhere with in court.

Firstly, great post and happy to see other people are watching Borresen.

Now with respect to the apparent damping that you describe and for example, if I mount a woofer in a pipe and I stuff the pipe with acoustic resistive materials and leave the pipe open, I can control the natural frequency impedance peak by the density of the stuffing. This will manifest itself as you indicated as a reduction in Qms (increased mechanical losses). Did he just heavily stuff the enclosure?

Then if BETA = (Bl)^2/Re is very low, the impedance peak will be small but assuming an Re ~ 4 ohms and Bl(Max) ~ 10, then Beta ~ 25 (N^2/W) which would be good for that size transducer and would not indicate a smaller impedance peak to me. Planar tweeters tend to have very little natural frequency peaks because BETA tends to be very low.

We need to figure this out if possible.

Then based on 0.82Bl(max) = Bl(Xmax) ~ 5.2mm. For an alleged high performance woofer, that is less than a fair result.

The USPTO is a disgrace and I use the Elizabeth Holmes as an example.

I know Dan and he's okay. He is definitely not a Borresen. Patrick and Enrique are okay too. Borresen and Richie are not okay and should be censured and debunked whenever possible.

 

[René - Acculution.com]

René,

Thanks for stopping by. When I was practicing, I had the same concerns that you indicated you have and I avoided public forums. Now I am retired in Thailand and several of my previous clients (the important ones anyway) have passed away. So I no longer have those concerns and now I feel compelled to debunk certain products and companies that I feel are not up to reasonable loudspeaker industry standards. Typically as a minimum they misrepresent their products and make false claims. I feel strongly that Borresen et al. fits this description and then some.

Then I will say it is nice to meet you and if Amir recognizes you, then you are top notch. As I posted before you arrived, the simulations that I am presenting are at least 15 to 20 years old. I used to be a real R&D Transducer Engineer; however, I have been put out to pasture in Phuket and I love it!

Then having said all that, I am gunning in a technical sense for General Danny Richie and Elizabeth Michael Borresen. I want to debunk as much of their misinformation as I can similar to what Amir does with electronics, power cords, and interconnects etc.

Nice to meet you too. It is always good to debunk misinformation, and I try to do that myself also. I am not sure if it changes much, but at least you can say that you tried ;-)

 

[Snickers-is]

Firstly, great post and happy to see other people are watching Borresen.

Now with respect to the apparent damping that you describe and for example, if I mount a woofer in a pipe and I stuff the pipe with acoustic resistive materials and leave the pipe open, I can control the natural frequency impedance peak by the density of the stuffing. This will manifest itself as you indicated as a reduction in Qms (increased mechanical losses). Did he just heavily stuff the enclosure.

Then if BETA = (Bl)^2/Re is very low, the impedance peak will be small but assuming an Re ~ 4 ohms and Bl(Max) ~ 10, then Beta ~ 25 (N^2/W) which would be good for that size transducer and would not indicate a smaller impedance peak to me. Planar tweeters tend to have very little natural frequency peaks because BETA tends to be very low.

We need to figure this out if possible.

Then based on 0.82Bl(max) = Bl(Xmax) ~ 5.2mm. For an alleged high performance woofer, that is less than a fair result.

The USPTO is a disgrace and I use the Elizabeth Holmes as an example.

I know Dan and he's okay. He is definitely not a Borresen. Patrick and Enrique are okay too. Borresen and Richie are not okay and should be censured and debunked whenever possible.

The measurements were of the driver itself, and not the driver mounted in this speaker. And stuffing does not play a significant role in this anyway.

I suspect there might be some other stuff involved here. They have shown some measurements here:

Børresen 02

6moons.com

The DATS for the standmount model shows this:

And for the larger floorstander 03, it shows this:

I think the latter is a 2,5 way, while the standmount one is a two way. It looks like it might not be the same driver, but I am not sure. Michael showed me the DATS screenshot of the driver itself on his phone, I think it might have been 5+ years ago. It showed the free air resonance to have a unusually low peak, indicating Qms lower than 1. That would be a very audible amount of mechanical loss. The impedance curves for the speakers themselves are probably with some kind of filter correction, probably to make the secondary .5-way coil work without providing way too much boost in the low mid. But it is kind of entertaining to read that they claim the phase to be linear based on the electrical phase of a lossy system. This is a bass reflex design after all, and we have seen some acoustic measurements where the word "linear" is not the first that comes to mind.

