Introduction: Marble Boombox

I like to juggle with poi in the park with my friends, but we didn't have a boombox just a small bluetooth speaker from ebay, it was just a couple of dollars but it's always giving up after an hour. I wanted a cool boombox like jbl xtreme or B&O but those are really expensive for me.

So why not building?

So I designed this speaker to:

  • be portable
  • use bluetooth, sd card, etc.
  • really light (of course it's not marble, it's just an effect)
  • could use it for hours
  • look expensive
  • but cheap

I found in the garbage a fully functional 2.1 speaker, and I used it for this project.

I made the case for the boombox. So right now, this is just the tutorial about the case.

Sadly I'm still waiting for some of the inside parts, because ebay and dx is slow as a pregnant snail :(

I will upload the soldering later.

Step 1: Tools and Materials

Tools needed:

  • Dremel tool (with lots of sanding head)
  • Jigsaw
  • Drill with hole saw
  • Scissors and Knifes
  • small paint rollers (I made them, because it has to be really small)
  • Sandpaper (40, 80)
  • Brush
  • screwdriver and small screws
  • wood glue
  • hammer & small nails
  • soldering tool

Protection:

  • Rubber gloves
  • Goggles / safety glasses
  • Mylar foil / PET foil (I bought in a marijuana grow shop ) - 5$
  • Clothes for messy work - (do not wear your favorite H&M sweatshirt for this)

Materials:

  • Birch plywood (50cm*50cm) - it was free from the garbage
  • Corkwood (6mm 1m*60cm) - 4$
  • decorative fiberglass veil - 2$
  • fiberglass veil - 3$
  • Polyester resin (1kg POLIMAL-123-TP-ISO, without paraffin, for manual lamination, unsaturated) - 6$
  • Activator for the resin (Curox butanone peroxide m302, 100ml,) - 1$
  • White spray (I used radiator enamel paint, the resin dissolved it and made the resin become white) - 5$
  • Copper paint - 5$

Inside Parts:

Step 2: Case Design

Before doing anything I did an in-depth research about how to build a speaker. I'm still learning, therefore this is my first speaker, and I made a lot of mistakes and I even thought this is a failure sometimes. But I'm writing down everything so I (and probably you too) can learn from my mistakes. I made a lots of plans and calculations, how to make it cheaper, lighter, sturdier, etc. So I'm going to share my mistakes and my advises.

First is inside:

The case is protection and insulation, but I need electronics to protect. So the first thing is to make the schematics and plan every part. And buy them, and test them without the case. The worst thing is when you have a finished case, but you have to change 1 component, and it will not fit in.

I will talk about the inside parts longer, later in the soldering steps.

About the case:

The speaker and the case is more like a musical instrument. The speaker can be placed to everything, but it will make different sounds in different materials. There are materials, like wood, PVC pipes, clay etc. what people usually use for making instruments. Some of these are good for making speakers as well, because they insulate the sounds.

The speaker needs insulation, because its emitting sound in the back too, but those sounds are out of phase, and cause cancellations which significantly degrade the level and quality of sound at low frequencies.

If the material is not really good for sound insulation, like an ammo crate box or an actual marble tube it will make noise and distortion, because rigid enclosure reflects sound internally. This can be reduced by internal absorption using absorptive materials (like wool) within the enclosure.

Materials what is good for enclosures: Birch plywood, MDF board

Materials what is the worst for enclosures: Concrete, Steel

Why cork:

I am using Cork-wood because it has one of the best acoustic insulation quality, and it is cheap, easy to handle and very light. Lighter than plywood or mdf.

The cork alone will not stand a chance, because it's really soft for mechanical protection. That is why I made a polyester resin coat for the cork-tube. I put a decorative veil between the resin layers, and that's why it's looks like marble. People usually use polyester resin and fiberglass to laminate boats and ships. Polyester resin is very sturdy, and it can make anything sturdy, but it has a terrible odor, and not easy to work with.

