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Old 1st December 2012, 11:11 PM   #211
xrk971 is offline xrk971  United States
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Door skins huh? Is that something one can get at Lowes or HD? The door skins if thin and flexible might also be used for the channel walls. I have also seen what looks like Balsa at Michael's that could work. You can steam the wood to soften it before gluing, it would look very old style craftsmanship like and maybe resemble a violin body....

Last edited by xrk971; 1st December 2012 at 11:14 PM.
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Old 1st December 2012, 11:18 PM   #212
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yeah most doors in houses in the US have thin luan ( a very soft wood) faces with corrugated cardboard stiffeners between them. Wood around the perimeter of course. In fact "doorskins" which are just the wood face are very cheap and might be perfect for the fronts and backs of the speakers.

MJL based calcs would be interesting..
I have wanted to model this but not sure how to deal with the bifurcation into two different lengths, the rest is straightforward to input into MJK's model. I suppose one can model two separate lengths and solution would be superposition of both? Is MJK still reading these forums?
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Old 1st December 2012, 11:25 PM   #213
Variac is offline Variac  United States
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It is similar to balsa, but not quite as soft, and looks OK stained and with a clear finish. Builders use it to fix damaged doors. But it would require some trickery such as steam or soaking to bend-that could be a nightmare! In fact now that I think about it, its probably 2 ply.. Would probably work for the final flare that is visible from the side. Based on the doors, bent corrugated cardboard could be stiffer than foamcore, and wouldn't require cutting to bend, just roll it up to break it down so it curves, then glue..


I've built a couple of BIB designs and they often don't work well at all if you swap in a different driver than they were designed for- even if the driver is the same diameter. That's why I think calcs for this speaker might really help things along- especially the size of the chamber behind the driver?

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Old 1st December 2012, 11:54 PM   #214
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As to the two lengths of the horns I suppose one could try experiments. Run each length and superimpose, and run a length that's the average of the two, with the combined sectional area, and see if there's a difference? I don't know..seems like the second sounds right intuitively.

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Old 1st December 2012, 11:58 PM   #215
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but twice as thick which is 4x or 8x as stiff- you engineers will tell me.
Stiffness goes up with the cube, so 8x.

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Old 1st December 2012, 11:59 PM   #216
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that's what I thought but it seemed too good to be true!
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Old 2nd December 2012, 12:34 AM   #217
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by Variac View Post
It is similar to balsa, but not quite as soft, and looks OK stained and with a clear finish. Builders use it to fix damaged doors. But it would require some trickery such as steam or soaking to bend-that could be a nightmare! In fact now that I think about it, its probably 2 ply.. Would probably work for the final flare that is visible from the side. Based on the doors, bent corrugated cardboard could be stiffer than foamcore, and wouldn't require cutting to bend, just roll it up to break it down so it curves, then glue..
The foam board is stiffer than broken down cardboard for curves as only the skin on the concave side is slightly scored. It bends wonderfully and easily as Cal will tell you if you haven't tried it yet. If you seal the scored skin with white glue after it is bent in place it will be even stronger.

WIthout modeling but scaling throat to match Sd seems to work well. I think this horn is so efficient it is forgiving to strict driver matching.
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Old 2nd December 2012, 12:42 AM   #218
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I have wanted to model this but not sure how to deal with the bifurcation
I would just create a single horn with all the bifurcation widths adding up to a total width.

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Old 2nd December 2012, 01:03 AM   #219
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I would just create a single horn with all the bifurcation widths adding up to a total width.

dave
What about different lengths of bifurcation?
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Old 2nd December 2012, 01:29 AM   #220
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The bifurcations make no difference... you have 4 sections of one length cascaded with 2 of another length. Because it is square and symmetrical bout the centre. You do have a slight discontinuity (The thickness of the spiral material) at the 1st birfircation

You can use a series of concentric circles intersecting with the centre line of a single spiral. The length of the spiral is your x axis, the circumference of the circle is the section (less the width of material crossed ie 2 or 4 material thicknesses).

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