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Old 24th March 2007, 12:10 AM   #21
Utopix is offline Utopix  Canada
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Quote:
Originally posted by 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

I was just reading your first post and on this subjet and I was feeling that something was not clear. Sometimes its my writing that is not enough precise (English is not my first language) . Now,I think that we are in sync.

Thanks for your offer for providing some test pattern for me to experiment with. I will definitively come back to you on this subject in approx. 2 months. I have in front of me some major renovation project at my place and I feel that all my weekends will be spent on this. But beware, my interest in this topic is growing each and every day. Maybe I will be able to make some Sonotube enclosure before the end of April and be ready before May hopefully.

Cheers

Utopix.
 
Old 24th March 2007, 03:45 AM   #22
mamboni is offline mamboni  United States
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Quote:
Originally posted by 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
Bud:

It sounds like the blocks are acting as an interferometer or diffraction grid. I wish you had some photos - sounds fascinating. The ideal way to eliminate resonance is to introduce controlled destructive interference, a no efficiency-killing mass need be used.
 
Old 24th March 2007, 05:17 AM   #23
BudP is offline BudP  United States
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Mamboni,

I have always thought of them as a diffraction grating, but working with a vertical vector that is unusual in ordinary wave tank experiments, so, I had to modify my thinking just a bit.

We are both involved in this same process and using effectively the same tools, just arrayed differently and applied with different measures, same thoughts though. I am pretty sure that a combination of the two, along with treating both sides of the dome tweeter diaphragms with EnABL, will take your current 90% of the ohm model 5's performance and turn it into about 180%

I too wish I had some pictures of this earlier time in my life, especially one of Bill's face, the physicist friend, to show to you, when I asked him what he thought was going on.... a priceless memory I will carry to my grave.

Bud
 
Old 26th March 2007, 11:30 PM   #24
R. Jamm is offline R. Jamm  United States
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Default EnABLE pattern?

BudP

Iíve been following this thread and am in the process of building the Mamboni speaker system -Iím still waiting on parts and time (just got back from vacation) to finish it. Correct me if Iím wrong--your idea is to stencil in rectangular patterns (EnABLE pattern) with some type of acrylic model paint using a calligraphy pen on or near the top and bottom of the speaker cone.

- Also, you stated that this process should be used on the cabinet itself. Where would you place it?
- Is there an EnABLE pattern straight line stencil for this?
- Are the triangles the same size no matter what size the drivers are?
- Would this work on a cylinder cabinet like the one mamboni used (post #32)
- Is the EnABLE pattern different for tweeters? What tweeters would this work on?
- Do you have stencil for the different sizes woofer?
- Would the constant movement of the cone over time make the acrylic come off?
- Would you be sharing more information on how to get and use the EnABLE pattern and what are the best speakers this process will work on?
- Do you have any pictures of pass projects that you could share?

You stated that you have a conventional system that easily outperforms the Ohm F in all categories. Could you explain more and share the plans on how to make them?

Thanks,
 
Old 27th March 2007, 01:16 AM   #25
BudP is offline BudP  United States
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Default Whew.....

R Jamm,

You have the general plan correct and the pens have been my only means of applying the EnABL process in the past.

c2cthomas and I are collaborating on a stenciling method to replace the pen applied method for many applications. These stencil's will be available, in some DIY usable fashion, pretty quickly. We have plans and methods and even media trials in the works. If we are successfull you will have stencils that are designed for whatever woofer you are going to use.

This is planned with the thought of using Mamboni's felt triangles on the inside of the cone. I am pretty certain that this combo will be ultimately superior to the EnABL process alone. When both sides of a cone are treated with EnABL the cone becomes very transparent to back wave signals, emitting right through the cone and into the listening area. The EnABL process enforces a phase and time coherent wave structure to emitted information and that sort of energy is very good at remaining coherent, regardless of obstructions.

Using the Mamboni process right where he uses it now will help eliminate that possibility and still provide the needed "infinite" cone edge termination to the back side of the driver that allows the EnABL process to completely control the front side information emissions.

Just like the EnABL pattern blocks the Mamboni triangles probably should increase and decrease with the size of the cone they are applied to. I do not know if Mamboni has a rigorous analysis of this size change and I am not at all sure how much change is correct. We will all find out as we go along. I would personally scale the triangles in size, up or down, from his proven concept size found on the 10" woofers he is advocating using.

