What changes should I make to this cabinet?

[quickshift]

Hello

I hope you don't mind but I wanted to ask what changes I should make to this cabinet.

It'll be made from 25mm MDF for the most part, the front will be 3 layers of 25mm MDF which will be CNC'd and bonded together.

I have decided to try using 1 inch cylindrical wood for the bracing which I'll drill a hole through the center of and use a piece of threaded steel which will pass right through the whole cabinet. The nuts will be countersunk into the cabinet and filled over.

I also want to use steel rods to attach the woofer to the cabinet on 4 of the 6 fixing points.

An idea for coating the internal surfaces is to use a layer of polystyrene beads (beanbag filling) about 10mm thick which I'll either mix with latex sealing paint and paint on or just glue on. It depends how the beads behave as to which method works best.

I'll use bitumen backed foam for the mid enclosure and the tweeter will be sealed into the front baffle.

What do you think?

[quickshift]

Pic 2

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Pic 3

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Would you believe....... pic 4

[quickshift]

Oh, also, this is a close up of the profiled bit. I don't know if this will work well or not but it looks nice IMO

Ignore the bump at the top, I have only been using 3DS for a couple of days and I'm not very good with it yet.

I'll smooth the top bit off IRL.

[wintermute]

Personally I'd make the mid cabinet deeper rather than tall and shallow, should help reduce reflections back through the cone. Try and use the golden ratio for it, if you can do so without too much difficulty and make the longest dimention the depth.

Also with 75mm thick baffle, you will need to flare the cutouts for the drivers (on the inside) so that the drivers can "breathe"

Tony.

[quickshift]

Thank you for your advice.

It shouldn't be too difficult to alter the ratio of the cabinet <<reaches for calculator>> and flaring the cutouts will be easy enough.

[soongsc]

Originally posted by quickshift
Thank you for your advice.

It shouldn't be too difficult to alter the ratio of the cabinet <<reaches for calculator>> and flaring the cutouts will be easy enough.

Maybe considering the Golden Ratio might help keep internal resonances to minimum.

If the baffle is built up of multiple layers of MDF, you might want to see how each layer is cut out. If you do it layer by layer, you need some alignment holes to keep them in place when doing assembly. Also each layer will have a different bit, it's going to be a little tricky. If you CNC it after the layes are combined, you might actually need a round headed bit to carve the edges out, lots of machines hours. $$$ You could also rough cut each layer first, combine them, then carve the edges. The tricky part seems to be where the concaved edges turn into round edges.

The way Thiel does the edges makes it easier to manufacture.

[quickshift]

Yes, good point, thank you. I'm adding alligning holes to the final version so I can use dowels to make sure the layers are alligned properly when I bond them. I'm planning to use my car as a weight when I'm bonding the layers - I'll jack a wheel up and lower it down onto the baffle - that should be heavy enough. I'll pop up a couple of pictures of it in action.

The CNC people say they will need to use a ball cutter so it works out at about £150 per baffle. I thought about changing the design to the curves are less complicated but I like the design as it is and I want to try to make something I'm really proud of with no compromises.

[soongsc]

Originally posted by quickshift
Yes, good point, thank you. I'm adding alligning holes to the final version so I can use dowels to make sure the layers are alligned properly when I bond them. I'm planning to use my car as a weight when I'm bonding the layers - I'll jack a wheel up and lower it down onto the baffle - that should be heavy enough. I'll pop up a couple of pictures of it in action.

The CNC people say they will need to use a ball cutter so it works out at about ?50 per baffle. I thought about changing the design to the curves are less complicated but I like the design as it is and I want to try to make something I'm really proud of with no compromises.

If you use the ball cutter, you will get better results after glueing them together, this will iliminate the need for alignment dowel pins which adds additional work in the process. When you glue them tocether before CNC, you will only need guides on the sides.