[Brian Cheney]

Having received the go-ahead from "Sawtooth" Chris Regan, my patent attorney, I invite you to join me on a lengthy description and account of the US patent filed 10/13/05, with yours truly inventor and applicant, originally entitled:
"Planar Loudspeaker with Constant Directivity Full Range"

                         Background of the Invention:
It's Jan 10, 2002.  James Bongiorno and I sit at his favorite Italian restaurant in LV basking in the glow of the RM 40's winning the "Best of CES for High End Audio".  He doodles on a cocktail napkin and reveals the rough shape of a speaker enclosure. "Build this", he rasps, "and you will win again!"  The cabinet is that which I will spend the next year turning into the RM/X speaker system, and James is proven a true prophet in 2003 as the VMPS Alexis Park booth takes the big prize a second time.

Course you know this story since I've only told it a dozen times here and everywhere on line.

Matters did not conclude that evening with but a single napkin, there followed another.

This sketch was of a tall, narrow curved baffle covered with interlocking triangular planar mid/tweeters, placed apex to base.  There was also a unique arrangement of small woofers which would produce a hemispherical launch pattern for the bass.  "Build this", James intoned," and you will win again in 2004."  

Well again as you already know, that didn't happen.  After the second win the Tech TV judge told me in confidence we would never threepeat regardless of what I came up with.  Our 2004 entrant, the RM 30, finished 8th in the competition that year.

Still, the idea of a triangular planar driver intrigued me and would not leave my mind.  I went looking for a manufacturer and a partner.  In June 2003 we pitched Mark Shifter on the idea of Constant Directivity in loudspeakers generally and the trianular planar magnetic panel in
particular, and while Mark was most enthusiastic, further meetings did not lead to the hoped-for collaboration.  John Casler reported extensively on the initial contact on this very board.  The curious can search the archives from the summer of 2003 and find the threads.

The triangle is a great shape for a driver (and a cabinet for that matter, but for different reasons) because it narrows to zero width.  If it is made slender and long enough it will maintain excellent directivity with frequency over the range it covers--I was hoping for 300Hz to 20 kHz.  
It would have to be a few inches wide at the base so that the panel could start at that width.  It is the nature of planar panels that their excursion is essentially zero at the edges and maximum in the center of the diaphragm
much like a plucked bowstring.  There isn't any pistonic motion so paradigms that strive in that direction don't work with planars.  

As it turns out, the ideal shape for a planar from the standpoint of linearity
(flat amplitude response) is a large square, say 10x10", which is great for low distortion and LF extension but terrible for directivity.  I would not arrive at constant directivity with a driver which became rough and beamy at 900Hz.

Other shapes than the triangle would approximate the requirements for CD (I'll use this abbreviation for Constant Directivity henceforth, since it's the industry standard).  A diamond, particularly a double diamond, would do well; back to back double-D's (like the Dolby logo) and other wasp-waisted forms which begin wide and narrow to about 2/3" get the job done too.

I found a prototyper and made sample panels of various shapes and configurations.  Things did not go well.  It turns out asymmetrical traces on a rectangular diaphragm do not produce smooth FR or low distortion, and I was getting tons of both problems.  6% THD was typical, and linearity was poor below 2 kHz.  The undriven portions of the diaphragm undulated and flapped antiphase to the driven part where the triangularly shaped traces were etched into into the film (I used PEN).  It would do no good to have evenly dispersed sound no one would want to listen due because of roughness and high THD.

Over two years had gone by and I had nothing to show for them except rejects.  

(end of Part the First.  In Part Deux, I commit Ritual Harikiri in atonement for my failings).

[woodsyi]

Of couse, the triangle!

We gotta trade in the Neos for triangular ribbons? Is this going to lead to some permutation of Golden Ratio thingummyjig?  I can already see a  geodesic (a la Bucky Fuller) speaker cabinet with triangular ribbons coming.......

All right.  Tell us more.  You obviously failed at Harakiri, Brian San.  What happens next.....

[ctviggen]

Ah, triangles!  Who'd a thunk it?  It's interesting that Brian mentions triangular speaker cabinets, as my Linn 5140s are somewhat triangular (the back of the speaker is wider than the front).  Supposedly, this has benefits.  OK, I'm waiting for the rest of the story...

[ScottMayo]

YOW! Now I'm getting IMAGES of ODDLY SHAPED PLANARS and ANGELINA JOLIE!



(And a big wave to all the speaker manufacturers who are, with varying mixtures of irritation, disdain and extremely nervous worry, following this thread.     )

[John Casler]

Hi Guys,

Finally B, is able to release a bit of info.

Don't get hung up on the Triangle yet.

The main aspect is CD (constant directivity) and why that is a goal of speaker design.

B, will fill you in more as he continues the saga.

[csero]

Hi Guys,

The main aspect is CD (constant directivity) and why that is a goal of speaker design.

And what is soooo revolutionary in that?

[John B]

And what is soooo revolutionary in that?

No ones ever been able to accomplish it to a truely effective level.  Ever heard a 180 degree soundfield that doesn't disappear or localize no matter where you are listening to it in the room?  Ever walk up to your speakers and still hear the wholistic soundstage sound without anything changing with vocal and instrument placement, even though you're almost right between the speakers.  Ever sit directly opposite the right or left speaker and not lose your stereo effect by doing so?  That is what is so revolutionary; I've listened to a lot of speaker setups and none has ever done this.