I would place the linear patten of EnABL blocks down the length of the tube, on opposite sides with a vector between the opposite lines at right angles to the listening area. This will attach all information expression from the tubes to this plane and will likely provide you with the leading edge of the perceived sound field too. I do this with ordinary cabinets, placing the pattern lines vertically, in the middle of the front to back dimension of, and down, all four of the sides. This helps to eliminate the entire speaker system as a perceivable sound source and in my system the speakers are sonically invisible regardless of where you sit, just like Ohm F's are.

I have never had the pattern made with acrylic paint delaminate or shed. I have had the conformal coat acrylic delaminate from the polypropylene surface of the Dynavox woofers in two half round areas, one on each woofer and about a 1/4" diameter. The coating has not come off nor has it altered the sound. It just lifted enough to show at these two places. This is the only event like this I have witnessed and because of it I now "tooth" the surface of plastic cones with 1000 grit sandpaper before applying the pattern and conformal coating. I do not think this will be needed on any other cone, dome, flat ribbon or horn flare material.

All speakers are the best for EnABL use. The process does NOT alter the speakers inherent qualities. As far as engineering concerns go the speaker just acts more like a theoretically perfect model would. I have applied the process to every type of speaker made and find that, while all of them share a clarity of detail, a hugeness and coherence of projected sound field, and, an uncanny rendition of musical colors and musician imposed emphasis, some manufacturers provide products that are just more interesting than others. Vifa, peerless, dynavox, seas, morrel and many others manufacturers drivers have been treated.

From that sort of list, my current system uses:

a 9.375" dynavox polycone woofer with a huge voice coil and a dis-assemble-able basket structure, that allows treatment on both sides of the entire cone surface.

a 6" dia Vifa dome midrange, with the inner perforated metal dome removed, the backing plate holes cut to one hole, the size of the magnet structure pass through hole. A very small back chamber (.4 liter as opposed to the 1.6 liter suggested) made from an ABS pipe end cap, stuffed with long fiber natural cotton that also extends up through the center magnet hole to form a small dome, trapped by a large opening plastic wire mesh.

two Radio Shack/Linnaeum polycarbonate leaf tweeters

a single Pioneer piezo film, half of a can shaped super tweeter, with the fine mesh grill removed.

All of the drivers and their mounting plate surfaces on the visible side have been treated with both the EnABL pattern and conformal coat material. Except for the Pioneer driver all of them have also had the EnABL pattern and conformal coating applied to the backside of the drivers. The pattern is not noticeable unless you look very closely but the very shiny surface of the conformal coat is quite noticeable.

On the Linnaeum and Pioneer tweeters only the pattern areas have been coated with the conformal coating. The dynavox woofer has a VERY thick coating, at least 10 mils, of the conformal coating just to construct a semblance of a boundary layer that will interact with the surrounding air. Otherwise it would be very clear and very dead sounding. As of now it matches the "speed" of the rest of the drivers exactly.

The system is sort of flat from 33 Hz to what ever the cut off for the Pioneer is. I am not as concerned with fractional octave to octave flatness as I am with phase coherence at the crossover points of 800 Hz, 4 kHz and a 0.22 mfd induced slope for the Pioneer tweeter. The entire tweeter assembly is impedance matched through a transformer, the design and manufacture of that sort of audio device is my livelihood, with a 2.8 db cut in turns matching ratio.

I can post a finished picture if anyone is interested, but it is not really impressive, until you turn them on and hear an orchestra embedded 50 feet into the back wall and from edge to edge and floor to ceiling of the room, without any hint of Hi Fi sound characteristic and seemingly infinite detail. Very nice to listen to, so long as I am not experimenting with new audio transformers that are not fully charged, or new DIY Litz wire audio cables, or the eternally demented "electron traps" I have been applying to the ground sides of all of my components, since discovering their characteristics.

Bud
 
Old 28th March 2007, 03:09 AM   #26
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Default Source of Colorations

Quote:
Originally posted by Cloth Ears
Lynn,

Leaving the more complex boxes out of the equation here, with regards the dynamics, do you think this due to the open baffle design itself (the ease of moving the cone only against air in both directions) versus conventional boxes (where the cone moves against an enclosed volume of air and only produces air movement from one side of the cone)?

What co-ax have you looked at with regards the primary driver? Something along the lines of a Tannoy, possibly?


