EnABL Processes

[BudP]

Walsh termination

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Moderator Note:

The beginnings of this thread -- the 1st 68 posts have been copied out of 3 other threads.

Beyond the Ariel
OHM Acoustics "Walsh F" Speaker remakes
Help me kill a fostex artifact.

If some of the comments don't make sense it will be because they are out of their original context


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Hi All,

This is the beginning of a rather curious post. I have been bouncing around a few threads saying speculative sounding things about a speaker driver and associated baffle surfaces treatment, that does not look feasible, on first approach.

A moderator has agreed to create this thread, that has all of the pogo-ing posts in one place so everyone can doubt at once.

What I am portraying in these posts is a concept for controlling edged and smooth taper terminus zones. These zones are responsible for the bulk of what is wrong with modern drivers. They cause reflected standing waves, circulating Raleigh waves and diffractive emissions at the final terminus of a "speaker system". Almost all of these reflected artifacts are transient in nature. This means they do dissipate and without an extended dissipation period, due to particular materials used.

That their dissipation over time has a profoundly corrupting influence upon following sound energy and it's resultant reflections is quite obvious, when you get them to stop. What is not obvious is how pervasive the corruptions are. Speakers should theoretically provide infinite detail, complete with "musician applied color" and instrument induced transients and their resultant decays, all of them. Speakers should reproduce the sound field recorded, with enough spatial cues and time to arrival cues, to allow our millions of years old, audible threat assessment system, with it's semi autonomous correlator, to finish recreating the sonic event being reproduced with a fluency and ease that does not tire us nor force us try to hear beyond some irritating noise that interferes.

This EnABL process, portrayed in the following post series, does remove these transient artifacts, produced by uncontrolled reflections and refractions. This is not a theory. It works. It is also so good at this removal that it will not seem possible, for someone who has not tried it themselves, to believe. The qualitative statements you will find, as the braver and more adventurous DIY'rs try it out, will simply not be creditable. "Nothing could be that good" will be the thought and nothing could be farther from the truth, either. There are levels of treatment, having to do with how much your skill at hearing corruptions has developed, and, how maniacal your activities are. But just the most rudimentary attempt will bring huge benefit to your reproduced sound. The real learning process, after a few treated speakers, will be in determining how much is enough.

I will be providing a guided tour through treating a pair of Lowther drivers. I know next to nothing about these speakers and their idiosyncratic sound, but I am certain to horrify those who are devoted to these devices. I apologize to you for this insult, but the person who owns the Lowther’s has asked politely and pretty forcefully that I proceed.

I will not be making any before and after Quantitative measurements. I am going to leave that to you folks who really do know what you are doing in that realm. Of course that means you will have to treat a set of drivers, or two, but I will not be upset about this. I will suggest that very little, of what is a profound qualitative improvement, is going to show up in the usual tests. At least that has been my experience, but, I am not qualified to do these tests anyway. You who must, should probably start qualifying the results of this process with a CSD plot.
There are two documents on line you can refer to.
The first is posted at Positive Feedback Online, Issue 21 at this url http://www.positive-feedback.com/Issue21/standingwaves.htm This will give you some ground to understand from and does provide a truncated CSD on a cone, "phenolic ring" tweeter at the end of the paper. Take special notice of the last pair of comparisons, this is what all of these words are in honor of.
The other is a patent document found at where ever you can obtain these from. I have never been successful, but then, I have the original hardcopy and so my motivation has been low. The patent number is 5,304,746 and it is currently in force, to the extent that I have millions of dollars just waiting to be spent on lawyers to enforce it.
So read on and enjoy,

Bud

(original post that above was inserted into follows)

Just in case you folks would like to step outside of the normal mass loaded cone termination regimen, please read this.

http://www.positive-feedback.com/Issue21/standingwaves.htm

The entire process was developed on a pair of Ohm F's and turned them into point source radiators, in a spherical sense. Also eliminated the reflections from the materials joints.

Bud

 

[BudP]

Secrets revealed

Crank up the WD 40 machine... here we go.

