XBL patent, prior art from 1976?

[Snickers-is]

I really can not find any difference between the claims of Mr Wiggins in this patent from 2006:

Patent link 7,039,213

And this patent from Dallas company Babbco Ltd in 1976, figure 9:

Patent link 3,983,337

The last one (from 1976) describes the use of twin coils in combination with a single gap to provide the same effect as what is described as the XBL technology. However, this section is interesting:

It will also be appreciated that the relations of the magnetic field and coil can be interchanged so that the magnetic field is divided and the coil is continuous, with precisely the same theoretical and practical results. Such a structure is indicated generally by the reference numberal 130 and FIG. 9. The center magnetic pole 132 may be identical to the magnetic pole 26. The outer magnetic pole 134 has an annular opening 136 in which an annular groove 138 is cut to form two equal subsections 140a and 140b. The total axial length of the two subsections 140a and 140b may be equal to that of the outer magentic pole 28 plus the space between the subsections. The coil 142 is mounted on a coil form 144, which may be identical to the coil form 44. The coil 142 has an axial length equal to the distance between the centers of the sections 140a and 140b of the pole, so that the sections 140a and 140b are centered on the ends of the coil. Variations in the axial lengths and spacings of the pole sections 140a and 140b relative to the coil 142 will result in force curves identical to those illustrated in FIGS. 6, 7 and 8. Additional analysis will show that all other arrangements result in non-linear sections for the force curves. It will also be noted that the relationship of coils 104a and 104b is such that the force can be made linear indefinitely by providing additonal magnetic fields of the same length spaced apart by the distance M. Such an arrangement provides no practical advantages, however.

Here is Fig 9:



And here are Fig 6-8:



Have I missed something or is this just another prior art patent?

[GM]

Wouldn't surprise me, there isn't much WRT speaker design that's been invented in recent decades, just lots of new patents based on expired ones. One company in particular has made a very lucrative business of doing it.

WRT the Babb, I have a couple of small Lorelei 'full-range' drivers with a usable 1.2" [30.48 mm] Xmax and by 'full-range' I mean it, it has an almost completely flat usable 20-20 kHz BW that with at least a 400 W power handling capability at very low distortion based on Alan Babb's in-home testing. For sure, the 250 W I had available at the time I was using them didn't even warm them up except when playing some pipe organ symphonies or action movies at fairly loud levels.

It had a lot of promise and a pity he wasn't able to continue to develop it due to having to sell the company after the Fla. hurricanes ~ destroyed their primary market, though he did do at least one major revision that I didn't get to audition, and the new owners apparently got taken out of play by the last couple of economic down turns shortly after the buyout.

GM

[Snickers-is]

Sounds like a really impressive driver. Please feel free to post more info and pictures in this thread if you feel like.

[tb46]

Hi,

Yes, that's very interesting. As to the Xmax thing, just when you think you had a good idea the ancients seem to always beat you to it. :-)

Regards,

[thune]

It appears the 1976 Babb patent (3,983,337), describes an "annular" gap in the top plate only (in combination with a CYLINDRICAL pole piece). Where as, the XBL patent describes gaps in BOTH the top plate and the pole piece.

In my mind this would qualify as a non-obvious refinement.

[Snickers-is]

I disagree.

First of all, the use of T-shaped pole pieces, meaning pole pieces which do have a larger diameter in the gap(s), was at that point of time a well known method for tuning the end contour of the gap flux profile.

Secondly, the essential function of the technology does not change when the diameter of the pole piece is reduced outside the regions of high flux.

What is also important is that the patent in general describes the function of the 1976 Babb patent and not the function of the grove in the pole piece itself. The descriptions of even thickness pole pieces in the 1976 Babb patent is a part of the sliding teflon bearing and has nothing to do with the gap technology.

The XBL patent completely presents the technology described in Fig. 9 in the 1976 Babb patent as the new "invention", and the 1976 Babb patent is refered to only with a description of the dual coil configuration. If the XBL patent was about the pole piece, then that would have been described as the invention. I think the mentioning of a groove in the pole piece is completely a coincidence, and just proves how obvious that tweak actually is.

[tinitus]

that grove looks like outside the gap, at the end of center pole
and looks more like a farraday shield ring

I think the 'XBL groves' are inside the gap

or I may have misunderstood the whole thing

[thune]

Snickers-is,

While I did find it odd that the XBL patent only makes reference to the split-coil embodiment of Babb's patent, I think the XBL patent centers on the pole piece grooves:

Whereas prior attempts to resolve the conflicts have focused upon reducing the mass and/or altering the suspension system and/or fabrication and mounting of the core and/or dividing the coil in half, it has been found by the inventors that utilizing what hereinafter will be called a "split gap design", wherein a groove or series of grooves is placed in the exterior portion of the core and a similar groove or series of grooves is placed in the interior surface of the plate, allows a much shorter coil to accomplish the same purpose with little or no modification to the remainder of the speaker structure.

claim 1 on XBL:

...field having two or more displaced regions of greater intensity, wherein both the top plate and central pole produce the regions of varying magnetic intensity, those regions having magnetic flux in substantially similar directions, and separated and surrounded by regions of lower-intensity magnetic field...

claim 2:

An apparatus of claim 1, wherein the top plate and center pole include opposing surface grooves.

The XBL patent also extends the idea to >2 gaps.

I'm willing to be wrong. To really read these patents would be a half day job, that Babb patent is a monster.

[Snickers-is]

Tinitus: are you refering the groove marked 146? If so, it has nothing to do with the discussion.

Thune: I also noticed that they extend the idea to several gaps (two or more). Using 6mm gaps and spaces in combination with 12mm coil gives:
1 gap excursion = 12mm * 0,25. Coil coverage: 0,5. Gap coverage: 1,0. Total coverage: 0,5
2 gaps excursion = 12mm * 0,75. Coil coverage: 0,5. Gap coverage: 0,5. Total coverage: 0,25
3 gaps excursion = 12mm * 1,25. Coil coverage: 0,5. Gap coverage: 0,33. Total coverage: 0,167

It was when experimenting with the difference between 2 and 3 gaps I discovered the patent conflict.

Your quote shows basically the same as the claims, a specified groove in the pole piece that could be a coincidence. What is not a coincidence however, is the specification that the groove in the pole piece and the top plate needs to be opposing.

Yes, the Babb patent is extremely complicated. I believe you would never get approval for all of that in a single patent today.

I am not sure about this either (that is why I started this thread), but it seems to me as if the groove is insignificant to the patent.

[tinitus]

Originally Posted by Snickers-is

Tinitus: are you refering the groove marked 146? If so, it has nothing to do with the discussion.

ah, I see the grove #138# now
thanks

well, it does indeed look 'similar' to XBL

did I see XBL design with copper in the groves, somewhere ?

btw, picture shows underhung voice coil