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3D printed JVC Kaboom clone

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Hemisphere View Drop Down
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    Posted: 07 July 2017 at 10:28pm
So today I had an idea for a 3D printed clone of the JVC 'Kaboom!' Boombox.

2x Faital Pro 5FE100 in the standard Kaboom config (end to end in a ported cylinder enclosure[img], and 8x Sica 2,5 H 0.8 SL drivers arranged in pairs in all four corners of the cabinet. (two drivers side by side not ideal for HF, but the slim format of the drivers (66mm squared) really helps the form factor, they sound great and they're cheap enough. 

I call it a clone because it matches the Kaboom nearly identically in three ways: Dimensions (66.6x23.1x24cm), weight (7kg), and cost (about 250 quid). It'll blow it away in sound quality and output level, but you would need to add a chunky amp to unlock it's potential.

It may cost a little more than that. It would depend how cheap you can source the parts and services. And you would need to put it together, but it's designed to be a very novice friendly process.

(all diagrams are very preliminary - most of the details aren't illustrated at all) 

It's designed to use an experimental and not yet tested construction technique I've been thinking about, which is to 3D print the main body of a design as if it were an extruded profile, with parallel thin walls (1mm) using FDM (Fused Deposition M...odelling? M-something), with a cavity of 1cm between each. The cavity could then be filled with whatever the builder felt was the most suitable filler material.

The density of the filler is relatively unimportant to the strength of the walls, provided the surface layers are stiff enough. Ribs and bracing may also be printed into the model for extra rigidity. I'm hoping expanding polyurethane crack-filler type foam will do the job. It seems designed for this exact application. It might be a trick to evenly fill a 63cm long, 1cm wide cavity all the way through (but it can be filled from both ends, so only needs to penetrate 31.5cm each way), and the force of the expanding foam might not be appreciated by the walls if they're too delicate. There may be other filling options that work better, but that's the main candidate in mind at the moment.

The main reason to suggest this technique is to make the print job economically viable. The design uses approximately 950 cm3 of material. It's possible to find commercial FDM printers for as low as 6p per cm3, but 10p is more typical. So that's about 57-100 quid printing costs. If you were printing a 6mm solid wall that price would jump to 171-300 pounds, and you'd be adding 2kg to the weight of the enclosure.

It's still an option, if you wanted a less messy and more reliable build. A cylinder is strong enough that you might even get away with 4mm walls, provided you added sufficient bracing to the design.

At present I imagine all of the driver baffles being plywood, as well as a plywood strip on the top of the unit for simplicity of component mounting and reliability in repair/upgrade. Drilling and redrilling into plastic is bad enough in any case, let alone thin walled composite plastic.

It may be possible to adapt the design to be a 100% 3D print though. It would cost more to print but you could skip the plywood step altogether to balance out the cost.

The top of the unit is open, so you can mix and match electronics. It was designed to accomodate a Vibe Slick Stereo 4 I picked up on eBay for 25 quid. It's not the perfect amp for mobile applications, but for the price, it's great. 200w into 4ohms for the bass and 100w x2 in stereo @2ohms for the mid/highs. Such bargains appear on eBay all the time. 

The bass section is well and truly sealed in this design, isolated from the high end. Cables thread through the port under the grille and around to the amp. A shoulder strap affixed to each end a la Kaboom may be possible. Depends what off-the-shelf options exist.

Since the weight of the unit itself is so low, it can be justified to take along a bulky amp and a set of 3x 7ah batteries. That should run at max volume for close to 10 hours, which in this case is 117.5dB at 89Hz (113dB typical and 110dB at 67.5Hz).

One advantage of FDM 3D printing over typical plastic profile extrusion is that you can add more complex shapes, provided you're careful to watch overhang angles don't exceed 45 degrees, so I've used this to add four 'feet' to the enclosure, as bulbous protrusions that curve in and out again. Probably the most fiddly part to model.

Edit: An interesting look inside an actual Kaboom, for reference. 



Edited by Hemisphere - 08 July 2017 at 11:45am
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Hemisphere View Drop Down
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Joined: 21 April 2008
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hemisphere Quote  Post ReplyReply Direct Link To This Post Posted: 08 July 2017 at 9:03pm

This is the configuration I'm thinking about, not because it's optimal but because I have that amp, those speakers and those batteries looking for a purpose.

Optimally you would use smaller chip amps, smaller batteries, and less/lighter drivers. You could construct a neat electronics compartment which finished the cylinder with a sheet of metal or thin ply bent over a frame and slotted in/bolted in place on the top.

If you selected drivers more carefully/optimally, and used the 500g BassFace 4.2 amp with 400w RMS and crossover (currently 48 quid on Amazon) you could get the enclosure weight down to 4kg. A lithium battery pack could yield a practical system of 5kg with an output of 117dB and not inconsiderable bass extension. Limited battery life, not cheap to produce, and relying on an uncomfortable amount of 'what ifs' at this stage, but it's always a tradeoff.

The other advantage of 3D printing the enclosure of course is you have the skills to do it, you could modify the shape of the cabinet in all sorts of crazy ways without affecting performance. Teardrop, flower shape, hexagon, something a bit sci-fi like the original Kaboom, or just an asymmetric blob of some sort.


Edited by Hemisphere - 08 July 2017 at 9:33pm
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