EnABL Processes

[BudP]

Hi Lynn,

When I asked about the potential benefits of "speeding up" a front side surface, as opposed to the back side, I was thinking about the Mamboni process of small triangular light felt necklaces applied at the cone terminus, on the back side, just as he does now for the Walsh style woofer drivers, and the EnABL process on the front side. Using a conformal coating that will transmit boundary layer energy faster than the speed of sound through air will allow a fairly large increase in useful emitting surface when the EnABL pattern is underneath it to kill the transient standing waves. The three together seemed likely to be beneficial here in dipole land.

I am going to assume, without ANY proof that the Mamboni process on the back side will allow us to naturally bend the null zone back like a skirt and if we provide a skirt plate for those waves to attach to we could probably shape the entire dipole emission into the room with that lever.

Do not count the Walsh bending event out with respect to dipole emission either. When EnABL treated, the things emit as true point source radiators, right up and over the magnets if those surfaces have also been eliminated as diffraction edges. Scary looking in a living room filled with wife... anyway.

I am also interested in a Walsh style upper mid and tweeter in combination with a modified dipole emission lower mid and bass driver setup. That led me to question whether any of our participants had investigated sounding board shapes other than the usual straight edged planar surface. I have seen one interesting one, from the land of OZ participants, that shares its perimeter shape with that of musical instruments. I wonder if that French Curve derived edge treatment helps to kill transient standing waves. Seems likely to me. See BobF's pics here.

http://home.vicnet.net.au/~macinc/clubproj.htm

Bud

[BudP]

ScottG,

I did apply that EnABL pattern to a set of horns once..... To some Radio Shack systems with a high efficiency 15 inch woofer, a mid and a tweeter horn, not time aligned in any sense. The untreated speakers were not much fun to listen to.

The cone, front plate and horns were all treated. The results were odd.

The result was a VERY forceful speaker with razor sharp detail and near perfect time alignment, as the EnABL pattern appeared to enforce this condition onto the overall sound, even though all of the drivers were mounted flush with the front cabinet surface.

Did not make them any more pleasant to listen to though, but they were a lot more efficient and would play quite a bit louder than before so their new owner was very happy.

Did this for some teen owned boom boxes too, with the same results, but was always worried I would have to face the irate townspeople with their pitch forks and torches so I stopped doing that. Then the cars full of woofers and amps began to show up and I knew I was again safe.

Bud

[BudP]

In another thread Janneman has taken the lot of us to task for not understanding the operating principles that are the basis for a true Walsh driver and our explorations into them.

See here: my 14 inch full range speaker!

For my part, I agree that we should give more reverence to Lincoln Walsh's groundbreaking insights.

In fact all drivers work within the parameters that Mr Walsh provided. No driver is a "piston" at any time other than it's single natural frequency of mass resonance. All other frequencies are produced as some form of bending wave.

Below the "pistonic moment" frequency the drivers are literally flapping, like a wet sheet in a wind storm, the energy into the surrounding air. As their bending length becomes an ever decreasing fraction of the wave length they are creating they are able to bend less energy into a compression wave and become less efficient.

This is a bending line length VS frequency problem, not a cone piston movement problem. Walsh, with the help of OHM corp. solved this issue with a tall cylinder with an exceptionally long bending line VS it's diameter. The OHM F and A were notable for how much "information" was contained in their low frequency performance. The result of bending the very low frequencies into the surrounding air in a much less compromised phase and time signature format, with respect to the shorter waves also bending into the environment

Above the pistonic point waves also bend into the environment but it is a ripple with a period length less than the bending line length of the driver. As Ohm discovered, a more bending compliant material was required to allow this ripple to create a pressure wave in adjacent air, remain in phase with the pistonic and lower frequencies and still provide enough lateral stiffness to physically enforce true pistonic movement and drive lower frequency, fractional wave, bending into the environment. Hence their use of stepped materials, an initial titanium cone, a follow on aluminum cone and a final paper cone with mass loaded termination slots cut into the paper and filled with an RTV compound. The type A was all metal in construction.

I do not know who did the actual empirical extrapolation of Walsh's theory into an engineered device, but their solutions were brilliant and their mentation was utterly without boundaries.

As for the two termination schemes found in this thread, both work within Wash's theories and both will provide a superior termination to a Walsh derived bending line, or, the more typical short bending line, pistonic theory, speaker driver construction.

The only lack I find in either Walsh's theory or Ohm's implementation is a misunderstanding of the mechanism by which energy travels through a permeable medium, regardless of which side of the pistonic moment it resides on. Please go here and read this for a much deeper treatise on this topic.

http://www.positive-feedback.com/Iss...ndingwaves.htm

Mr Walsh did not look closely enough at this aspect, that since boundary layer physics sprouted in the late 80's, is now called "boundary layer phenomena". I suspect that he was aware of the event, but either did not comprehend it's potential importance to the expression of his theories, or was concerned that a discussion of such a heretical concept, in concert with his already deeply heretical bending line concept was not going to be beneficial to acceptance of his ideas.