 

[smowry]

Snickers-in,


What grade of NdFeB BH curve did you use in your model and do you know the DC resistance of the voice coil?

I have DATS and those are impedance sweeps but what we need to see "measure free air parameters" option. However, using Dr. Small's model, some of the small signal parameters can be extrapolated including Q's and fs. I have never seen impedance sweeps of a single driver like that or is it a system. If you had just shown me those sweeps without any comment, I would have said that there was crap in the gap that was causing those strange curves with what appear to include multiple resonances. Crap in the gap can result in wild impedance sweeps. Is it possible that that was the case and he wanted to throw you off the cliff? Frankly, there is no special or mystical stuff in moving coil transducers. You know just about everything if not everything. And if there is surely Borresen will not find it before Dan, Patrick or Enrique. Borresen is not an innovator. He is an imitator.

If the motor had demaged, the natural frequency impedance peak would be low regardless of your FEM model. I don't believe Qms < 1 is possible in a properly functioning woofer. That just seems impossible unless something is wrong.

Anyway, it was a common opinion when I was practicing that mechanical losses should be minimized. If someone proposed a transducer concept with a Qms of less than 1 at BOSE, that person would have been belittled and mocked to such an extent he would have been forced to quit. A Qms of less than one is a controversial implementation the indicates something is wrong and not that something secret is right.

 

[Snickers-is]

Snickers-in,


What grade of NdFeB BH curve did you use in your model and do you know the DC resistance of the voice coil?

I have DATS and those are impedance sweeps but what we need to see "measure free air parameters" option. However, using Dr. Small's model, some of the small signal parameters can be extrapolated including Q's and fs. I have never seen impedance sweeps of a single driver like that or is it a system. If you had just shown me those sweeps without any comment, I would have said that there was crap in the gap that was causing those strange curves with what appear to include multiple resonances. Crap in the gap can result in wild impedance sweeps. Is it possible that that was the case and he wanted to throw you off the cliff? Frankly, there is no special or mystical stuff in moving coil transducers. You know just about everything if not everything. And if there is surely Borresen will not find it before Dan, Patrick or Enrique. Borresen is not an innovator. He is an imitator.

I believe you find answers to all of your questions in my posts.

 

[smowry]

Can anyone else comment on the impedance sweeps?

 

[smowry]

I believe you find answers to all of your questions in my posts.

Can you give me a hint? I reviewed you posts again and searched (ctrl +f) BH and resistance and I still cannot find the answers to either question.

Can I ask you to post the magnet BH curve? I used to export FEM magnet BH curve (text) files into VF OPERA. Is your FEM model at room temperature, typically 25C?

 

[AOR]

A few years ago, they put the driver parts up for display on a show. It gave me the oportunity to see exactly how it all is built, and yes, it is as simple as previously revealed here. It gave me the oportunity to run a FEM model to see the Bl(x), and this is what I got:

View attachment 442871

As anyone who has been dealing with FEM simulations would know, there are very few variables involved once you have no paramagnets and no asymmetry. So it is safe to assume this is pretty accurate. What is unlikely to be accurate is the force factor itself, but any change in windings and magnet class would only rise or lower the same curve a certain amount.

Something else we know about the driver is based on a claim made several times by the company. The impedance peak at Fs is extremely low. It is claimed to be due to the low inductance, which is simply not true. The inductive and capacitive components forming this peak are the mass and the suspension of the driver. The electrical inductande do not play a role in this.

