A Silbury Build

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#125
planet10 said:
making the whole tging look more like a teardrop the better.
Click to expand...

So we could add a 3D printed plastic "old-car lights" shape around the speaker:

vintage-car-side-light[1].jpg
 
#127
I've just got the 18 mm pre-cutted rectangles of wood.
45° cuts still to be done, speakers' cuts to be done, big round rear cuts to be done as well.

Everything has been done in birch plywood, except two internal panels that has been done in poplar plywood, because they would not fit in two sheets of birch, and building them with the same material would mean to pay a third sheet of birch, that nowadays is around 180 € (more than 45 €/m2). In poplar they charged me only 15 euros more.
I couldn't say no. Any downside on this choice?

I will need the help of a friend of mine to cut and glue everything, and your support to understand how to draw the big curve on the four side panels, plus the speakers' holes in the front panels. I will also need to buy the needed to dampen the internal part, both for the Silbury and the FHXL.

Is there a preferred glue?

Thanks
 
#128
I'm planning to use Saratoga W.D4.

To calculate the sagitta of the arc, I'd use the formula: s= r - sqrt(r^2 - (c^2)/4)
That should be 127 mm considering that the curve seems to start only after the 18mm of top and bottom.

Using the MA10.3 the front baffle will need:
  • a hole-through with a diameter of 137 mm;
  • a frontal annular cut with a diameter of 165 mm and a depth of 10.5 mm;
  • a rear chamfer at 45° (except around the 6 holes to fix the speaker);
  • chamfer at 45° and 50 mm on the two sides of the speaker.
As liner/damper for the surface of the area behind the speaker I plan to use 1/2" (12 mm) F-15 SAE Wool Felt, with a low density of around 2,3 kg/m2.

Please confirm I'm right, so I can go on with the work.
 
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#129
argoncat said:
Completing the glue up was relatively straightforward as was lining the diver chamber with 1/2" felt.. I put a 45-degree chamfer on the front baffle (given the 38mm thickness I used a 2" chamfer bit which is a little nerve racking).
Click to expand...
Hi, how deep have you chamfered the front sides? Is there an optimum considering 18mm plywood?
I would say the same front-baffle chamfer will be suggested for FHXL as well.

Thanks!
 
#136
I'm afraid I don't know what Blanda/Gronsaker speakers are, so I can't help on that particular front. The required lagging for FHXL is shown in the planset, but in effect you're lining opposing faces in the first expansion stage below the driver and around the upper fold. Silbury's chamber is lagged, more may be added at user discretion in the final manifold (expansion stage) dependng on what is preferred at their intended position; to a point this depends on the exact material used too as some adjustment may be required.
 
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#137
Thanks again, I will buy some more than what shown on the plans.
How can I decide that Silbury could need some more lining on the expansion or not?

The Blanda Gronsaker is off topic on this thread, but is a speaker David designed for me after I went to the Ikea and saw how nicely these two 280 mm bowls fit tigether:

1673886167353.png
 
#138
Fair enough; I can't realy comment on that as it's not my design & it's not my place to do so even if I had the full details.

Re Silbury (or anything else for that matter), essentially by trying them and deciding whether you want to damp the output or not. Room acoustics being what they are, this is not overly predictable in advance as construction, furnishings, amplifier, position of speakers & listener etc. within that all play a role. Nothing's immune from that (especially those speakers that are sometimes claimed to be immune from it 😉 ), it's just that people are often loath to make changes. Don't be afraid to do so, or use different levels on different channels if necessary due to asymmetric positioning etc.
 
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