The first thing done was to remove all of the internal foam damping material. Second was to "letter" this block pattern , on the inside, using a flat acrylic model paint, right out of the bottle . This paint was applied directly to the titanium surface, aluminum surface and the bottom edge of the paper using Speed Ball A series, 1 to 5, calligraphy pens (the ones with a bent tip). The pattern template is supplied by printing on a sheet of paper, with printing and scaling provided by Corel Draw 4 or later. Cut the round pattern out, apply it to a thin cardboard stiffener and you are ready to "letter". The scaled pattern needs to be a bit smaller than a direct size, so it settles deeper into the top of the cone than where you are going to apply the pattern. This pattern application location is the bottom edge of each material stage. The same process is applied to the outer surfaces, in the same places, though moved up a bit due to the glue overlap. In this case the ring printed by Corel needs to have the center cut out and it needs to be slightly larger than the applied pattern so that it will sink towards the bottom, underneath where the pattern is to be lettered.

The pattern does not need to be particularly precise so skill needs are rudimentary and if you can hold a calligraphy pen you can perform the needed activity. Best to learn on cheap paper speakers first. And, you will be amazed by how good these things really are.

Application of the conformal coating, on metal surfaces is only over the pattern, not the entire metal surfaces. For the paper you can apply it over all of the cone material, for much deeper bass as it will stiffen the paper, or just over the pattern for what has always been available.

Since this process adds mass only on the transverse wave boundary layer, the amount of mass needed is infinitesimal compared to what is needed to mass damp the entire driver surface. This is true regardless of materials or frequencies being controlled and works as well in infrasonic as it does in ultrasonic, though the pattern is comprised of really tiny blocks of printed material in the ultrasonic realm.

To experiment with dome tweeters and other small radiators you will need to acquire a range of technical lettering pens from the days of yore when mechanical drawings were done by hand on vellum paper. Since this is a scalar architecture, with the same number of blocks for any given ring diameter you will need some pretty fine points and to cut the acrylic paint with water by 10% or so.

Yes, I am the mad fool who developed this, so I can provide you with a Corel file should you be interested in experimentation.

The claims I can make are quite extensive but the one that I really like the benefits of the most are the resulting infinite resolution of micro dynamic signals and the addition of many dB of headroom before compression sets in. All of the information revealed by the process has always been there, just unintelligibly presented as noise, due to corruption by standing waves.

Also, what is really being done here is to speed up, or slow down, the wave front speed over the entire surface, to exactly that speed needed to emit a coherent wave front into the air, as the impulse traverses the driver surface. The white paper tests, shown on the last two pages, clearly indicate that more energy is getting off of the driver surface, before the final terminus of the tweeter in use.

Bud

 

[c2cthomas]

Hi Bud

Thanks for the info - and I personally would replace the phrase "mad fool" with "mad scientist". I'm a bit familiar with standing wave theory in airfoil designs - but that is a different application. In electronics and waveguide theory there are some applications especially used in phased array radar systems the traveling wave tubes - again a different application. But air can be considered as a "fluid" when considering the physics involved with compression and resistance to flow. The added problem with air is that it can be compressed where most fluids cannot. I understand your theory on the break-up of the standing waves with your EnABLE pattern which you have patented and I have taken the time to look over your patent at the USGPO. I took particular interest in the application of the pattern around the baffle of the speaker and on the surface of a dome shaped speaker - which might be of use in this type of project. I also took note of the math calculations used in the patent and considered doing just what you said when you stated to draw it up Coral Draw (or something of that sort). I was considering printing it out on a thin sheet of vellum and adhere it to the speaker cone but I was unsure as to what type of material was being used to perform the actual mechanical breakup of the standing wave. I was considering using some speaker dope and powered felt as a place to start and was also considering material to use on the speaker baffle - perhaps some cut up sections of felt pad. But 1st things 1st - I think Covey said that - Build a reference speaker as a base from which to work and compare and mamboni's design seems to be a very good starting point. I should also point out that I haven't been fooling around with audio since the mid 70's when I used to repair them. I used to have a complete set of those nice pens when I designed PWB's the old fashioned way - with Bishops red & blue tape on a precision grid - then I touched up the photo dropouts with the pins.

Isn't something similar to your EnABLE pattern being used to breakup rip tide currents? I seem to remember something like that in Popular Science. BTW - have you ever looked into an application for use with SONAR - might be something there.

 

[BudP]

damping vs damping

I have not used any materials except the acrylic paint to create the blocks with. I suspect others will work as this does seem to be a local mass interruption, in an area that is inherently low mass and high energy per sq CM. The paint has always performed well on every surface I have tried, and since I have been fooling around with this since 1973, there are a lot of treated surfaces by now.