There are a few ways to get this peak low. One is to introduce mechanical loss leading to low Qms. Another one is that you could in theory make a driver that has low mass and extremely loose suspension, but it would not be able to play any bass in a real world enclosure. Changing Le would not affect this peak unless it is extremely high to begin with. Since we know these woofers are quite traditional in therms of T/S we can say for sure that they are very lossy. It is actually quite impressive to get that amount of loss without an aluminium voice coil former.

Regarding patents @smowry , I am not sure there is any reason to be annoyed. There are only two possibilities here. One is that the patent is impossible to defend in court as it is easy to prove that it is prior art. The other one is that the detail it is approved based on is so tiny, it does not give any protection for the function of the product, and probably is still impossible to defend in court. We have the same situation with D Wiggins in 2003 or something where he re-patented an old Babb-patent from 1976 (the split gap). It was later revealed that it was approved based on the following:

1: A sentence in Babbco's patent stated, after the description of using two gaps and describing the possibility to add even more gaps, something like this: "Adding even more gaps would not have any practical advantage". Wiggins' attourney was able to convince the clerk that this sentence also included 2 gaps. While anyone with any understanding of the topic knows that using two gaps would add some advantage, while adding a third would not, the clerk obviously did not know this. This would off course make this patent impossible to defend in court.

2: A tiny groove in the pole piece between the two gaps were not added in Babb's patent in 1976. While it is an absolutely obvious thing to do in a world of T-shaped pole pieces, they were able to convince the clerk that this was a new invention. This too would probably have been pretty hard to get anywhere with in court.

My simulations show something reasonably similar.

I drew a Borresen-esque (or Mowry-esque) motor geometry. The VC diameter is 75mm, with a "gap" height of 10mm. I added rads on the "corners" of the "gap" because I felt like it. This motor is larger, in every dimension to the ones actually produced by Borresen, but hits a peak gap flux of around 1T, and has a decent amount of excursion.

B(x) looks like this:

If the length of the voice coil can be matched to the distance between the peaks, a relatively flat BL(x) should be possible.

Using a copper voice coil with the below parameters:

Gives a BL(x) of:

 

[smowry]

What does the impedance sweep look like if one forgets to magnetize a transducer within the manufacturing process? I believe that the natural frequency impedance peak would be very small but still at fs and Re would not be affected.

 

[smowry]

Now I have become confused. Your model geometry does not seem to match picture from the Borresen website nor the patent images.

Note that the picture seems to match the patent immage which was created from a 2D mechanical drawing. Your model shows what appear to be much taller magnets, which I would have expected but did not see before. So could you please confirm if your model is different from the picture from the Borresen website shown above. Otherwise the model look great, just different from the picture.

 

[AOR]

Now I have become confused. Your model geometry does not seem to match picture from the Borresen website nor the patent images.

View attachment 442926

View attachment 442933
Note that the picture seems to match the patent immage which was created from a 2D mechanical drawing. Your model shows what appear to be much taller magnets, which I would have expected but did not see before. So could you please confirm if your model is different from the picture from the Borresen website shown above. Otherwise the model look great, just different from the picture.

View attachment 442927

Yeah, I have much longer magnets. This was done a few years ago, not something I did recently. It's completely unoptimised, so reducing magnet height would be pragmatic thing to do, considering the middle section doesn't appear to doing much for the flux.

 

[smowry]

The irony is that what you modeled should be significantly more robust than what is in the website picture and mechanical drawing. Making the magnets tall will raise the operating point of the magnets and will change the magnetic fields within the magnet because the operating point relates directly the where the magnets are on their respective BH curve. If below is your |B| contour plot, the analysis would be linear and there is no BH curve. Constant values of B and H are assigned to the magnet.