It is a shame because had the Walsh / Ohm F's been terminated with a device that actually controlled the boundary layer emitting surface of the bending line driver, the Ohm F and follow on speakers would be a far larger force than we now see.

Thank you Lincoln Walsh, EnABL would not exist if it were not for you. And, thank you OHM and attendant engineers, without you I would not have had a platform upon which to develop the EnABL process.

Which, by the way, works on drivers that try to conform to the pistonic model precisely because they are Walsh bending line drivers and only pistonic at one single frequency.

Mamaboni's discoveries also are a superior termination scheme because they take into account the termination requirements of a Walsh bending line and a third vector boundary layer that emits while the wave front crosses that bending line. They work on pistonic based drivers for exactly the same reason mine do. Lincoln Walsh was and still is correct in his upset of the pistonic apple cart.

Bud

[ultrakaz]

Hi Bud,

I'm curious about your system (post #112). I don't want to hijack this thread, but could you elaborate a bit more on it? Specifically, what were your performance goals and what is/are important/necessary qualities for your speakers to reproduce.

Your description of the sound of your system is very similar to Lynn's description of how a system sounds at the highest level. And yes, please post a picture. Thank you.

[BudP]

ultrakaz,

Well, I have the same goals as Lynn, Romy the Cat, Island Pink, the moderators of this forum, you and very many others involved in DIY audio. I want a performance in my living room that satisfies my musical needs. I am used to extreme detail, correct depth of field, jubilant dynamic color as added by the musicians, a natural micro dynamic coherence and it's resultant stage setting for the musical event.

At the moment I am working on developing an amp and preamp of pretty simple circuit design and outstanding usefulness in developing audio transformers. The speakers have not changed in five years, except that I remounted the Linnaeum tweeters down on the speaker box and a recent trial addition of a Pioneer half can super tweeter, that may stay and may not.

I have recently discovered a method that allows me to uncover the back half of the musical notes, with the sort of clarity that the front half exhibits. This has added a depth of note decay and a coherence to chord structures in orchestras and piano's that I have not quite gotten used to yet.

Mostly I am just working towards a time when I have no further complaints with the equipment and I can explore the music I have collected, without constantly being distracted by my correlator warnings going off about this or that uncategorized and potentially dangerous noise.

I have to warn you, the speakers are not impressive looking. They were originally designed and built as workhorses, to allow me to audition the R&D from my transformer explorations. Just as the user adjustable dynamic color, true Litz wire, cables were invented, so I could listen for faults without having to worry about spurious cable colorations or loss of information content.

My contributions to this forum are meant to be a stepping stone for other people to use, so they might feel confident enough to explore and enjoy what this odd EnABL pattern brings to the reproduction of music, which is all I really care about

Bud

[BudP]

ultrkaz,

Email me about the wires. Email c2cthomas about the Mamboni / EnABL treatment details.

The back half of the notes comes from having a method of preserving micro dynamic detail, the E Field portion of that detail, which becomes B Field. I do it by providing low threshold, dielectric dipole attached, sheet oriented electrons, on the ground plane. You can do this with poured ground planes and guite a lot of PCB varnish, or some huge stranded wires, 8 gauge or more and a measured amount of dielectric material both surrounding the wires and melted into them. You might even be able to use low threshold voltage Teflon, audio bipolar capacitors shorted to ground on both ends. What ever method you use will entail providing ground plane storage for an abundance of electrons so they do not return to service ground or further.

The research I have done on dielectrics in transformers, audio cables and now ground planes has shown me that while we have a very excellent handle on signal side electron manipulation we really have ignored the manipulation of the ground side signal of our equipment. I do have a solution, it is easy to apply, but it is very much applied voodoo physics.... more or less like the EnABL process is.... makes perfect sense after you understand how it works and why you might need it.

So, email me and we can talk about your interests.

Bud

[BudP]

dineubec,

Pretty neat stuff. I have had thoughts on this sort of speaker for years but knew better than to attempt so much precision wood work.

The EnABL process will work on all of the drivers and all of the surfaces but will be quite an undertaking to do. I would recommend that you finish first. Then begin to categorize what you do not find satisfactory in the actual audible performance. My method here is to start with the fundamentals first, up to 1 k or so and listen for inaccuracies in the left hand of piano's and all bowed and plucked strings larger than a violin. I will often deliberately reduce very low frequency performance at first just to help clarify what is actually going on.

What I listen for is a garble of tones, at any particular frequency. Once I am familiar with what I am hearing I add a higher frequency driver and listen to how it modifies what I am familiar with. This sort of listening teaches me what is incorrect in only one driver and what is a multi driver problem.

Were these my speakers I would use a Vifa 3" mid in place of the metal dome and phase screen. The EnABL process can not control "systemic" resonances, those caused by materials and physical obstructions used in driver construction. I think it likely that you will find a garble from that mid dome that is directly related to the material used and treating with EnABL will only make it more pronounced, because everything else will work better around that frequency band..