That it works on incident surfaces is also quite interesting. Relieves the normal diffraction at the edges of boxes and other deflection plates. Use in horns and drivers is quite noticeable with more energy density in the air, very few reflection artifacts in the horns and a general lack of horn "cry" due to the standing waves that populate most horn flares.

With the average speaker box treated and all drivers also treated the box disappears from the sound field and no artifacts give rise to it's reappearance, and the perceived sound field is immense. Done properly there are no "hot spots" at any frequency and images with multiple frequencies or a range of frequencies extending across more than one driver are pin point in their placement, with respect to our ear / correlator / conscious comprehension, and do not wander due to frequency changes, even across differing types of radiators.

This is of course some kind of "speaker holy grail" too good to be true and you can be sure that Not Invented Here has been the only response I have received from those very knowledgeable folks practicing their own form of this black art. To very good results by the way as the EnABL process has far less effect upon modern speakers than it did 30 years ago. Now it pretty much just accomplishes the original goal of eliminating transient standing waves, by making it impossible for them to form in the first place, without altering any of the other tonal and transient events in any way I have been able to measure. Certainly distortion plots and the included traces of various even and odd order HD are not visibly altered.

I was cautioned many year ago by a naval engineer not to mention Sonar in conjunction with this process as the government would and easily could co opt it, without paying me a penny and enforce my silence about the process and it's benefits.

Thanks for your thoughts, it is refreshing.

Bud

 

[mamboni]

Hello Bud:

You're EnABL approach to transverse wave termination is ingenious. Forgive my simplistic analysis, but your pattern of squares is behaving like a virtual diffraction grid, cause optimal phase cancellation in as much as the speed (and phase) of the wave are shifted as it traverses the stiffer lower impedance square-treated cone surface. Now, this in effect blurs the virtually cone-surround boundary, making the cone appear as an infinitely long transmission line. Your solution is elegant and simple. And I think I would be most interested in utilizing it in a future Walsh driver. I admit that I do not understand how the distribution of the squares is calculated for the woofer cone however.

I wanted to discuss the felt approach I implemented vis-a-vis a comment you made about it being mass loading. When I conceived the felt approach, the idea of adding progressive mass to the cone to achieve wave termination and simulate an infinite transmission line was the intuition. However, I discovered something unexpected - the felt fabric is incredibly light. In fact, after the felt treatment the Fs of the woofer is lowered no more than 1-2 hz. Yet the wave terminating ability of the felt is extraordinary. I believe there is something else at work here, far more important than mass: the felt consists of thousands of fibers. I believe the fibers are acting as a huge surface and providing for a much more efficient coupling of vibrating cone surface with air. Normally, the cone-air interface is a very inefficient due to the very different acoustic impedances of solid paper and air. The felt dramatically increases the effective surface area of the cone - many tines over. The best analogy I can think of is the small intestine, which to the naked eye is lined my a smooth pinky mucosal surface. But, under the microscope the surface is covered by billions of tiny hairs (villi), and ultrastructurally, each of these villi have thousands of microvilli. The result is that the effective absorption area of the small intestine is increased over 100-fold.

One might ask: if the felt is increasing the efficiency of acoustic radiation from the cone surface, why does the woofer not become louder per input watt? The answer is that all these thousands of fibers each cause random sound cancelling phase shifts and are behaving more as a low Q reactive impedance. In a way, the felt fibers are acting as thousands of tiny versions of your EnABL squares. Of course, the low Q results from the fibers coupling well with air and efficiently wicking acoustic energy away from the cone into the air.

Based on listening, the felt surface treatment seems exceptionally selective in damping out the resonant stored energy and perceived white noise that normally plagues the paper cone in its upper pass band. The felt has little effect on the woofer when operating in it's lower pistonic band. The result is an incredibly quiet soundstage and exceptional clarity of midrange separation. Of course, this must be heard first hand to be judged for oneself. Do you per chance live near Pennsylvania?

 

[BudP]

Mamboni / EnABL

I have no doubt that you are actually providing what my EnABL process simulates, an infinite boundary to a cone terminus, by actually providing an essentially infinite boundary layer.

Very clever, and the first specific instance of the use of this powerful lever, an effective control of the boundary layer, to enforce this effect I have seen other than the process I worked out so long ago.

Hooray!!!!!.