So if you are interested in making a cork+resin case I advise you do it in warmer seasons, because you will need a lot of ventilation, and the resin usually bonding slower in low temperatures.

I uploaded a pic of some decorative foils what I can buy in the local store, but there is a lot of possibilities with these materials, so grab some pencils and draw down your ideas :)

Step 3: Let's Begin: Cut the Frame

After I got everything, i drew the woofer around in the plywood and added +2mm to the circles.

I used the the jigsaw and the drill with the hole cutting heads to make these pieces.

after cutting I sanded down the edges

I put the straight sticks a little farther than the edge, because otherwise i should have sand down the wood to be round.

but i had an easier option, you will see later

To assemble the frame I drilled small holes before I put small screws.

1-1 each side of the straight sticks. Nails can be used as well.

Step 4: Try Fitting the Inside Parts

I had to sand down more to fit the woofer into the hole.

I made bridges for the power bank. The middle one is only secured with 1-1 nail so I can rotate it. In this way I can take it out the battery pack anytime.

Step 5: Make It Round

That's what I said earlier. I put these rods little farther from the edge, I glued some corkwood in top of it, and sanded the corkwood to be round. Sanding the corkwood is much more easier and faster than sanding the plywood.

Step 6: Cutting the Casing

I love to work with cork-wood. I can easily cut it with a serrated knife.

Also Cork's bubble-form structure make it suitable for acoustic and thermal insulation, perfect for speaker enclosure.

Securely fixed the cork-wood to the frame with a lots of glue and some small nails.

BUT ONLY THE HALF OF THE CASING

If you glue the whole thing now, you cant reach the important stuff later.

Step 7: Putting Small Speakers Inside

I cut some small sheets for the speakers, and drew the speakers on top of it.

With the dremel tool it can be easily carved/sanded to make the speakers fit inside.

Important to level the surface, because otherwise there will be big gaps.

Glued these small sheets inside, and then I finished the casing completely.

If the leveling on the sheets are perfect, Later I can glue the small speakers in without a problem.

Step 8: Cutting Holes in the Casing for Small Speakers

I used a hole sawing head from my drills set. Rotated with my hand. Cork-wood is so soft. It was easy to make these holes. It was especially satisfying with the dremel tool.

These holes are needed, because the sound should come out somewhere... But it's not will be visible at all in the end

Step 9: Step 8

I cut the hole for the powerbank. Sanded down the cork-wood case edges.

Now in retrospect I wish i left more edges.

Without edges it was easier to apply the fiberglass veil, but in the finished case it would be good to have some edges to cover more the woofer.

Step 10: Things Unseen

The hole for the power bank slumped slightly. Without the small battery it can't hold itself.

I can't apply the veil and the resin this way.

So I cut some mylar foil and made some wooden wedge to secure and straighten the edges.

Step 11: Paint

White spray on the surface.

Apply the grids after painting.

And paint some more.

Instead of paint, white colored resin can be used as well

The white surface is needed, because the decorative veil is so thin, that without the painting the cork is visible under the veil.

Step 12: Learning From Mistakes

Polyester resin is like working with honey and paper tissues. It's messy, sticky, it's a horror if you are not prepared.

So prepare yourself. Watch some youtube tutorials like this

The most important is safety. Wear gloves and goggles. Especially when you work with fiberglass.

Do it in a well-ventilated room.

Use PETbottles to contain the resin mixture, or something that the resin will not destroy.

Before you start to work cover the surfaces, because polyester resin can stick to everything.

After the resin is bound it will be rigid and stiff but still sticky. So every tool you used is going in to the trash.

