"Breaking Speakers' Hoffman iron law"¹: Dual Force Cancellation Subwoofers Vs Magnetic Negative Springs.

[GGroch]

Found this earlier patent by Matsushita/Panasonic (US 6,574,346) on their concept of negtive stiffness (similar to Brane's "magnetic negative spring"), which purpose is to increase the equivalent internal volume of the speaker cabinet.

I think Braine's driver works very much like Matsushita's this dual permanent magnet design, but with the addition of IC controlled electromagnics that keep things stabilized by instantly adjusting the "springs" relative to volume and frequency.

If it works you theoretically could get more real bass out of a small portable speaker. The increase in efficiency could allow for sealed enclosures (which the Braine seems to be) instead of ported/bass radiator designs commonly used to save power.

I would love to see one of these on Amir's spinorama.

MKVH produced this video advertorial video

 

[GGroch]

The original Brane X thread here links to a techradar article with internal photos.

 

[Alfredo02]

Point is that expert reviews classify the two brands as best in class regarding bass extension, both using limited power 50 or 60 watts and both having as said before much better bass extension than competitors. Curiously both at similar price, around 450 eur.

This is why Amir review comparing both models would be ideal

Comparing the results of both brands that use the same principle, both using closed - non vented - cases, taking advantage of opposing forces, the first Sonos with two opposed woofers with a pane in between, or Brand Audio obtaining the opposing forces via magnetic negative drivers.

 

[FrantzM]

Thanks but the smell is still there.

+1


Peace.

 

[Duke]

... overall just get the waft of bs.

Thanks but the smell is still there.

+1

Do you both really understand this patent application sufficiently to make a valid claim that it's BS? If so, can either of you explain the reasons why you think it's BS?

It's easy to sit on the sidelines and cast aspersions at something that is outside one's range of knowledge and experience, and I really hope you guys aren't doing that. I hope you took the time to understand the patent application sufficiently before impugning the integrity of the inventors, and I hope you will share that understanding with us.

 

[Duke]

The original Brane X thread here links to a techradar article with internal photos.

Very interesting! I hadn't seen the magnets attached to the voice coil former depicted in the patent drawings that I looked at; there were multiple documents with multiple drawings and I didn't look at all of them.

My understanding is that in the production version of the invention, the magnets progressively increase the effective BL as the voice coil goes beyond the rest position, and this increase in the effective BL is tailored to offset the air spring inside its sealed enclosure, such that the enclosure's internal volume is not the significant limiting factor that it ordinarily is, at least up until the excursion limits are reached.

Normally a spring exerts a force towards a return to the rest position (the air spring inside the enclosure for example), and in this application we have the additional magnets exerting a force that tends to increase displacement away from the rest position, hence the descriptive term "magnetic negative spring".

 

[Wolf]

The "magnetic negative springs" appears to be a version of a dual gap-motor, where the double voice coil is operating within 2 separate motor gaps. Frankly, this has nothing to do with elimination of vibration, and everything to do with controlling the driver enough to prevent overexcursion. JBL GTI woofers are an example of this. Essentially, the forward gap is reversed magnetic polarity compared to the rear typical motor. This way, the negative spring action of the gap opposed to the cone's current motion magnetically brakes the motion of xmax Via one of the 2 voice coils.
The new Mofi 888 from Andrew Jones are another example of something similar, but in a reduced package size. He stated that there are 2 magnets in the frame, mounted opposing poles, and one voice coil moves within the split gap between the 2.

Edit: the "attraction" is the mini magnets in the former being attracted to the other 2 large voice coil gaps as they approach extreme xmax limits, and try to overcome the inherent volume air spring the driver fights against. However, the "repel" is likely either the second ring of mini magnets or the combination of the mini magnet rings and the opposed coil gaps. It really is not that hard to understand what it is they are doing. Caveats; The Mms is higher for the driver, but you need mass to tune low. The dual gap motor likely has more inherent inductance and therefore higher back EMF, unless the effects cancel each other. Cost is likely higher to manufacture with very likely tight tolerances.

Without using a second equal driver to oppose the force of the first as the OP questioned, there would have to be another equal mass with motion opposed to that of the first driver.
The only way I've thought to accomplish this involves using an opposed vibrational transducer or actuator not unlike a bass shaker or buttkicker device.

There really is no other way than making the cabinet ultra heavy to minimize the acceleration the force applied to the high mass enclosure.

 

[GGroch]

I hadn't seen the magnets attached to the voice coil former depicted in the patent drawings that I looked at; there were multiple documents with multiple drawings and I didn't look at all of them.

The above referenced Matsushita patent was from 2000 and has expired. That patent's background of invention states:
"Regarding the bass reproduction of a typical speaker, there is an inverse proportional relationship between the cabinet internal volume V, bass reproduction limit frequency fc, and efficiency μ. Therefore, as commonly known, it is very difficult to reproduce lower frequencies efficiently in a small cabinet.

It has been also known that bass reproduction performance can be improved without concern for these constraints if negative stiffness is used to decrease air stiffness in the cabinet and increase equivalently the internal volume of the cabinet. Actually, however, there have been no suitable methods to achieve this purpose."

This correctly contradicts the earlier post that bass response is limited almost entirely by speaker cone size. Cabinet size and amplifier power matter too particularly in acoustic suspension designs. If it works, I would think this technology could be used in home/auto subwoofers.

Matsuchita let the patent expire, so one assumes their design also was not suitable for the purpose.

 

[Duke]

The above referenced Matsushita patent was from 2000 and has expired. That patent's background of invention states:
"Regarding the bass reproduction of a typical speaker, there is an inverse proportional relationship between the cabinet internal volume V, bass reproduction limit frequency fc, and efficiency μ. Therefore, as commonly known, it is very difficult to reproduce lower frequencies efficiently in a small cabinet.

