A technical discussion of the Borresen ironless woofer.

[racingpht]

These are my measurements, based on 145x145mm basket in the section view. FWIW
EDIT: I got the gap wrong. it is half as wide, so that would be 2.25mm or 2.5mm.
Corrected.
View attachment 444266

So ~9mm coil in 12mm "gap"?
Wonder how the BL(x) curve look like.

Seems like a short throw design to maximize BL. No wonder why spider don't have to support lots of throw?

 

[Snickers-is]

So ~9mm coil in 12mm "gap"?
Wonder how the BL(x) curve look like.

Seems like a short throw design to maximize BL. No wonder why spider don't have to support lots of throw?

I posted it earlier in the thread, based on the actual parts that were shown on a show some years ago.

 

[Snickers-is]

I've built 3D-printed double-reflex speakers, from what I see it seems not. Maybe they didn't render every detail in the cross section view.

The impedance curve looks like there's some small extra features, but in general don't look like a double reflex.

I guess from the design, it looks close to an extra acoustic filter to remove some mid-range leak from the huge port.

https://audio.com.pl/images/4/0/3/74403-laboratorium-borresen-m1-fot2.jpg

It looks like there is an upper and a lower chamber, connected by a short port.

 

[Sparrowlegs]

After reading your piece, Debunking Borresen's Wild Claims, and looking at the patent, I have two questions:

1. With the work you did to date and your comment about "software" (attached screengrab), what software did you use to simulate your findings?
2. Am I right in when looking at the patent, that items 16 and 18 are pole pieces, so that is where they've substituted the iron with something foreign (Silver or Copper)? If so this reminds me of some early work I was exploring in 2020 -

Sparrow Legs Speaker Design

This Omni directional speaker is now in audio heaven (MBL will be delighted ;)). Harvesting the magnets for the current rubanoid. The motor wasn't very good, wasn't designed with much thought,...

www.facebook.com

I presume you have access to something like Comsol? Anyway, if you need any help from a FEM-BEM point, I'd be willing to help, however, guidance would be required.

 

[René - Acculution.com]

View attachment 444582After reading your piece, Debunking Borresen's Wild Claims, and looking at the patent, I have two questions:

1. With the work you did to date and your comment about "software" (attached screengrab), what software did you use to simulate your findings?
2. Am I right in when looking at the patent, that items 16 and 18 are pole pieces, so that is where they've substituted the iron with something foreign (Silver or Copper)? If so this reminds me of some early work I was exploring in 2020 -

Sparrow Legs Speaker Design

This Omni directional speaker is now in audio heaven (MBL will be delighted ;)). Harvesting the magnets for the current rubanoid. The motor wasn't very good, wasn't designed with much thought,...

www.facebook.com

I presume you have access to something like Comsol? Anyway, if you need any help from a FEM-BEM point, I'd be willing to help, however, guidance would be required.

Looks like the software was Opera-2d?

 

[smowry]

Let's have a bit of fun and Hotrod the Borresen patented ironless motor transducer. I have previously reviewed the Borresen design and the "Barbie Spider" needs to go and the motor needs a bit of attention. The design can be further simplified with an increase in robustness.

Let's apply a round of DFMA and simplify the design while reducing the parts count, 9 Hard Parts + 6 Fasteners.

DFMA SUMMARY:

Minimize Parts

Standardize Components

Modular Design

Ease of Fabrication

Simple Assembly

Mistake-Proof Design

Design for Automation

Multi-Functional Parts

Consider Handling and Orientation

Reduce Fasteners

Below is a concept sketch of the hard-part module for the Borresen Hotrod, which has been renamed the "Moresense" transducer topology (patent pending). The "Unibody" hard-part module shows that less can be more and where the voice coil "talks" to the basket both thermally and electromagnetically. Keep it simple and robust. N45SH magnets are intended for high performance applications with safe operating temperature to above 150 degrees C.

8 inch Moresense Ironless* Hard-part Module Concept Sketch

7 Hard Parts + 0 Fasteners

*Ironless refers to all linear relative permeabilities, |mu relative| ~1 (assuming permeance coefficient >1and magnet temp is controlled). Iron and steel have nonlinear permeability with hysteresis characteristics.

Additional discussion can be found here. https://www.linkedin.com/feed/update/urn:li:ugcPost:7320557837279981568/

 

[Snickers-is]

Why not just jump to radial magnets and get far more linearity?

 

[smowry]

INNOVATION OR INVENTION?

• Almost Air Core EMI Drive

 

[smowry]

EMI Patents to date:

Sony has spent much time on R&D and they have several patents that discuss and develop the theory for the above.

www.freepatentsonline.com/5062140.pdf

www.freepatentsonline.com/6904158.pdf

www.freepatentsonline.com/7016515.pdf

www.freepatentsonline.com/7580542.pdf

Klipsch also has two Euro Patents on EMI drivers.

www.freepatentsonline.com/EP0453130A2.pdf

www.freepatentsonline.com/EP0453130A3.pdf

Then there is Tannoy’s co-axial.

www.freepatentsonline.com/4965839.pdf

I found another US Patent issued to W. K. Volkers in 1950.

www.freepatentsonline.com/2494918.pdf

I found another US Patent issued to S. E. Karlsson et al. in 1950.

www.freepatentsonline.com/2621261.pdf

Finally, the oldest Patent that I found was issued to A. Nyman in 1927.

www.freepatentsonline.com/1643169.pdf

The latest EMI Patent for a subwoofer motor is here.

www.freepatentsonline.com/US8009857.pdf

That's a lot of inventions (11)!

Now how many EMI transducers are utilized in commercial loudspeaker systems today?