The Caves of Arne Saknussemm (A Journey to the Bass of the Earth)

[D-MAN]

Gil, you painted the inside of the back chamber?

DM

[WMcD]

Oh sure I painted the back chamber. I used special acoustic paint. Smile.

It was satin black latex from Home Depot.

Gil

[D-MAN]

That is just too much!

Although if the back chamber was painted white, the drivers might think that it was a smaller volume, so indeed black was the better choice there! :^))

DM

[WMcD]

As far as tips for other builders, I dunno. There is potential for telling tales of woe, being self congradulatory, or over pedantic. But I'll carry on. Bear with me.

Back chamber sealing is always an issue. I used Titebond II for glue. It will fill a gap. There were not any gaps that I could see but it is better to be safe. I also sealed along the seams with RTV, and then painted.

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Painting all the interior, including the horn surfaces may be over the top. There is no 'thought police' inspecting the interior. Still when we take apart old plywood construction the stuff looks a bit oxidized and verging on degraded. Paint might help a little in the long run with mold and critter invasion.

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There is the issue of what to use to seal between the motor board and the surface it mates to. I used a string of Moretite. Same one the hatch covers. In a previous project, the Bigger Belles, I used the sheet rubber which HD sells to line tool drawers to make a big gasket seal the hatch cover. Unfortunately it adhered to the painted surfaces. I had to use the wire and loop handle type saw which is used to cut PVC to get it open. Cardboard might do as well as a gasket.

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Getting from small plans to actually fullscale is another issue. I obtained 48 inch wide graph paper and drew out a front and top elevation. The paper grid is not always true because it can shrink and expand in humidity. So I measured what I drew with a 24 inch rule which was divided into 100th of inches. I found that in an art shop in the Loop, now closed. The rule somehow got lost. Dang.

Metric rules are far more common and there is really no reason not to convert everything to metric at the start. HD, by the way, has one metric-English tape rule on the rack. Very handy. Fractions are a pain.

In any event, the full scale drawings allowed comparison of what I cut, with what I drew and a measurement of angles.

Of course now we have some plans by a kind gentleman here. I suppose if your draw it out, you only need to draw 1/4 th of the whole bass box because it is symetric in two axes.

If anyone wants some big graph paper let me know. I can send you a lenght.

====

The sequence of assembly is another issue. I followed that suggested by the SpeakerLab plans for the SK.

Put down the ramps and prisms first as the Professor showed. I then I positioned the base of the dog house on the ramps carefully, and drilled for the screws which would go into the ramps. Then I built up the doghouse. Then glued and screwed the doghouse to the ramps per the pre drilled holes.

The next step was to build the end plates with hatch. The photos show the hatch construction.

Here we get into accurate alignment of sub parts.

You have to position the end plates. Roy posted photos of how they do this at the factory. This pretty much like K-Horn construction. I was working with a Black and Decker stand to which I'd mounted a piece of MDF. Hope has more sturdy workbenches but it is all the same idea. You should build a good workbench like these. They establish the flat base of construction which is the front of the bass bin.

This is a general subject that you have to make tools to make the ultimate product. The workbench is one of them. You've seen some photos (above) of the saw guides. But you might like to make a tuning fork too.

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One problem is making a screw hole through the end plate and exactly into the middle of panels which make up the interior of the horn. I.e the doghouse at first, and then the intermediate divider of the horn in plan view. I did not quite trust my drawing to plot the exact positions. Being off a little would split the edge of the ply.

I made up what I call a tuning fork feeler. Sorry no photo. This device starts as a long piece of rectangular plywood about five inches wide. Then a slot it cut almost to the end. The slot is a little bit wider than the end plate. Therefore two tines of identical lenght are formed like a tuning fork in aspect. A very tall U.

You slide the fork into place along the end plate. The point of the bottom tine hits the doghouse edge or the edge of the intermediate panel. The top tine shows the same location on exterior of the top plate. You can then know the exact position of the underlying panel relative to the the hole you're trying to drill. Dang, I should have taken a photo. It is a handy tool.

===

I was offended by a comment in the SpeakerLab plans. It said that no flaw is so big that it can not be filled in with RTV. It sounds like an excuse for sloppy workmanship and patch up solutions.

I mellowed a bit. I experienced chip outs and some joints which were not quite up to CNC standards. My thougth is that we're trying to make a good bass horn with home grown carpentry, not a violin.

= = =

The good part about the Jubliee is that is much more buildable, or cutable, than the K-Horn. So if anyone wants to build the these ultimate corner horns, the J is the way to go.

