Phase plug shape

[SeisTres]

I found this quite a bit ago on some thread; hope it helps.
http://www.centauriaudio.com.au/diy/plugs.html

[WB]

Ideally, yes.

[Monomer]

I'll make the plugs.

if someone tells me what the proper shape is. I'm a tool and die maker, not an acoustical engineer.

A mirror image of the center of the actual driver.

The mirror image would extend all the way out to the surround I would think?

Need to know the offset, like the one-way max excursion.

what about the plugs shape upfront? most have a bullet like shape....

[Bill Fitzmaurice]

what about the plugs shape upfront? most have a bullet like shape....

I measured response with and without that addition and in these cabs it doesn't work as well with it.

[Monomer]

what about the plugs shape upfront? most have a bullet like shape....

I measured response with and without that addition and in these cabs it doesn't work as well with it.

Good to know.

[Tim A]

A couple of things. It took time and a lot of trial and error to produce the fillers. There are a ton of foam products on the market, but only one that works well. The forms have to be made so as to provide a method to get the product out in one piece. That has to do as much with the shape and material as it does a good release agent. It also has a lot to do with accessing the product while it's in the form. If you can't get it off without damaging the product, it's worthless. You also have to be able to produce them in multiples. When the fillers were at their peak it was difficult to keep up, and I can make as many as 14 full sets at one time. In order to produce them you need a year-round dedicated work space where you can leave everything set up and ready to go. It is a constant process. Fill, cure, release, fill, cure, release.

Ultimately, it's no where near as easy as it sounds. I had the same frame of mind when I started doing fillers, I figured it'd be a pretty simple proposition. It took a considerable amount of sweat equity, money, and all the other stuff that goes into R&D to be able to supply enough to Leland to make it worthwhile, and even at that we fell behind from time to time.

By comparison, the phase plugs are a smaller product that will be more difficult to produce. I can't (won't) explain that, it'd give away too many of the nuances I learned during R&D, information that I consider to be proprietary.

[WB]

Need to know the offset, like the one-way max excursion.

1/2".


I'll be starting a Jack 10 or 12 shortly and this discussion has given me some ideas. I'll be making only one, so I'm willing to spend a little extra time in making just one. This is what I'm thinking:

- use Saran wrap instead of regular plastic.
- line the driver face with it.
- make several round wooden 1/2" ply discs of the appropriate diameters to make a large plug to completely fill in the driver cavity, with the largest diameter disc flush with the frames gasket, and the smallest one touching the dust cap. These are glued together when the right sizes are determined.
- make the baffle with the proper phase plug cutout.
- attach the large plug to the baffle.
- fill the remaining spaces between the large plug and driver with expanding foam.
- when cured, separate the driver and disc.
- using a router with a tall 1/2 bit, plunge out the four openings, using a pattern following attachment against the baffle.

The only thing I'm not sure about is how much force the expanding foam might push against the surround, if any.

[gilscales]

Need to know the offset, like the one-way max excursion.

1/2".


I'll be starting a Jack 10 or 12 shortly and this discussion has given me some ideas. I'll be making only one, so I'm willing to spend a little extra time in making just one. This is what I'm thinking:

- use Saran wrap instead of regular plastic.
- line the driver face with it.
- make several round wooden 1/2" ply discs of the appropriate diameters to make a large plug to completely fill in the driver cavity, with the largest diameter disc flush with the frames gasket, and the smallest one touching the dust cap. These are glued together when the right sizes are determined.
- make the baffle with the proper phase plug cutout.
- attach the large plug to the baffle.
- fill the remaining spaces between the large plug and driver with expanding foam.
- when cured, separate the driver and disc.
- using a router with a tall 1/2 bit, plunge out the four openings, using a pattern following attachment against the baffle.

The only thing I'm not sure about is how much force the expanding foam might push against the surround, if any.

I have used a lot of expanding foam in my time as a contractor and there are several types, from minimum to triple expansion, the only problem i see with that is using the right amount of foam to fill in but not deform the cone/dustcap area, this is why i thought that a complete foam plug weighted by a small pc. of ply to allow the foam to expand upward aginst the ply after the cone area was filled in by the expansion.

If you had a problem with the plastic/saran wrap sticking to the foam you could first spray it with olive oil or pam, unless it stuck to the foam very well then it would make a nice skin to protect the foam from flaking in the future?