Does not mean that you should change your plans, you may have already worked around what ever difficulties this particular driver exhibits, and they all exhibit many problems.

The EnABL process will ease the transition off of the round to square baffle and likely can control those surfaces and force them into phase and time coherency. The tweeter would work well with the process but you will have to disassemble it and treat the backside of the dome also. Neither of the dome drivers can be treated with other than a pen and guide pattern process, at least from my experience.

I will post any other thoughts I have on your thread.

Bud

[Lynn Olson]

Originally posted by BudP
Hi Lynn.

I wonder if the enclosures you mention could be terminated with some modification of the Mamboni pattern, perhaps extended into three dimensional shapes of some size and made from a material that eats energy by vibrating small kinked bits of fiber?

There is a material of merit, the replacement carpet underlayment used by auto interior restoration folks. About an inch thick, with a tightly interlaced body of various length and diameter, kinked, moderately stiff fibers and small pieces of a rag like material. Has a shorter, more densly packed face, on one side, with the other face more open and with larger kinked fibers. Easily the most linear damping material I have found and good from infrasonic to about 2 k or so. Very linear in this range too.

Perhaps a Mamboni ring applied just before and entering into the peg board mesh area?

Bud

Hmm, I'd like to hear more about this interesting material. Where do you get it, what is it named, etc. "Good from infrasonic to 2 kHz" sounds pretty awesome to me, and certainly good enough for the purposes of edge termination on the HF dipole and bass units.

Reflecting on the previous mini-essay, we see the same kind of topological tricks used in microphones to create the desired polar pattern. Omni mikes have small enclosed chambers on the back side of the diaphragm, dipoles are left open on both sides, and cardioids use damping techniques on the back side of the diaphragm - and for variable-pattern mikes, anything from variable shutters to two sets of diaphragms and an electrical adjustment.

The real issue is edge termination, regardless of enclosure type. Loudspeaker designers who avoid the time domain like to dance around this, but I now think it's a combination of mind-set (freq resp uber alles), unwillingness to work in another domain, and unfamiliarity with the tools of the time domain - MLS, TDS, etc. The frequency-only mindset has significantly retarded progress in loudspeaker design over many decades - I can now understand better why Dick Heyser of Cal Tech met nothing but 100% opposition in his native Los Angeles, the home of Altec, JBL, and Cerwin-Vega. His work met a more receptive audience in the UK and Europe, but I'm still surprised how alien working in the time domain is for many high-end designers.

When you visualize the driver as a wideband pulse-emitting device with a dipolar radiation pattern, it's easier to see what the enclosure is really doing - storing and re-radiating energy. There are two things making this challenging relative to other fields: the awkward requirement for three decades of bandwidth - extraordinarily wide by RF standards - and the extreme dynamic range of the ear, which is very sensitive to the faintest decay products. The only reason we don't object more to the grossly artificial sound of hifi systems is we've been listening to these things for a long time.

[BudP]

Geoff,

May I suggest that you think about how you can get the energy off of the baffle plate without attenuating it, without mass "STORAGE" damping, without any ringing of transient standing waves, without any diffraction artifacts and in phase and time coherence with the expanding polar wave front from the driver. That will get you much farther than damping of any sort and I believe is the point Lynn has been pushing towards with his comments. Unless you have a "perfect" damping scheme you will have reflected energy.

You might also look at the thread on Walsh drivers for some interesting information on wave termination from a surface without damping.
OHM Acoustics "Walsh F" Speaker remakes

For your phase plug concern I would personally urge you to make a smooth flat surface with a flat acrylic paint, or study and apply either the Mamboni or EnABL edge termination process, one will apply, and will satify your concerns.

Bud

[BudP]

JoninCR,

You might want to re-read the last few pages. They aren't actually about bass monopoles at all. Some cardioid bass was mentioned by Lynn, Gary Pimm's flat to 16 Hz system specifically, and then some slight discussion of how to use a specialized, infinite edge simulation pattern, with multiple, in this case likely hundreds, of ports in an attempt to make a perfectly terminated rear bass chamber for possible bipolar operation, as an alternate to the cardioid bass was also mentioned. I am not at all sure why more bass might be needed, Gary Pimm appears to have shown a clear path for integrating bass and bipolar mid and upper drivers.

Your point on the amount of power that is available at the null zone of a driver is important to note. There are some edge terminations that remove reflected energy from the cone edge, being experimented with in another thread here, the Walsh thread after page 6.

I can report that the EnABL process narrows the null zone at the periphery of a driver to just a handful of degrees. Would that help or hinder your damping procedure as shown in your pictures? This process will also eliminate edge diffraction from a baffle, regardless of it's shape, and even large radius edge contours can benefit from a less lossy termination.

The Mamboni process spoken of in earlier pages in this thread, will also remove edge diffraction by making the terminus infinite. The use of both of these tools to control driver and baffle plane reflections and energy storage, without significantly damping any of the active or passive surfaces with further energy storage mechanisms, might interest you in your future experiments.

Bud