Step 13: The Resin

  • Get a 1 Liter plastic bottle (PET bottle)
  • cut it half and pour some resin into the bottom half
  • add the activator. 1-2% is enough, so its like a spoon or something. maybe just a few drops
    If you put too much activator in the resin, it will bound too quickly, and you can't finish the job.
  • So mix the two components with a wide wood stick, stir it like for a minute. Try not to make bubbles.
  • Apply the resin onto the surface with the brush.
  • Stick the decor veil into the resin. Use a small roller if needed.
  • Apply another layer of resin.
  • Stick the leveling fiberglass veil. Use a small roller if needed.
  • Apply another layer of resin.
  • From now on the resin will slowly dissolve the fiberglass and probably the paint too. The whole stuff is like a wet paper towel. In this "wetpapertowel" state it can be formed and smoothed to the perfect shape, especially in the edges.

Beware! Everything is sticky

Let dry for minimum 2 days.

Step 14: After Days and Weeks

After the first coating is dried the whole thing is looks ugly, because the fiberglass is sticking out everywhere.

I applied another really thick coat of resin and let it dry another week.

The result is this extra shiny beauty.

Cut some holes for the power bank.

Step 15: Make It More Realistic

I think the effect was not enough convincing for me, because on a flat surface this shiny marble would look good, but the boombox case is really rugged, so I decided to sand it a bit, to make it more like rough marble.

Also the case was still sticky. So I need it to sand it anyway.

Step 16: Case Is Finished

Colored some of the woofer cover part to copper.

Case is finished, I'm waiting for the amp and the decoder, and I will start soldering as soon I got them.

Step 17: Inside Components

Speakers:

I recycled speakers from an old hi-fi I found in the garbage. There was a lots of useful things inside.

The woofer is 9W 4Ω,

The mid-range is 4Ω, and the tweeters are 8Ω. 1 mid-range and 2 tweeter is 3W. They were connecting in parallel.
Between the tweeters and the mid-range, there is a capacitor in the positive wire. (see in the pictures) I left the capacitor there.

Amplifier:

The old speaker worked with AC so I needed to buy a new amplifier. To be portable the best outcome if it's works with 5V DC, because then I can power it with 18650 rechargeable batteries, and I can charge it with a regular mobile charger or a laptop. Which is the cheapest solution, because it can be salvaged from old laptop batteries for free.

The amp board is working with: DC5V / 2A
It has 2 pin 5V out to power the decoder module.
Left and right channels (satellite) Speaker: selection of 4 ohms (Ω) / 5W speaker tritone.
Bass (woofer) Speaker: selection of 4 ohms (Ω) / 10W-15W subwoofer.

A little bit more powerful than the speakers, which is not a virtue, because it could hurt them, but I couldn't find any cheap boards on the market what is meets my requirements.

Here is a test when I tried playing some Goa-trance on the speakers, the quality is terrible, because I recorded it with my tablet:


That was really loud in live. And the highest Ampere was just 0.25A

Decoder/Bluetooth:

I ordered a cheap 5V decoder module from Dx. It has a bluetooth, it can play from an SD card, maybe even usb. And it's not even that ugly.

There is cheaper solutions to make a speaker bluetooth controlled, like buying a cheap audio adapter or just a board.

But I prefer playing sometimes from usb or SD, so this was on all-in-one solution.

The power source:

This is the Achilles' heel of my speaker.

I thought it would be a good idea to buy a powerbank on a sale, because it has all of the protections, what is needed
(over charging, over discharging, over current and short circuit protection) but it backfired because it has an automatic shut-down if my devices isn't drawing a lot of power, since it's meant for charging cell phones.

(There is a solution for this problem here: https://www.instructables.com/id/USB-External-Batte... )

I'm currently still waiting for the bluetooth decoder, so maybe that will save me. (Because I do not want to hack my powerbank.)

But probably not will save me, so I always have a plan B.

The plan B is recycling old 18650 batteries from a laptop and building a new powerbank. It doesn't need to be a high drain battery or really powerful something, because this is a small amplifier with really low consumption.

Do not buy cheap batteries on Ebay like Ultrafire, Aw, Olight, Efest... They are totally fake.