EnABL Processes

[BudP]

swak,

Absolutely, use the Mamboni process first. That 1.5 kZ peak is almost certainly a systemic resonance, likely related to the length of the cone from inner circumference to outer. The Mamboni process will help with this to a degree, as it will dissipate this energy and largely remove the edge terminus that is the probable cause here. I would use the PVA for the entire back side of the cone and then use it for the felt also. This will enhance the boundary layer on the cone backside and also enhance the effect of the felt in terminating that boundary layer properly. Expect to hear a big improvement with doing this.

Adding the EnABL process to the front will also help, as it will raise the amplitude of the surrounding frequencies somewhat and will smooth the following phase cancellations, as you go past the 1.5kZ peak. Very likely the driver will respond to a simple notch filter, after treatment, where before, the single notch would not address the roughness. You can expect to use a fair amount of Micro Gloss on these big cones so buy a few bottles.

I think you will be alarmed by how well this speaker performs when you are done.

Bud

[swak]

Bud,

thanks for your help, that is great news for me. As for the PVA, is there a particular one that I should look for. I am a little concerned about applying PVA to the whole back of the cone, its a non-reversible process and the drivers are not particularly cheap... but I am very tempted to follow your suggestion. The chassis would probably wont allow for a very consistent cover over the whole surface, would that be problematic? Should the PVA be thinned somehow or applied directly with a brush or piece of foam? And, what kind/make?
Thanks for your help.
Sebastian.

[BudP]

swak,

I have asked a friend, who used this material for a number of years on guitar speaker faces, for manufacturer and part number.

I have to report that I have had mental drift on the name, it is really Polyvinyl acetate not acrylic. It is an acrylic paint and is water soluble and when we used it at Nestrorovic Labs we just gooped it on the cone pretty thickly. You should ping Mamboni, or re read his descriptions to get a clearer picture of how to use it with the triangles.

If my friend still has any data I will pass it on, but I am pretty sure there is only one Polyvinyl acetate, though the well known Elmers White Glue has some additive that Mille Nestorovic felt made it less useful for speakers. Something about surface hardness with the Elmers product that he did not like.

Here are some comments on the material and it's additives.

A vinyl resin, one of the clear, water-white, thermoplastic synthetic resins produced from its monomer by emulsion polymerization. Polyvinyl acetate, abbreviated PVA , has the advantage over the other resinous adhesives in that it is available in the form of an emulsion that is readily diluted with water, is easily applied, and is safe to use because it contains no flammable solvents. In addition, there is no need to use preservatives or fungicides because it does not deteriorate quickly and is unaffected by mold or fungi. The emulsion does slowly hydrolyze, however, and should not be stored for more than one or two years before use. Freezing also destroys the emulsion; therefore, precautions must be taken to avoid exposing it to temperatures near or below the freezing point

The synthesis and patenting of vinyl acetate monomer by Dr Fritz Klatte in 1913, in Germany, provided the foundation for many valuable and now essential plastic products. He found that the catalysed reaction of acetylene with acetic acid gave a readily polymerised low boiling liquid (vinyl acetate) to yield a potential range of dense solid materials. These are now often denoted as (PVAc) or (PVA) polymers.

Klatte and others found that PVA was compatible with other polymers and plasticisers which could give valuable adhesives and coatings for cellulose and textile products. From c.1930 many companies manufactured a range of products such as PVA for liquid solutions and emulsions and hot melt adhesives and paints.

PVA is not an ideal moulding plastic so the development of many economic and attractive alternatives rapidly ensued based on the ability of vinyl acetate to co-polymerise with many other monomers. Hence, co-polymers with vinyl chloride, acrylic monomers, styrene, ethylene and others gave a great range of moulding, coating, sheeting, adhesives, insulating materials, etc.

Hydrolysed versions of PVA gave polyvinyl alcohol as a water-soluble coating and binder. The polyacetal derivatives of these have provided superior bonding and electrical insulation with good stability.

Emulsion paint and adhesive sticks, so readily accepted, are simple examples of these truly outstanding contributions to modern life.

Bud

[Bas Horneman]

What did you use as an applicator?

One of those calligraphy pens with the biggest tip they had. (Also suprisingly cheap to buy)

Were you able to get 36 sets of blocks?

Nope...did not know that was the aim. 31 pairs I got.... it's on a Bastanis Prometheus 12" "midband" supposed to go up to around 8k.