Best,

Gil

[Guest " "]

Great collection of notes.

Agree on the metric approach, already have the us/metric tape measure you mention.

[WMcD]

I'm editing out what I'd posted last night in this spot.

People point out, correctly, that said some things about Picky and his post which were out of line.

Naturally, I think this is a wonderful place and there is no reason for ad hominum attacks which I slipped into out of anger.

Gil

[WMcD]

Metric is frendy to woodworking on this sort of project. We need all the help we can get. It is just a matter of moving to a new concept.

One millimeter is pretty much the tolerance I can cut with the saw, at best.

You really owe it to yourself to start working with the metric tape measure from HD and see how the rest of the world works. Only crazy Americans deal with 32nds.

Gil

[colterphoto1]

"You can see where this is going. When good Michael says, just take them outside, it pushes a hot button. Sorry, again."

No to the photo comment..., actually Gil, I'm trying to gentle down my image a bit. I reread the past few pages this am and wanted to say I'm sorry for the 'outdoor' comment. I was trying to help you in your test quandry. Didn't realize there was a hornet's nest in one of those ports.

You did a fine job on the build. I like the white color. Good job. Carry on.

But I do miss our avid adventurers- it was a fun couple of weeks there. Thanks.

Michael

[Xover]

Hear hear on the sexually oriented postings Gil. I don't understand why someone would drag that kind of stuff into a loudspeaker forum.

Something else that annoys me is the group of folks that exhibit behaviors behind the cloak of anonymity the forum provides that they would never show in an open enviornment.

Nuf said, Good work Gil and thanks for the entertaining delivery.

[filmboydoug]

.

[colterphoto1]

The veneer is not quite up to spec and I'll work on it in walnut. The

grills will get some black paint before the cloth is applied. I'm

undecided about how to hold everything in place. Velco seems easy but

cheesy. Magnets?

magnets are indeed what Klipsch is using on the new Cornwall III's. I don't know how you'd get them positioned accurately unless maybe you attached the double magnet assembly to say the motor board, than put dollop of glue on the grille side, then carefully lowered the grille into place, letting cement or whatever cure throughly.

I was just working with some of the CWIII's and in addtion to about 6 magnets, there are several small clear 'bumpon' pads like I use on the backs of picture frames, possibly to act as addtional spacers and keep the grille from rattleing (think clear plastic 3/8" dia footies)

Michael

[WMcD]

Oh, Michael, Michael, Michael.

Don't worry. As I said, the comment hit a hot button, from the old days. Also, I'm living in a rather conservative condo. For example, they allow two dogs per owner, but they have to be under 30 pounds. The president of the condo board was talking about getting a scale to weigh them.

So I don't know what anyone would think of outdoor speaker testing on the premises. Probably half the people would 'Vetch and the other half would want to help. Another hot button. They're all good people. But I don't want to make enemies.

I'm a bit sheepish about the photo quality. I expect you relish working with your Hasselblads. Someday you'll have to let me play with them.

I never got to that level of hardware. But I loved my F3. Available light was my nitch. The fast 102 mm lense was the best! I still have the collection. But the Mavica is of course necessary for present day recording and posting.

The Mavica has exposure adjustment, flash override, and some fixed focus settings, including macro. The photos of The Professor turned out pretty well.

On the other hand, I do miss real exposure information and manual focus.

I have the Sony strobe. It helps a good bit. I also have a Metz 45CT-5 potato masher strobe and a slave trigger. The plan is to see if the Mavica exposure system can be played with so the extra light from the Metz works out.

I'm not quite sure why the photos of the corner horns are so fuzzy. The best guess is that despite the use of the on camera stobe, the image is recorded over a long period. So there is camera shake. I have to get out the tripod.

BTW, I learned with the F3 what all the experts say. Using a tripod converts ordinary film to ultra sharp. I did one set of photos for a case. A ski lift cabin inside the lift house with only one high window for light. Very dark. 40 second exposure at F22. Depth of field was big issue.

I dropped off the roll at a one-hour shop at a Walmart type place which could do 8x10. A remarkable find in upstate New York 15 years ago.

I really was praying for the best and expecting the worse. Fortunately the young fellow running the shop there was very intelligent. Maybe I read in too much and the developing machines are as much point and shoot as a modern camera. No operator control. But is nice to find that you've put your baby in good hands.

In any event, the results were eye-popping. People looking at the prints always say, Holy Crow, what film were you using, some professional stuff you keep in the refrigerator?