A number of folks around the commercial side of the speaker industry are becoming aware of the problem with boundary layers and that the boundary layer is the only place to control it. As an example Dynavox uses filled polypropylene cones in their large diameter voice coil woofers. Of course this solution just eliminates any sort of boundary layer active control without actually eliminating the transient ringing, just it's duration.

I suspect that a combination of our processes would either be a spectacular success or an equally spectacular failure. I think we should collaborate.

Your description of the silence of the sound field around instruments, with no loss of reverberant information nor micro dynamic detail is very familiar to me. I listen to it almost daily, as I work with speaker cables and interconnect cables that can be tuned for how much dynamic color they preserve and, with excess, add to the energy passing through them. Both of these tools aid greatly in the design and vetting of the audio transformers that I am currently in the middle of the third round of R&D activity on.

Should we ask for a separate thread to continue this discussion on? I suppose we will have to have some private communications also.

I live in the Seattle area and am elderly enough that I do not travel much, so we may never meet. But what fun!

Bud

 

[BudP]

Thomas,

I do have an Auto Cad 14 lisp program already written, that will turn cone outer diameter, inner diameter and length between termini into a pattern set, that could be used for this purpose.

I was originally going to use this, laid out flat, to make a photo sensitive negative from, so that I could make a photo resist print on silk screen, use that to print on paper material, (Hemp?) cut them out and form them into cones. With a bit of edumacation the program works quite well.

I did forget to mention that applying the pattern at both terminus edges of a treated surface is very beneficial. I wonder what a pattern of Mambonis's neat felt, applied to the EnABL pattern would provide?

Bud

 

[BudP]

Many subjects

Thomas,

Your idea of a "tacky" template is quite a good one. The silk screen sock notion was always just too complicated and rife with Murphy crevices to really interest me. You seem to have enough enthusiasm to carry this off so let's try out your idea.

We need to find out what file format Knight prefer their information in. I will assume a vector file and I can produce most of them. What we also need to pursue is a correct template for the cone dimensions you are working with. Simple measurements of the diameter of the two openings and the length between will suffice for a first attempt. Then some small modifications to the thickness entry in the lisp program should give us a pattern for both sides of the cone.

A pattern applied to the "listening" side of a driver will provide about 70% of the control that treating both sides does. The energy pulse that traverses a free air diaphragm is reciprocal in nature. What you do to one side does have consequences for the emissions from the other side. This is true for all cone materials I have worked with, even the dead plastic diaphragms.

If you will email me at the location noted in my bio and provide pretty tight dimensions on the cone you have in mind, we can proceed. If the tacky template idea works out, it will provide an avenue for DIY's to tackle other cone types and sizes.

I was never able to successfully devise a program for projecting pattern blocks onto a dome surface, though there are still only two pattern rings needed. The solid geometry calculations just overwhelmed my poor brain when I attempted to translate the needed description to Auto Cad lisp.

So, feel free to charge ahead, I will be happy to provide intellectual, practical and even some financial support for the project. This is, after all, a public domain intellectual property and the only key I hold, how to make it work in reality, can be had for allowing me to participate in any commercial venture that arises. I am not a particularly greedy person and the patent runs it's course in six years in any event.

Bud

 

[c2cthomas]

Hi Bud,

Mamboni specks a PIONEER W25GR31-51F 10" BUTYL SURR WOOFER (http://www.partsexpress.com/pe/show...tnumber=290-088) back in post #33. This woofer is desirable for a number of reasons but chief among them is it will go to at least 6 KHz - where most 10" woofers stop around 2K. Also the cone is of butyl construction which is important for its "sound". Not to mention that it is not an expensive speaker - so even if I destroy a couple while I'm fooling around it's not going to break the bank. I think that we may well need to treat both sides of the cone surface because using this woofer to simulate a Walsh device we will be listening to the sound produced by the back wall on the speaker cone and working around the spider most likely will block access to some areas of the rear surface. What are your thoughts on alignment requirements between the patterns on the inside versus the outside? I would think that the patterns should overlay each other and that misalignment could make things worse. On the other hand if the patterns are offset it might serve to breakup the edge reflections even more - and that could be a good thing!

Speaking of Walsh (and for that matter DDR, who make a similar transducer) have you shared your design with them? You don't need to answer that - I'm not trying to pry - it's just a suggestion. I would think that they might show an interest in the technology. I can see the "new and improved" ads now - "Our new speakers use the EnABLE technology (patented) that allows for - blah, blah, blah - your listening pleasure". At this juncture I'm not concerned with dome tweeters because I will be using a Heil AMT on the high end. I'm not interested in going commercial (famous last words) been there - done that - got the t-shirt. (One part of my business brain is sketching out a production line in the garage - the retired part of my brain is saying NO - this is a HOBBY - HELLO .)