This might be okay to illustrate the basis principal of the ironless motor; however, to effectively analyze an ironless motor assembly, nonlinear FEA with the appropriate BH curve must be utilized. Magnets in a motor assembly never have constant fields. The fields vary with position inside the magnet depending on the points on the BH curve. Twetety years ago FEM did nonlinear DC FEA and even came with an assortment of BH curves for commonly used magnets. The motor is a dynamic system and its more than just the DC flux in the gap and assuming nagnet height does not do anything. Nothing could be father from the truth! As I indicated within the first few posts, setting the operating point and magnet grade selection are critical. So this is simple. If the analysis is nonlinear, then a BH curve file is required and FEM will allow the user to load various BH curves. These are text files that can be opened and edited with notepad and they can be plotted with Matlab or Mathcad. Can you post a BH curve, either plotted or just the point within the text file? Every grade of NdFeB magnet has it own BH curve. My guess was N50 but it's just a guess. I have posted N48 below.

 

[AOR]

The irony is that what you modeled should be significantly more robust than what is in the website picture and mechanical drawing. Making the magnets tall will raise the operating point of the magnets and will change the magnetic fields within the magnet because the operating point relates directly the where the magnets are on their respective BH curve. If below is your |B| contour plot, the analysis would be linear and there is no BH curve. Constant values of B and H are assigned to the magnet.

View attachment 442951

View attachment 442954


This might be okay to illustrate the basis principal of the ironless motor; however, to effectively analyze an ironless motor assembly, nonlinear FEA with the appropriate BH curve must be utilized. Magnets in a motor assembly never have constant fields. The fields vary with position inside the magnet depending on the points on the BH curve. Twetety years ago FEM did nonlinear DC FEA and even came with an assortment of BH curves for commonly used magnets. The motor is a dynamic system and its more than just the DC flux in the gap and assuming nagnet height does not do anything. Nothing could be father from the truth! As I indicated within the first few posts, setting the operating point and magnet grade selection are critical. So this is simple. If the analysis is nonlinear, then a BH curve file is required and FEM will allow the user to load various BH curves. These are text files that can be opened and edited with notepad and they can be plotted with Matlab or Mathcad. Can you post a BH curve, either plotted or just the point within the text file? Every grade of NdFeB magnet has it own BH curve. My guess was N50 but it's just a guess. I have posted N48 below.

View attachment 442944

That image just has different colours for the different material regions. The contour plot looks like this:

 

[mwmkravchenko]

I am retired and I have not practiced in 10 years. So I don't have my software running. If there are folks out there that have non-linear electromagnetic FEA and could support this discussion that would be very helpful. The model is really simple 4 x box cross sections. NTK can you create a contour plot of the flux density inside the magnets (the cross sections) in the axial direction? Not the magnitude, the flux density, B in the axial direction. Can you plot the magnetic field strength, H within the magnets?

What BH curve should I use? My guess is N50. But what about the cryogenics? Forget that for now.

I could run it in FEMM 4.2 should you wish Steve. It shows you a 2D model on screen but internally FEMM4.2 models in 3 D. This is a fairly basic motor to model.
A very intelligent Hungarian programmer and I cobbled together a software suite from Open source solvers that is quite robust and very accurate when modeling loudspeaker motors and the soft parts.

 

[somebodyelse]

Frankly the reason I am here today is because the USPTO agrees that Borresen invented my concept of 2009 in 2019. I am pissed! When I get pissed, I get going.

Isn't that what Inter Partes Review is meant to be for?

 

[Pearljam5000]

6X 4.5inch ironless drivers + a tweeter

 

[smowry]

I could run it in FEMM 4.2 should you wish Steve. It shows you a 2D model on screen but internally FEMM4.2 models in 3 D. This is a fairly basic motor to model.
A very intelligent Hungarian programmer and I cobbled together a software suite from Open source solvers that is quite robust and very accurate when modeling loudspeaker motors and the soft parts.

Hi Mark,

Really glad you stopped by. Please create a FEMM model if you could be so kind.

 

[smowry]

Isn't that what Inter Partes Review is meant to be for?

I will look into this but I cannot afford to retain an attorney to challenge his patent. I am not interested in using a motor concept that was created for a tweeter on a 4.5 inch woofer. However you are obviously more knowledgeable in patent law than I. I had never heard of Inter Partes Review before your post. Are you an attorney?

FYI: That's an outstanding post! I love ASR.