Nope. I tell them the image quality is in the tripod (of course necessary in that project). I'm not sure they believe it.

Again, don't worrry about any comments by you and whether they are offensive. We all know you've got a heart of gold.

Best,

Gil

[WMcD]

Okay, I read the several responses.

I should not have attacked Picky that way and people are correct to point it out.

Picky, please accept my apology.

I have removed my angry post about Picky's post.

It is time for me to get back to speaker testing. That is what we're all here for. Time for me to mind my own knitting and not get sidetracked.

Gil

[freddyi]

Ulrathip - btw, why was that cave symmetrically bifurcated instead of meandering snail-style coil?

[jt1stcav]

Regardless to the various SNAFUs and FUBARs concerning various posts (that I've obviously missed having just read this thread in its entirety), Gil's presentation has to be applauded for his creativity and imagination while building Jubilee bass bins, and I do hope it continues in some fashion (plus I hafta know if Gretchen ends up with Hans, Alex, or G.I. Joe)!

I'm not a DIYer, but I still find these threads interesting reads, and I wish Gil the best in finishing this project.

Thanks for the laugh, too.[]

[WMcD]

The Professor and Gretchen spent Sunday on the project.

The grills have been painted with two coats of satin black latex. (Shhh, it has special acoutic properties. Smile.) A mini roller really helped. (Just the correct size for action figures.) The idea is to have no shine though when the black grill cloth is in place.

They also used an iron to remove the mahogany veneer. This also gives some idea of how any such units might look with a light color veneer. You'll have to imagine cane grill cloth. It would be classy if anyone wants to go that way.

Photography worked out better with a couple of spotlights. The camera seems to autofocus properly. Preset focus with flash is not working nearly as well.

No work on attaching the panels. The front panel is being supported by an RS sound meter in its case. The Professor is thinking about the best way to use magnets.

Gil

[WMcD]

To answer Freddi's question.

There is the problem of getting the signal to go around a corner. I've read many explanations of the problems and solutions.

We have to first realize that the energy is alternating between particle velocity (so we need reflectors) and pressure (so we need a fairly uniform pipe area without discontinuity).

Then there is the theory that there is drag at the confining surfaces. And maybe things will take care of themselves with a gentle bend.

The most easy to understand theory is that we want a curve with a sharp bend. Small radius. Consider this like a human runner on a track or a car on an oval track. The guy which is forced to run outside has to cover more distance. In the wave-world, that means he arrives late. Ariving late is a phase problem.

The wave on the outside track arrives 180 degrees late, and cancels out the the inside runner. That would be bad.

What to do?

If the path can be divided into two paths, each are more narrow. Importantly, the bend is more narrow. The result is a more narrow path and "going around the outside" results in a smaller path distance difference. (Ahem, aliteration.)

There is something to the thought that a big tuba-like path gets around the problem. More gentle curve. Maybe the pressure and particle velocity, and drag, all even out.

If you look back at the opening frame of The Caves (posted April 1st), The Professor is looking at an illustration from an ancient text. It is from Jean Hiraga's, "Les Haut Parleurs".

Jean included on that page some historical horns, (1) a gently curved bass horn built into a ceiling window light. Those are not action figures; these are big structures. He also shows (2) a tuba -like curled horn, probably an WE unit. Then, The Professor is showing (3) the Jubilee cross section. You can compare the relative merits of the geometries

This opening was a little joke of mine. I had no conscious idea at the time that it addressed the issues you present in a compact form.

Gil

[sunnysal]

we want to hear about listening tests and in room measurements! get the doc and the rest of the crew roused and to work! tony

[JohnA]

Gil,

How cool!

Initially, I read the first few threads and misunderstood what you were

doing. Now, I see you've built Jubilees! What are you doing for the HF?

Have you looked at a Radian 850PB? It's a 2", but looks to have

excellent response.

[PrestonTom]

I have been re-reading this thread and thorougly enjoying it. Gil if you are still in the mood I, among others, did have some questions.

For instance :

What was the reasoning behind using the dual 15 in drivers rather than the 12 in drivers from the jubilee plans?

Could you give us some of the targeted parameters (volume, flare, mouth) etc that you were shooting for and which ones did you have to compromise on?

What do you imagine the pass band is on the cabinets (esp the usable upper frequency limit)? Perhaps you have had a chance to do some physical measures (although I appreciate that these are neither trivial nor logistically simple)

As John mentioned, what are you planning regarding the HF section?

I realize the format you choose for the thread is a labor-intensive one; however, it is a delight to read. It is also inspiring...

Thanks,

-Tom