I'll send you a PM "test message" to establish contact and exchange some ideas - I don't want to hijack the thread.

 

[BudP]

Spiders everywhere

Thomas,

From the EnABL point of view you can ignore the spider, but the basket legs need to be dealt with. Usually just the conformal coating material will suffice. Once the wave front has terminated from the bending board as a coherent wave, it exhibits the same properties as "live" sound does, in that it will wrap around and cross over disturbances without tonal alterations becoming readily evident. I am reasonably certain that the wave front being emitted by a Mamboni treated cone will exhibit these same characteristics.

I suspect that a combination of EnABL and Mamboni treatments will work very well together. One "complaint" that I always had with a fully EnABL treated Walsh driver as you would find in a set of Walsh two speakers,or any other type of cone after treatment, was that I had to be extremely careful with the reflections from within the box as the driver becomes very transparent to those, since they are just as phase coherent as the emissions from the front side. I suspect that the felt triangles will help to suppress that back wave sensitivity.

Bud

 

[mamboni]

Thomas and Bud:

I'm reading your discssion with great interest. By the way, I am a physician by trade and training and not as proficient as you guys in the technical and engineering aspects. I would most interested in what you guys come up wiht and hope you will post some photos.

Thomas hit on all the key features that determined selection of the 10" Pioneer woofer. The thing is, as you guys have noted, loudspeaker manufacturers experiment with all manner of exotic materials and coatings in an effort to eliminate boundary effects/cone resonance. But, the technique we are using here requires no exotic materials, just a modicum of engineering and design. And in the bargain, one has converted an inexpensive woofer into one that can match or exceed the expensive exotics with the fancy composite cones and proprietary viscoelastic coatings. Now I do not have the setup to do detailed frequency reponse and waterfall plots, and I suspect Bud does; but, based on my hearing the felt-treated woofer sounds amazing clean and delicate, as if all manner of energy storage has been eliminated. But, one would need measurement of a treated woofer to prove this. If this is true, then these post-production mods might have a market, either as ready-use modified woofers or kits for the user to apply the treatment himself. Imagine the advantages: a woofer that is non-resonant and resistant to cone breakup would require no crossover, and would sound superior to almsot any "coventional" woofer. It could be a boon to hobbyists who want to build a phase and time correct loudspeaker and eliminate the crossover.

 

[BudP]

Utopix,

Ummm.... acrylic floor wax.... industrial strength. I buy mine from Micro Scale Products, called Micro Gloss. The real deal is that it needs to exhibit transverse wave energy transfer at speeds faster than that of sound through air. Most varnishes and lacquers will not do this and you can clearly hear the difference, but I have never found a way to measure it.

The paint I use to letter the blocks onto a driver surface is made by Poly Scale corp. Flat Finish #404106. Both of these materials will be in any decent hobby shop that sells plastic models and some HO scale train items.

Mamboni,

I am delighted to see the interest you have stirred up. Have you thought about using your process on more conventional speakers? Still placed on the non free air emitting surface, I suspect that a considerable improvement in midrange driver clarity might result. We may be stuck with just the EnABL process for dome, cone and linnaeum style tweeters... though I have seen the odd Walsh based tweeter show up. Not a drawback. Certainly a conventional speaker setup, with your pattern on the back of woofer and cone midrange, my pattern on the front to lightly correct whats left over, and an EnABLE'd tweeter, will rival the Ohms for clarity, depth of field and sheer musical beauty. And that is saying something!

While it has taken some number of years to accomplish I have a conventional system that will easily outperform my original treated Ohm F's in all of the categories you would care to list, so I am sure your idea can be so applied and between us we may just get as close to perfection as humans in the real world can accomplish.

Bud

I am still very intrigued to try both processes together, I do sense a possibility of synergy.

 

[BudP]

Getting you some tools

Mamboni,

I have to reinstall Auto Cad 14, after that herculean task is accomplished I can plot a set of patterns based upon large end diameter, small end diameter, height of cone and thickness. This plot will be on a flat piece of paper that you can then roll up into a cone.

Many years ago I wrote a lisp program for taking this data and creating this flat drawing , with all blocks, and proper spacing from edges included.

