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Old 13th July 2003, 11:28 PM   #1
WVL is offline WVL  Netherlands
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Lightbulb Pipe speaker with a twist

I'm fairly new at this, which is why I'd like to ask your opinions about my own little project.

I'm about to make a pipe-speaker, a speaker with a cilindrical-shaped inside. Most I've seen so far are based on sewage-pipes or something similar. I want to make one with a twist.

This is what I have in mind. Click the image to open in full size. (please do not mind the quality of the picture, I'm not using CAD programs, this is made in Maple V (a mathematical software package)

I want to make it using stacked pieces of wood, like such :
Click the image to open in full size.

I've been thinking on how to proceed to make the whole speaker, I hope it's possible..

first I want to cut out all the single layers, and drill in the center hole, as well as the little hole (the little hole is in a different position for each layer, it will help me to get the right 'twist')

next I want to use a sewage pipe and a thin metal rod to put the pieces on. I will use the sewage pipe (the layers will fit around tightly) to center all the layers, and the small rod (fitting the small holes) to get the right 'twist'.. then all will be glued and pressed together.

My questions :

what do you guys think would be the best material? I've been looking around and 4mm MDF looks to be the best option. (thinner is better, as the result will be much smoother, so I don't have to sand like crazy..) I can get different materials, but they don't look right for building speakers.. any ideas?

Does anyone have experience with glueing that many stacks together? how much will one layer of glue add to the height? The height I'm aiming for now is about 100cm (not including feet). Which will position the tweeter at just about ear-height. (sitting in my chair)

Will the shape distort the sound too much? the one shown here is meant to be the left, I want to twist the right speaker in the other direction.. the idea is that the sound going downwards is reflected towards the listener.. (or is it a better idea to reflect it _away_ from the listener?!)

What about finishing? I'd really like veneer finishing, but I don't think it's possible to apply that to this shape? Any experiences?

Would it maybe be better to bend wood, rather than to stack? bending in this shape seems fairly impossible to me.

let me hear what you guys think. All suggestions are welcome.

(btw, this will be the first speakers I'll ever build, but I don't want to make some box-shaped ones to try stuff out.. it will not give me experience in making shapes like this )
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Old 14th July 2003, 12:02 PM   #2
Vikash is offline Vikash  United Kingdom
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Quote:
Will the shape distort the sound too much?
I'm no expert, but I think the consensus is on having minimal parallell walls on the inside to disperse the sound and thus reduce standing waves, and no sharp edges on the outside around the driver, especially equally distanced - to reduce diffraction effects (it's not clear where you'll be placing the drivers). Seems like your twisted design has some inherent advantages.

Good to see such an adventurous design. Let us know how you go about achieving it.
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Old 14th July 2003, 12:19 PM   #3
7V is offline 7V  United Kingdom
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Your speaker looks interesting. Can you tell us what sort of bass-loading principle you are going for (1/4 wave, transmission line, sealed box, ported) and if you have decided on the drive units?

Generally, it's easier to cut out the external shape as well as the internal. This would mean less sanding and would enable you to use thicker segments. The whole thing wouldn't take as long to build.

Andy Graddon is compiling an excellent resource for curved speaker construction and this may be helpful.

PS: I think that veneering will be tricky (at least)
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Old 14th July 2003, 12:56 PM   #4
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I like the design, a work of art to be sure. An ambitious woodworking project however, and to effectively create good art, one must show control of the medium, and the outside finish will be difficult. Especially in wood.

Veneering the curved surfaces won't be doable with full sheets, as wood isn't flexible enough to bend in two directions at the same time, you would have to carefully join many strips of veneer.

Have I got this right? You want to stack 4mm pieces to a height of 100cm? Isn't that 250 pieces of MDF?

Perhaps an easier way of getting your spiral shape might be to sandwich one or two inch (25 or 50mm) foam boards between the MDF ones, these would be easier to shape. Also, by alternating large and small inside holes you might be able to accomplish a v-shaped, down facing, interior treatment similar to 7V's Nonsuch design, utilizing the pipe for assembly allignment only.

As for the exterior treatment, I suggest plaster or auto body filler to give you a more workable finish.

I also hope you have as much success as Kneadle had with the design he couldn't build.
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Old 14th July 2003, 01:06 PM   #5
Vikash is offline Vikash  United Kingdom
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Quote:
I also hope you have as much success as Kneadle had with the design he couldn't build.
Don't you mean more...lol
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Old 14th July 2003, 01:17 PM   #6
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Hi Vikash- The design Kneadle couldn't build was a success.

And great fun for many watching, helping, and encouraging.
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Old 14th July 2003, 02:03 PM   #7
WVL is offline WVL  Netherlands
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@ 7V : I haven't quite decided yet. either it's going to be a closed box or vented. First I want to establish if this shape is going to work out at all, before I start picking out the drivers (I think I'd like a closed box best btw .. The speakers I have now (Energy e:XL-26's) are vented, and have somewhat too much bass (they boom too much).

Also, what do you mean, cut out the exterior? I don't have to do very much sanding if I use enough layers. All the pieces are square. Also I think it would be *very* difficult (for me atleast) to make the slabs thicker and saw the outside in the right spiral shape...

i already saw that page you mentioned Nice speakers!

@x.onasis : yes, that would be 250 layers. I don't like the idea with the different shaped holes to get a sawtooth, like the nonsuch speakers. That way I can't use my sewage pipe to position the slabs (btw, the pipe is only for constructing, will be removed when all the slabs are glued together.)

About driver placement : I wanted a normal placement with the tweeter above the woofer, like this :


Click the image to open in full size.

then again, maybe because the curve gets stronger downwards, it would be easier to put the woofer above the tweeter (the top is the most flat)
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Old 14th July 2003, 03:46 PM   #8
kneadle is offline kneadle  United States
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I was hoping someone remembered. Not that I'm averse to self-promotion, but still...

I'm watching this project with interest. I'd like to see some alternative techniques to bending and twisting speaker enclosures so that I can eventually borrow the best of these techniques for my next project.

Search "spiral" for the completed project.

Battle on! Much Success awaits thee!

Dave
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Old 14th July 2003, 09:20 PM   #9
7V is offline 7V  United Kingdom
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Quote:
Originally posted by WVL
Also, what do you mean, cut out the exterior?
Ignore me. I hadn't quite visualized the shape.

Good luck with this one. It will be fabulous if you can pull it off.
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Old 14th July 2003, 09:25 PM   #10
WVL is offline WVL  Netherlands
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I've been playing around with the positioning of the drivers. After all woofer above tweeter has the better looks. What else could I take into consideration when determining position for the drivers?

Positive stuff :

- woofer above tweeter looks better
- woofer is now in the flattest part, easier to fit
- tweeter is still at about ear height

Any negatives you can think of?

btw, I also modelled the right speaker. Still no-one having a clue about the thickness of 1 glue-layer? The more I think about this, the more I think I need to do a small test-speaker first, in the same shape, but maybe 1/2 of the twisting. Otherwise the curves would become too sharp. Does a test 10X10X10 cm speaker-block sound good enough?

What I'm worried about most is the finishing of the whole thing. Does anyone have pictures of finishing MDF? Either I want a glossy finish, or maybe a satin finish to it.. What I'm mostly worries about is that I'm going to loose sharpness on the edges. So edges will look more like :

|
\_

then like

|_



both speakers :

Click the image to open in full size.


(what do you think looks best? tweeter on top or the woofer?!)

btw, maybe you didn't notice, but the speaker gets thinner near the top, I think it looks best..
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