Stored energy grossly degrades the sense of realism in every way: it steals dynamics, compresses and distorts the soundstage (which is why I always audition in stereo), and almost flattens the sense of depth completely. It's like MP3 with extra colorations thrown in free.

Unfortunately, there are many many sources of stored energy, particularly in the first few critical milliseconds. Cabinets have standing waves and wall flexing, horns have significant diffraction at the horn mouth (which then travels back down the throat and reflects off the phase plug), and worst of all, cabinet damping materials don't really work well below 500 Hz. All this is quite audible, particularly when you hear the coloration go away. This kind of coloration is the kind of thing you notice in the first few seconds of listening - and we only tolerate it because that's how 99.999% of speakers sound, and have always sounded since the Twenties.

Electrostats store energy too, although far less than direct-radiators in boxes or any horn. Where the electrostat falls down are a series of small mylar-diaphragm resonances between 3 and 10 kHz, which is noticeable on a MLS waterfall measurement (although easily confused by different arrival times from different parts of the diaphragm).

All drivers fall down here, compared to what can be done with plasma drivers. In my experience - speaking for right now, anyway - cabinet colorations are considerably worse than driver colorations, at least with decent-quality modern drivers. With an old-school driver like the Altec 604 Duplex, OK, I doubt that cabinets make a lot of difference. But when coloration levels go down, cabinet coloration becomes much more noticeable, and is very difficult to reduce. Exotic cabinet materials really only help a little bit, and introduce odd new colorations of their own. (It takes magazine reviewers several years to realize a new type of coloration has been introduced.)

As for new drivers, well, I've tried getting OEM Tannoys for many years, with no luck. As far as I can tell, Tannoy only wants to sell complete systems, without the nuisance-factor of the DIY market. Can't say I blame them. So I'm looking at prosound folks like 18Sound, B&C, and Beyma.
 
Old 28th March 2007, 04:14 AM   #27
BudP is offline BudP  United States
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Those of you who are thinking seriously about this speaker format might want to read another thread also, assuming you haven't already.

I start you off where the ultra low storage termination information begins and there are two very different methods for perfectly terminating a big driver without a bunch of storage mass.
OHM Acoustics "Walsh F" Speaker remakes


And yes this is a thread here in DIY

Bud
 
Old 29th March 2007, 10:03 PM   #28
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Default Here's Bud's EnABL Paper & the Mamboni Mods

Over at Positive Feedback magazine, my old stomping ground back when I lived in Portland.

As mentioned in earlier posts, the smoothness of the rolloff region is CRITICAL for high-quality sound, as well as a well-behaved radiation pattern in the crossover region. The EnABL treatment might be especially important for pro-grade coax drivers, which from the published curves have real challenges in the rolloff region (2 to 10 kHz).

The thread by Mamboni elsewhere in the forum about the Ohm F also some interesting felt-strip treatments for modern 10" woofers, allowing them to act as Walsh bending-mode transducers up to 10 kHz.

Both techniques would be useful for chasing out those nasty peaks and ripples in the 2 to 10 kHz region, and would certainly improve the sound of a coax driver. With dipoles free of box colorations, yes, you'll hear even small improvements in the driver.
 
Old 29th March 2007, 10:45 PM   #29
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Default It Gets Better

Further on in the Ohm F thread, Bud and Mamboni start collaborating together on combining the techniques. Following this thread to the end makes for some VERY interesting reading on sound propagation through solid materials and methods to control standing waves.

The Bud/Mamboni techniques are especially useful for any dipole speaker - once again, because these designs are entirely free of cabinet coloration, so you can hear the driver as as they really are. Yes, I guess you could combine a dipole with a Walsh - maybe if the baffle were slanted or curved towards the top - but you guys are on your own here. I still want to explore a really good coax - and yeah, not too many of these - on a dipole baffle.
 
Old 29th March 2007, 11:49 PM   #30
BudP is offline BudP  United States
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C2Cthomas,

We're waiting...........

I have attached a pic of how to treat a typical Walsh dome style tweeter and deflection plate with the EnABL process. Had to go digging in really old patent papers to find it too....

Mamboni

Our processes are being talked over, in another thread, quite unrelated to this one and by one of the most famous of all DIY proponents.

http://www.diyaudio.com/forums/showt...threadid=98969

We should join in and drag ole Thomas himself with us.

Bud
 

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