If there is interest I will make the lisp program, which runs in Auto Cad 14 and possibly later versions, available for free. With that and a Corel file I can provide you can make cone templates that will show you where to put the blocks and scaleable Corel circular templates, to guide your placement of blocks for a given pattern. There are always two patterns for a cone surface and the smaller pattern can be merged with one that will be applied to a center dome for a three row pattern with the first and third rows on the dome and cone respectively and the middle row in the joint between.

This process will take a day or so to get up and running again and I will then ask you for dimensions for a cone that interests you, though I may not be able to plot the file, as I no longer have a large format plotter. I am sure you can find someone to help you with this. The Corel file does require Corel 6 or newer to allow you to open and scale the circles of blocks to a useful size, but, again this should not be hard to obtain as most printing companies can print from both Corel files and Auto Cad DWG files.

Bud

 

[BudP]

Mamboni and all,

Here is a sample cone you can cut out and make into a cone, either an innie or an outie. As you can see the block size in a ring set changes with the actual diameter that it must cover. The lisp program that I have performs all of these calculations and draws the resultant conic section as a flat surface. I have converted it ot a jpeg format for your convenience

The specifications need to be for:

The large cone opening diameter, or the diameter just at the lowest edge of the surround where it overlaps the cone.

The small cone opening diameter, or where the center dome actually touches the cone surface.

The material thickness, a guess will do.

The length down the cone surface from the surround lower edge to the top edge of dome attachment, on the cone.

Obviously these dimension call out specs are aimed at the normal face of a cone speaker, but I am sure all of you can see how to use the dimension call outs for the backside or Walsh side of the cone.

Dr. Mamboni, when you have a set of dimensions you want to experiment with, and I would strongly suggest a small diameter cone, like a 6.5", so we can keep the conic lay out sheet on a letter size piece of paper, I can provide another of these, close to correctly sized and the Corel block rings that you would use as a location template, to actually letter the blocks in place on the cone surface.

This is not as complicated as it sounds here. The teenagers I have taught this to take about 30 minutes to completely treat a cone, on both sides, with blocks and conformal coat.

Bud

 

[BudP]

Hi Mamboni.

I did not really intend that one as a stencil, cutting all of those squares would take at least three times longer than just drawing, or "lettering" the blocks in place using the traditional method with a calligraphy pen and a circular chart of block placement, based upon the diameter and size found in the type of "stencil" you have now seen.

Thomas and I are converging on a method for stencil making with either etched block pattern circular strips, that wrap half way around the cone for one set of block rows, with a 3M tack adhesive on the back and a sponge to dab the openings with, or a laser cut vellum stencil, with the same tack adhesive and 1/2 cone circumference strip scheme.

I am proposing just what you portray, EnABL on the outside and Mamboni on the inside, just how and where you place it now. I do not think that a heavy application of EnABL control will be needed at all. You will almost certainly see benefits in extended high frequency range, roll off smoothness and quite possibly a 3 dB increase in overall efficiency, though that is never a given, unless you do not want it to happen.

I have attached a sample flat block guide that would be used to guide placement of the blocks with a lettering pen.

 

[Utopix]

BudP

May I make a suggestion for the stencil for large diameter woofer(like the 10" woofer that mamboni already made). You can print on a single sheet of paper only a small portion of the stencil, not the complete cone. (See attached picture).

As you can see, we this new stencil we only have to paint the blocks from 1 to 10(big blocks and small blocks) on the woofer cone, after that we just move the stencil to the right and align the 1-2 holes of the stencil on top of the already paint block number 9-10 (for alignement). And we move on until the entire woofer cone is done. Unless the block alignement must be precise within a 1/100 th on an inch, I think that this method is valid.

With that in mind, it is easy to imagine that you can generate (with your program) on a single sheet of paper many different template for different woofer.

Just a thought!

 

[BudP]

Utopix,

Quite an excellent thought. Are you ready to give it a try?

Using your method we can make a flat pattern that sits just below where you will letter the pattern. A good convention is that the blocks closest to the cone describe the blocks right next to them and then you use the lower blocks already on the cone to describe the length of the whole upper block set and just get as close as you can for the correct space between the upper blocks. I usually do two lower blocks and then the upper between them so I am able to clearly see the pattern I am creating. This will be good enough, I assure you.

We might still want to have the upper, or smaller diameter pattern be a full circumference, with perhaps a single slit so you can get it on to the cone and then tape it back together and let it settle.

