The begginings of my Clairtone globes

[Douglas Ingram]

Time to start this thread!

I have it in mind to build a modern version of a Clairtone Project G. This will be a big job and will go on for awhile. But I'm going to start here and add to it as I go along.

Step one is to make the speakers. The Project G's speakers are Wharfedale Super 10's mounted on a panel which presents the driver at the forward portion of a 18" spun aluminum globe. The front half of the globe is made of two layers of perforated aluminum with silver set inside of a black, and slightly offset creating a shimmering effect.

In an earlier thread on this topic I received some advice which lead me to choose to use Alpair 12s as the drivers. I will be setting them into some of Dave's octagonal Mar-Ken12 boxes and mount those boxes into my globe. My drivers are currently mounted in a pair of Pensil series Studio Reference Monitors and I am enjoying them very much. Already the best speakers I ever owned.

Last week I drew up the boxes full to better enable me to build them without error.

I also drew up the globes. This will be the first challenge to fabricate. I made a solid male mold from which I will make another female mold. for the time being I will be making my globes of fiberglass, possibly with carbon fiber outer layers. I may one day have access to equipment capable of spinning aluminum, but for now I will use composites.

The photos show an original Project G, the interior of the original speaker, my mold discs of MDF, my mold rough shaped.

As time goes by I will post update.

Thanks for looking! I am excited to be working on this project.

[zman01]

Douglas,

Ambitious and cool project - will be following this thread!

-Zia

[DYNABLASTERTUNERS]

super! Could you give some tips & tricks of making this bowl?

[Douglas Ingram]

Originally Posted by DYNABLASTERTUNERS

super! Could you give some tips & tricks of making this bowl?

Yes I will, in the fullness of time. I'm still working on it, yesterday I got some epoxy/microballoon mix on as a base for fairing the surface. Last night I refined my ideas for final shaping that does not require giant tooling.

I need to get my photos done in a way as to tell the story, and then get the time to post them!

[Douglas Ingram]

The first step in making this hemispherical mold was to draw it up in profile. It seems that a lot of people feel obliged to draw in CAD or Sketch Up, but good or pencil and paper, or in this case pencil and MDF, works just fine.

I start with the base line and the perpindicular center. Then I draw parallel lines to the base line set at the material thickness of my mold making materials. In this case it is MDF and I think that it measured out to 20mm. I had to do this twice as the first time I just made the assumption that it was 3/4". Easy to do and it makes a difference later.

Over these lines the maximum circumference is drawn. This determines the circumference (and diameter) and edge bevel, of each layer.

I cut out some of the interior of each disc to minimize the weight for handling purposes, while still leaving it solid enough to be, well, solid.

I drilled a hole at the center of each disc to keep them all aligned while gluing up the stack.

Having a lot of the excess already consistently removed by cutting the bevel greatly facilitated the next step of rounding it all over, both in terms of speed and consistent shaping.

Once the shape was as round as I could get it, I applied epoxy to saturate the MDF and then faired in the seams with an epoxy/microballoon mix. The next step will be to fair the mold into a perfect hemispherical shape as it still has small imperfections.

[andb]

Douglas, are your plans to rely completely on the A12's as FR, or do you plan to use the large box area (if you want to really make it look like a Clairtone) as a sub? Dave can correct me if I'm wrong, but it seems that one of the primary design goals of the Mar-Ken boxes is low frequency response. Given that you can make the large box area (for sub) handle this, it seems like that major design goal might not apply to your project... Further by not trying to take the Alpairs that deep by letting a sub take over, you relieve them from that extra effort.

How will the relatively wide front of the Mar-Ken mate to the globe and what will you use to round off the front? Could a simple ported or sealed enclosure better fit the fact that you need to get them into the globes with minimal impact on the front side, if you would have bass duty handled by another driver? Would it be reasonable to make a spherical sealed enclosure, with enough asymmetry on the interior to reduce standing waves of the same wavelength? It might not be too hard to make something using the Mar-Ken concept using a CNC machine that would end up being a sphere on the outside, even. Then you could simply cover them with the fiberglass or carbon fiber, which would eliminate the challenge of supporting the weight of the "box" in the globe and be great for reducing baffle diffraction.

I'm quite sure that your design concept will sound great as it is. Given the work you'll put in, I thought it might be interesting to throw out a few ideas that crossed my mind.

The Clairtone is really beautiful and iconic, I'll definitely follow your build with curiosity!

[planet10]

Originally Posted by andb

Dave can correct me if I'm wrong, but it seems that one of the primary design goals of the Mar-Ken boxes is low frequency response.

Actually the goal with all the miniOnken is bass finese. These are designed to a specific kind of rersponse curve in my modeler. This curve is not the actual response as the box Q is lowered by the high resistance of the slot vents. So in the end the bass goes down as far as it goes, i don't try to push it. A10 & EL70 are capable of the lowest response, and it is not a sin to add helper woofers.

Doug's Mar-Ken12 is a special variation that is a regular octagon from the front. It may still need some bevels on the back corners to make it fit into an 18" sphere...



One of the perks of buying a plan-set subscription is that i will do variations to meet special needs. Somewhere in the queue is a real scary one from a construction point of view -- a tapered 20 sided dMar-Ken7.

dave

[Godzilla]

LOVE the octagon!

[tade]

That "shimmering" effect is calle moire. I love it!

[Douglas Ingram]

I don't plan on using a sub woofer, at least any time soon, for a few reasons.

-I am very satisfied with the bass performance of my A12's in their present cabs.
-I have ENOUGH to do with just getting this Project G built (G for globe...)
-There will be a turntable in the console and I don't want to add interference to it. I actually have a Garrard Lab 80 for this, same unit as original. How cool is that? I have no idea how much actual use I will put it to, but it will certainly add to the end result.

I'm setting my console up as a full media center which will store and play all my digital media-audio as well as video- and have internet connectivity for streaming audio not in my library and for Netflix, etc.

As much as I like the idea of tube amps, I'm going to have to choose something that will run cooler as it will be inside the console. Any suggestions as to what would work "best" with these speakers? I'm not worried about "THE BEST!", just the most appropriate given my circumstances and budget.

Dave's octagon version fits the globe well, at least on paper. I had thought of talking to him and making it a cylinder and bringing the face of the cab right up to the surface of the globe. That way the slots would follow the surface of the the sphere in a way that looks more proper than straight slots. This would be an issue if the front screens were off. I decided that that was more of a theoretical issue than a real one, so simpler execution won out.

Dave, when I drew out the cab full scale on paper and then drew out the circle, it appears that I have a lot more space left over than your drawing is showing. I am assuming that the units indicated are correct, but I'll double check. I still have a lot of final fairing of my globe mold before I start the cabinet.

The moire effect is very, very, cool. I'm not sure if I will be able to achieve that yet, but I will be working towards it. One thing that I DO have is some old Brazilian Rosewood veneer plywood for the cabinet. You just cannot buy that now!