[csero]

Ever heard a 180 degree soundfield...

Yes, but not from stereo. With 2 speakers in a stereo setup it is simply impossible (by all the knowledge we have about the auditory mechanisms), if the recorded material is not manipulated...

Ever walk up to your speakers and still hear the wholistic soundstage sound without anything changing with vocal and instrument placement, even though you're almost right between the speakers.  Ever sit directly opposite the right or left speaker and not lose your stereo effect by doing so?  That is what is so revolutionary; I've listened to a lot of speaker setups and none has ever done this.

This is not the problem of the speaker, this is an inherent fault of the 2 channel reproduction.
Wave field synthesys can do it better, but it has it's set of problems - besides the complexity.

BTW if you are between the speakers and the speakers are CD - not omni -, how can you get the same presentation, soundstage and timbre, unless you have excessive room reflections?

[dwk]

No ones ever been able to accomplish it to a truely effective level.  Ever heard a 180 degree soundfield that doesn't disappear or localize no matter where you are listening to it in the room?

Wait a sec - are we talking a 180 degree soundfield, or a controlled directivity soundfield?  

Geddes speakers do in fact do basically what you're describing, although I agree with csero that it's technically impossible to do exactly what you describe as it would require a device that gets louder with increasing distance. Now *that* would be a patentable device.

The idea is simple - if you have devices where the amplitude falls off uniformly as you move off axis (as Geddes waveguides are designed to do) then by crossing the axes *in front* of the listening position you create a situation where moving laterally the falloff of intensity from moving away from one speaker is matched by the falloff from moving off-axis from the other one. Not perfect, but generally effective.

Obviously the *idea* of constant directivity isn't patentable, so it'll be interesting to see what the details of the VMPS device are. In particular, what it brings to the table that a waveguide and/or say a waveguide+Unity arrangement wouldn't.  And before anyone says 'size', controlled directivity inherently requires size, so all you get to do is choose how to use it.

[ctviggen]

Although I'm going to wait for Brian to give more details (and preferably a figure or two), I can imagine two triangular speakers elements where it could be possible for one to move toward one of the two speakers and have relatively constant sound field, within some region anyway. However, it's a complex situation, and I'd rather wait for more info. before hypothesizing any more.

[ohenry]

Hi Guys,

Finally B, is able to release a bit of info.

Don't get hung up on the Triangle yet.

I was wondering how the triangle idea was going to be adaptable to existing VMPS and possibly other brand speakers.  So he's brewed up something electronically in the vein of room correction devices?

[John B]

I'll let B explain the details and science behind what I'm hearing from the beta pair I have; which from what B tells me is now improved...I'm hopefully 2 weeks away from getting my own Constant Directivity RM30C's

[Brian Cheney]

csero:

Instructions on "How to Flame this Invention" will appear after the last post announcing the product.  You're jumping the gun.  The words "constant directivity" do not appear in the disclosure.  It does not concern itself with SPL falloff rates or impossibilities like SPL levels increasing with distance.

The patent attorney advises me to announce the product and describe it without quoting or referring directly to the disclosure.

[csero]

I haven't flamed the invention as I don't know what it is. I just don't like  hyping.
Anyway the original title is graded back on the other forum:

The "Biggest Development" was meant as the Biggest Development in VMPS's technology, but no doubt, it is a "sought after goal of many if not most speaker designs.

[Brian Cheney]

The Geddes speaker I looked at uses an "oblate spheroid" (football shaped) waveguide infront of a coaxial driver.  Not at all the invention under discussion here.

[dwk]

The Geddes speaker I looked at uses an "oblate spheroid" (football shaped) waveguide infront of a coaxial driver.  Not at all the invention under discussion here.

No - I wasn't suggesting that the mechanisms were at all similar. Simply that neither 'controlled directivity' nor the relatively stable soundstage across a wide area were revolutionary. (BTW - it's just a standard compression driver, not a coaxial)

I didn't mean to sound dissmissive. I am genuinely curious. I've done my own experiments with Monsoon planar drivers in a 'waveguide' to achive relatively controlled directivity, and the results are extremely promising.  Of course, this is simply a reaction to the suggestion that 'controlled directivity' is a key result of the invention. If not, then obviously the observations are largely irrelevent.

[warnerwh]

Is this part in production? If so what's the ETA for shipping?

[klh]

Who cares whether he hypes his own product or not? I'll just check back next week or the week after and see what the fuss is all about. If the drama is still being played out, then I'll check in another month. Sure the hype is annoying, but he has all the right to do it, especially on his own forum.

[mattybumpkin]

Only two pages of thread on such an annoucement?  No flames, No in-depth discussion, this is it?????

Everybody watching "Desperate Housewives" re-runs???

I hope this new product/technology is all that, we could use something to look forward to.

I wish you much success,

Matty

[warnerwh]

We don't have anything to discuss. There's really no data to discuss and even if there were most of us are not technical enough to discuss it intelligently anyway.  After years of watching Brian's designs he's consistently done evolutionary designs and making large strides while doing so. Also he's never been a hype type person.  If you've ever talked to him you know he's as straight forward no bull shit type of a person as exists.  So whatever this is will be extraordinary or he's gone insane. Then again maybe it's both!