Just as with Mamboni's treatment there is a lot of forgiveness for small errors.

If you have access to a copy of Corel 6 or newer, and I am certain it is available on eBay, I can post the latest flat twin ring file and you can size it to fit your needs exactly and print out a full sheet with as much of the diameter of the cone you want to work with, or as much as the letter size paper will hold. I do believe you have found the key, thank you.

Bud

 

[rcavictim]

Has anyone thought of looking at the ripple pattern produced by the Enable array when used at the far end of a shallow water ripple tank? Remember these simple analog/mechanical devices used before computers?

Although the claim of performance is not in question here at all I think it would be interesting to see the way it works. While at it a triangular edge could be tested as well.

 

[BudP]

Utopix,

Sorry, I was so tired last night that I did not notice how far I had strayed from your idea, until this morning, when I awoke from a dream about being lectured for short sightedness.

The one piece panel that you are talking about will work. I suspect it needs to be made from vinyl and might best be made with a sign makers vinyl cutting machine. although I have never even seen one of these to know if it will cut rectangles in the middle of a space, rather than have it slice to the spot and then cut the rectangle.

I am willing to provide a specific pattern size for you to experiment with. Because of the number of times that you will have to peel and reattach you may need more than one application of the 3M tack adhesive Thomas was talking about.

Again I apologize for stomping all over your idea last night, I will probably do it again though.

Bud

 

[BudP]

rcavictim,

I did perform an ad hoc wave tank test many years ago, and made simple line drawings of the results. If you would like to analyze them I will dig them up and put them into a pdf for you to look at. I will caution you that the effect they portray caused my high energy physicist friend who witnessed them, to claim they were the same as magic... something happening in front of his eyes that he not only did not understand but could not believe he was seeing.

A short description is a set of blocks, meaning two from one ring and a center set from the adjacent ring were cut from two pieces of 3/8" thick wood, as fingers sticking out from the edge about 1/2 inch. In other words every thing but the fingers was cut away and the resultant blocks followed the pattern array dimensions shown in the patent.

These block holders were sized to fit stiffly between the narrow walls of a 8 inch by 4 foot fish tank, half filled with water, about 6 inches deep Fluorescent lights were positioned underneath, lengthwise, and a piece of white cardboard was hung a couple of feet above the tank, to show the shadows of any wave action in the tank. A 6 inch wide dipping paddle was used to agitate the water at one end of the tank and the pattern holders were positioned six inches away from the dipping end of the tank, with the fingers into the water about a quarter of an inch. I make no claims about scientific rigor being used here, I just wanted some idea of what the heck was going on!

When the dipper was agitated, mostly up and down, without the pattern blocks pushed down into the water the expected choppy surface with waves that eventually became quite chaotic in direction arose after a few moments of agitation and took a few tens of seconds to completely dissipate and allow the water to become calm again.

When the pattern was shoved into the water that quarter inch and the dipper agitation restarted, a checkerboard pattern arose between the pattern and the dipper and from the other side, seemingly in perfect sync with each of the dipper strokes, a smooth, straight line of wave appeared from the pattern edge shadow, flowed to the end of the tank and dissipated without any obvious reflections. This pattern of activity held until you stopped dipping and the last wave occurred with the last dipper stroke and the water surface quickly became calm again.

All of this was clearly shown on the white cardboard surface as shadows. There was a pretty wide range of dipping cycle speeds that provided this effect, as the dipping was done by hand. I did not explore the out of range effects at the time so I cannot report on the failure modes.

Round pattern dots work fine, down to about 4 kHz and out to beyond my ability to measure. Below this vague cut off point the square edged shape begins to become necessary, though these "square" edged blocks usually are not all that square edged, but definitely not round either. I am quite certain, through some experimentation, that many "shapes" will work, some better than others at certain frequency ranges on certain materials, other than paper.

The rectangular in spirit blocks seem to work across the frequency band though at this late date I no longer try to make rectangular shapes on small high frequency drivers. Round dots, thankfully, work here very well. In fact I just treated a set of Pioneer piezio electric film tweeter to use to top off the high frequencies from the Radio Shack Linnaeum, baby cheek, soft horn wall tweeters I use. These only provide signal out to 13 kHz and the Pioneer half round "can" shaped devices are on a 0.22 mfd induced slope to match and extend out to 30 kHz or so..

Bud