It has been also known that bass reproduction performance can be improved without concern for these constraints if negative stiffness is used to decrease air stiffness in the cabinet and increase equivalently the internal volume of the cabinet. Actually, however, there have been no suitable methods to achieve this purpose."

This correctly contradicts the earlier post that bass response is limited almost entirely by speaker cone size. Cabinet size and amplifier power matter too particularly in acoustic suspension designs. If it works, I would think this technology could be used in home/auto subwoofers.

Matsuchita let the patent expire, so one assumes their design also was not suitable for the purpose.

The increased moving mass from the magnets makes me think that practical applications are probably limited to subwoofers. I can see this technology potentially having a significant impact on the subwoofer market.

I can imagine the buildup of heat inside an exceptionally small enclosed airspace being an issue in a high-power application, and one way to prevent that would be to mount the woofer "backwards", with the motor on the outside of the enclosure. The exposed motor could be concealed by mounting the woofer on the bottom of the enclosure, recessed into the bottom as needed. Another possible solution would be a metal heat sink that conducts heat away from the motor to the outside of the enclosure. I think Wayne Parham of PiSpeakers holds a patent on such a device, which IIRC was shown to be effective in preventing voice coil overheating in horn-loaded subwoofers, and this approach might result in a more compact high-power application of this technology.

 

[Chrispy]

Do you both really understand this patent application sufficiently to make a valid claim that it's BS? If so, can either of you explain the reasons why you think it's BS?

It's easy to sit on the sidelines and cast aspersions at something that is outside one's range of knowledge and experience, and I really hope you guys aren't doing that. I hope you took the time to understand the patent application sufficiently before impugning the integrity of the inventors, and I hope you will share that understanding with us.

Personally just going by the company's marketing/description. A patent application isn't always helpful, or meaningful, and I'm not a driver designer. Seems the more you guys analyze it the less special it is in any case.

 

[Duke]

Seems the more you guys analyze it the less special it is in any case.

How so?

 

[Chrispy]

How so?

It seems more a variance of existing tech/design, nothing particularly unique the way I read it.

 

[Duke]

It seems more a variance of existing tech/design, nothing particularly unique the way I read it.

Fair enough. I read it very differently, as you probably guessed.

As a speaker designer who juggles the kind of tradeoff this invention addresses, I'm impressed with the creativity of the inventors, as I have not previously encountered a technology that does what the magnetic negative spring apparently does. If you're interested I can try to explain it.

 

[Chrispy]

Fair enough. I read it very differently, as you probably guessed.

As a speaker designer who juggles the kind of tradeoff this invention addresses, I'm impressed with the creativity of the inventors, as I have not previously encountered a technology that does what the magnetic negative spring apparently does. If you're interested I can try to explain it.

I'm game if you are. Be gentle.

 

[Duke]

I'm game if you are. Be gentle.

Thanks - I will do my best! I have to run now but will be back later tonight.

 

[GGroch]

Brane is not claiming marginal improvements based on tweaking existing technology. They claim: "A tenfold increase in sub-bass sound and a hundredfold increase in sub-bass efficiency—increasing performance without increasing size or power consumption."
If performance improves even 1/2 of what they claim that would represent a major breakthrough in driver technology.

At this point I am more skeptical of whether they can make it work. The initial design was shown at the 2023 CES and they are only now shipping in small quantities. So there must be some issues they needed to address and their may be others found by the first users.

 

[Keith_W]

If you're interested I can try to explain it.

I'm interested too! I must confess I looked at this and couldn't make sense of it. I thought it sounded a lot like a passive radiator but then what do I know.

 

[Alfredo02]

I've seen Andrew Jones explanations about the Mofi 888, and it explains with exemplar simplicity the principle of the double magnet, and certainly has a strong similarity with Brane Audio solution, maintaing a long coil and a small gap, having two magnets with opposed polarity in order to cancel flux modulation, reducing changes in the magnetic flux in the gap, helping the magnetic field in the gap to remain constant to ensure consistent speaker performance and improving efficiency in low frequencies.

 

[GGroch]

I've seen Andrew Jones explanations about the Mofi 888....having two magnets with opposed polarity in order to cancel flux modulation....to ensure consistent speaker performance and improving efficiency in low frequencies.

My understanding is:
While Jones/Matsushita/Brane designs all involve two sets of permanent magnets, the goals are different. The Mofi 888 uses a ported cabinet and from your explanation it appears its primary goal is to better control the driver's function on long excursion. This could lower distortion and allow somewhat higher output.

Matsushita/Brane add the additional goal of overcoming some of the negative forces inherent in putting relatively large displacement drivers in small sealed enclosures.

The Brane design has 3 sets of magnet motors. 2 using permanent magnets (which may work similarly to Matsushita/Jones) plus a third set of IC controlled electromagnets to keep things in allignment/under control. Brane claims this allows for far higher output/efficiency while letting smaller speakers take advantage of the inherent benefits of sealed cabinets.

 

[FrantzM]

Do you both really understand this patent application sufficiently to make a valid claim that it's BS? If so, can either of you explain the reasons why you think it's BS?

It's easy to sit on the sidelines and cast aspersions at something that is outside one's range of knowledge and experience, and I really hope you guys aren't doing that. I hope you took the time to understand the patent application sufficiently before impugning the integrity of the inventors, and I hope you will share that understanding with us.

No claims. I am an ignoramus. A patent however is not a proof. I'd prefer more than that, perhaps a White Paper.

I stand to be corrected.

Peace.