After the plug dries you could slice it from the side with a large bread knife to the desired thickness, glue it to the baffle and then just cut out the four areas with the same bread knife.

dont know if it would work, just a thought?

[gilscales]

Here is another idea for a phase plug material, http://www.schundler.com/mixdesigns.htm

this site explains how to make lightweight self leveling concrete.

if made to the lowest density (formula using cement and perlite only at 1 to 8 ratio) this would be very lightweight and with the driver cone covered in a protective plastic, could be poured into the driver within a 1/2" or 5/8" from the top edge of the frame.

once cured the plug would be the right size and could be glued to the baffle and trimmed with a bread knife as this formula would not be to heavy or dense to cut this way.

[BrentEvans]

There are methods that could give a better result. The method in the plans is one that the average builder can use. If one wants to try something else, well, that's what DIY stands for.

Sigged.

Oh, the irony.

[Bill Fitzmaurice]

There are methods that could give a better result. The method in the plans is one that the average builder can use. If one wants to try something else, well, that's what DIY stands for.

Sigged.

Oh, the irony.

I didn't say that trying something else would necessarily be worthwhile. When it comes to alterations to my designs there is a criteria required to gain my approval: That the result works. More than a little bit of effort goes into these cabs, and as witnessed by the constant stream of updates I don't consider anything perfect. If there's a better way it makes its way into the plans. But if it's not an improvement I don't endorse it, and if it's not worth doing at all I will say so.

[Monomer]

A couple of things. It took time and a lot of trial and error to produce the fillers. There are a ton of foam products on the market, but only one that works well. The forms have to be made so as to provide a method to get the product out in one piece. That has to do as much with the shape and material as it does a good release agent. It also has a lot to do with accessing the product while it's in the form. If you can't get it off without damaging the product, it's worthless. You also have to be able to produce them in multiples. When the fillers were at their peak it was difficult to keep up, and I can make as many as 14 full sets at one time. In order to produce them you need a year-round dedicated work space where you can leave everything set up and ready to go. It is a constant process. Fill, cure, release, fill, cure, release.

Ultimately, it's no where near as easy as it sounds. I had the same frame of mind when I started doing fillers, I figured it'd be a pretty simple proposition. It took a considerable amount of sweat equity, money, and all the other stuff that goes into R&D to be able to supply enough to Leland to make it worthwhile, and even at that we fell behind from time to time.

By comparison, the phase plugs are a smaller product that will be more difficult to produce. I can't (won't) explain that, it'd give away too many of the nuances I learned during R&D, information that I consider to be proprietary.

Tim,

I know the difficulties of making such an item. I appreciate the concern. I do have a lot of free time and space needed.


Now, does it have to be foam?

[Philip Kelley]

I can suggest another way to make an accurate mold of a speaker cone, one that I've used to make molds for fine art glass casting. Alginate is a material that is used extensively in craft and medical applications. Think dental impressions. It's inexpensive, readily available, easy to work with, 100% non toxic, and has great release properties.

In practice you'd drape the face of the speaker with plastic film (saran wrap) mix up your alginate, pour it in, and pop our a perfect impression in no time. From that, it's easy to make a plaster mould which could be used to cast a number of phase plugs- perhaps out of of one of the expanding foam or lightweight concrete products referenced above.

You'd need to make sure that the weight of the alginate would be supported by the speaker without undue distortion while making the initial impression. The alginate is somewhere around the same density as water (and easily measured,) so that would give a good idea of how much pressure is going to be exerted. I have little knowledge of how stiff or delicate speaker cones are, so I'll leave the conclusion to more informed folks on this board.

Fun to consider, and I may play with a fancified phase plug in my upcoming 2 x J10 build, more because I can than because it will make a huge difference. Indulge me if you wish; why not just make some accurate measurements of the speaker cone and machine something to those specs? I'm thinking EPS foam (insulation board) would do the trick nicely and it machines like butter. Plus it weighs next to nothin'. I'd probably give it a painted finish for a harder reflective surface.

[Monomer]

Still in the works.


Molds have been popped, cones destroyed.


And I've had a lot of fun





The pattern/mold supply down the street seems to HAVE EVERYTHING. It's a great place to EMPTY YOUR WALLET.

[Greg Plouvier]

Sort of relevant:

http://www.centauriaudio.com.au/diy/plugs.html