[planet10]

Originally posted by swak
As for the PVA, is there a particular one that I should look for. I am a little concerned about applying PVA to the whole back of the cone, its a non-reversible process and the drivers are not particularly cheap... but I am very tempted to follow your suggestion. The chassis would probably wont allow for a very consistent cover over the whole surface, would that be problematic? Should the PVA be thinned somehow or applied directly with a brush or piece of foam? And, what kind/make?

http://www.t-linespeakers.org/design/tweeks.html

I have used this stuff for nigh on 30 years now... as well as the benefits Bud described, it also makes the cone more opaque to sound coming back thru the cone.

I thin it and apply multiple thin coats with a brush. Thinned you need to be fairly quick with it as it will start setting up before you are done.

You might want to practise a bit on a piece of cardboard... i have no problem getting a reasonably consistent coverage -- especially on big drivers where you can easily get the brush under the basket legs. a number of thin coats also helps with this.

dave

[BudP]

Bas,

31 will work just fine. Will even roll off the highs slightly at about 8k Hz.
When you go back to the store with the A series pen tips for calligraphy, ask if they have Polar Coordinate Graph paper. Use of this and a set of mechanical dividers (compass with two needles) will allow you to make a pattern for any size driver, without having to resize one of my uploads in photo shop. You will find it's use very intuitive and helpful.

After determining an outer perimeter size with the dividers, you can make a couple of rows in pencil, just one or two blocks and choose a row one or two spaces smaller than the inner block row, make a full single row set and cut the paper to size to use for a template. This means that your pattern row should be about 4 rows, maybe 5 rows, in from the outer perimeter measurement. You will quickly be able to eyeball what you need to do.

This will be one of my early pictures for the Lowther processing which I will begin to post today.

Bud

[BudP]

Hi all,

Here is the promised Lowther beginning. The posted picture is of polar coordinate graph paper, applied to my purposes, the pens, Poly S paint and Micro Gloss coating materials. You can see a plan for a 12" driver, a Lowther size driver, a dome (with the blocks on the inside of the ring) and another small block ring. This is all you need, plus some scissors and a decent camel hair brush, to EnABL drivers of any size and configuration.

Bu

[BudP]

The link later on in this post should take you to a photo album that shows the pieces generated by computer fawning, that you do not really need to use, to EnABL a driver. Mostly I hope they give you some hints on how to use a guide and what it's placement, with regards to the actual painted blocks, should be.

The conic sections show where the actual blocks should be and the flat patterns show where the guides should be and the two together show how much above a flat guide to place the pattern blocks. All together, there will be nine EnAbl block rings.

The whizzer will have three rings at the top of the whizzer, two rings on the cone and one ring over the fold and out onto the ledge that Lowther thinks is a good idea. This means that you should pattern the Whizzer top first so that you can align the shelf pattern, as an offset to the top row of blocks, on the whizzer cone.

Alignment of the bottom two rows on the whizzer would be a nice touch and if I manage to do it, great. It will look better than not, but there will be zero sonic benefits or detriment. Alignment of the top cone and whizzer rows might actually be important sonically so I will enforce that.

Here is the link to the pics. Please resist editing the comments for the pics... I know it will be hard, but I will just become dispirited with my web ignorance and inability to lock my own intelligent comments in place for posterity.

http://picasaweb.google.com/hpurvine...85522118969202

Bud

[BudP]

Hi All,

Here are the, probably not very awaited, pdf files to allow you to print out the computer generated package for the Lowther DX4. Set your Acrobat for no page scaling and no auto rotate and centering.

One conic section has been added. It is to be used on the backside of the Whizzer, taped snuggly together, to provide a pen target guide to allow modestly correct patterns on the inside rows, on the main cone. It is called whizzer outside and is not to be used as anything but a pattern ring guide for that difficult to even see smallest ring set on the main cone. All puns and loosely moral interpretations are intended.

Have fun,
Bud

[BudP]

Well, ultrakaz has done it again. Look closely at the center domes on the attached Yamaha speaker system. That is the mysterious center dome pattern, with center spot and droplet of PVA on top of the center spot, I have mentioned a few times in this thread.

Bas, John and all who are contemplating treating large cones with center domes, you want to copy this pattern at the joint of the cone and dome. Though, you can squeeze them down into three rows, with the center row of blocks right in the joint, for less of this tedious activity.

The center dome treatment is important also, very important, as it controls the spike of energy from the center dome and controls the evenness of the high frequency dispersion pattern. Note how few blocks are involved, this is the number that you need, between four and ten pairs in two rings, total. Bas, you will be able to remove the round felt pieces you have attached to your cone. This, added to what you have already done, will control the whole cone. Then add Mamboni to the back just for the sake of bliss.

Then look around, our friend Mamboni is also showing up around the edges of the cabinet. You guys are ging to have to hurry to catch up here......

Bud