Boombox Project: The Riese

[Gordy]

Earlier this month I posted on the Tech Talk forum that I had the grandiose idea to build a Class D amp, bookshelf speakers to match and integrate DSP. The more I thought about it, the more I lost interest. I unfortunately don't have the dev time to devote to that kind of a project right now. I still have the creativity bug but decided to follow through on a promise to my near 7-year-old. She sees me build boomboxes and for the last few years she has asked when I will build her one. So, I bought some parts to make a small speaker box and they have just been sitting for the last 2 years.

Since her 7^th birthday is coming up, I think it is time to follow through on the promise except I won’t be using that box of parts. Once I get it built, I will take it back apart. Part of the exercise is she will help me reassemble. The initial idea was we would build it together. But, in order to keep this as some-what of a surprise for her birthday coming up, I will R&D and build beforehand.

Requirements:
1. Must be under 6-8 lbs
2. Battery powered
3. Not be loud enough to hear throughout the house
4. Use parts I have on hand
5. BT connectivity, will not have line-in capabilities

We will get her an iPod Nano to use so she can connect. This will also allow the wife and I control over what she listens to and the wife can load music on it at will. She is a very hands-on kid. She works out in the shop with me and is a master crafter and Lego builder. She also has her own sewing machine and knows how to use it. I think building a speaker box should not be too much of a stretch. For the enclosure, I used BassBox6 Pro.

Electronics:
Drivers: TB W3-1053sc
Amp: Adafruit MAX98306 Amplifier
Bluetooth: Sure BRB1
Battery: Adafruit 18650
Charger: Adafruit USB LiPoly Charger
AC Adapter: Adafruit 5v 2A w/2.1mm plug

Enclosure Specs:
External Dims: 11.75” x 5.75” x 5.75”
Internal Volume: .125 cuft (single enclosure for 2 drivers)
Port: 1” x 1.653”
FB: 93hz
F3: 80hz

I did a mock up in SketchUp with a little larger dims. This was before I was able to find 3/8" MDF. That allowed me to knock off 1/4" off the below dimensions. The 3/8" MDF should also help with the weight. I built a test box this weekend and will post some pics in the next post.

[Gordy]

The outer shell is 1/2" MD. The baffle, grill and back are 3/8" MDF. The braces that the back attaches to is scrap hardwood 5/8" x 1/2".






The W3-1053 really needs a 3-1/16" hole to mount flush. I was too lazy to get the circle jig out so a 3" forester and a chamfer bit worked nicely.

[12v]

Nice, I'm subscribed. Can't wait to see the finished project, love all of your work!

[Gordy]

This box I am building is a prototype more or less. I am seeing how everything fits and works together. Once everything is sorted, I will build the final box. Getting the electronics worked out is next. The holes on the edges are fro the screws that will hold the back on and the other holes are for the elctronics. The charger is held in place with brass standoffs and the BT module uses 1/4" nylon spacers.

I think folks would be surprised at how loud this little box will get. I have been listening to it for the last few days and it sounds pretty darn good. You can hear the low end and the grill cloth just cuts the brassiness of the highs down. I see posts all the time with folks trying to get a ton of wattage out of their setup and sans a box being used outdoors or in a large open space I just don't think there needs to be a lot of power. The Adafruit amp also has 4 output db settings. I have it on the highest setting but will probably knock it down a few for my daughter. The Sure BT module is not one that PE or anyone stateside sells. It looks like they Sure no longer sells the old 2.1 module that had issues with noise. the BRB1 does not have any noise and is voltage versatile. It can run 12v or 5v. It also does not have the amplified output that the 4.0 module. For the price, you will not find a better 2.1 BT module

The charing board is also Adafuit. It is powered by 5v and has several outputs that makes it pretty versatile. There are LED outputs for charge state, one LED for charge, and another LED for charge complete. I am going to use a dual color common anode LED so charge/charge complete are in a single LED. It has JST PH and PC board solder points for the battery and load. You can use all 4 or a combination of the 4. Via a resistor on the board, you can control the charge rate as well. Factory settings are .5 amp, I take it down to .3 amps. It generate less heat and does not take that much longer to charge. It also has full over an undercharge protection. The battery is an Adafruit 18650. They recommend their battery as they state their charger is tailored to the chemistry of the battery they sell (INR). I have used other batteries and not has an issue.

I will be replacing the components used in the final box and add JST-XH connectors where the green terminals are. This will allow my daughter to just "plug in" the wire harness when she helps me assemble. The final box will also be covered in a slate colored (black, charcoal, grey) fabric tweed as this is what she picked out. It is automotive tweed and is extremely durable and can even be cleaned with chemicals. It is tough stuff. It will have black grill cloth and nickel corners. I am going to try to find a scrap piece of walnut I can use for the back.









This is the first time I have used this type of push button switch. the LED that indicates power on is rated at 12V and works just fine at 5v.










The speakers connect via a JST-SH connector which allows easy removal of the back.

[Millstonemike]

Slick, using the amp's gain output will like a governor. Liking your JST crimp tool?

Waiting to see the woodwork.

[Gordy]

I hate to disappoint but I don't think the woodwork on this one will be extensive. If I can find a scrap of walnut or mahogany I will use that for the back. If the box was for me I might make some translam boards out of Baltic birch and use that for the box exterior

And yes, the gain will be perfect as a governor. It comes with the parts to make it selectable. The crimp tool is a game changer. It allows connections to be removable and reliable.

[Kevin K.]

Where did you get the power switch? Might be interested in using one like it in the future, thanks.

[Gordy]

It is a pretty cool switch. Most switches like it are momentary not latched. There are some voltage limitations but the do come in several colors and also come in a black housing. Search amazon for Ulincos Latching Pushbutton Switch. The switch has a choice of NO or NC making it a good candidate for the new Dayton BT/Amp combo boards.

[Kevin K.]

It is a pretty cool switch. Most switches like it are momentary not latched. There are some voltage limitations but the do come in several colors and also come in a black housing. Search amazon for Ulincos Latching Pushbutton Switch. The switch has a choice of NO or NC making it a good candidate for the new Dayton BT/Amp combo boards.

Thanks for the info. I agree, very cool looking switch! BTW, nice project and I'm sure your daughter is going to love it, especially since "Daddy" built it and she will get to help on the final assembly.

[Gordy]

I built the final box this evening and the glue is drying. I was able to find a scrap piece of walnut for he back. I had enough height on my table saw blade to make a few passes and I was able to surface plane it down to 3/8". I also got the JST-XH headers and plugs today as well for the amp, charger and BT module. I should be able to get the box covered tomorrow. It will be my first time using a fabric.

[Gordy]

I was able to finish it up today. It took longer than I thought as this was my first time to cover a box with a fabric. But I have to admit, I like the tweed and the feel of the box. I also have some lighter beige as well.

After assembly of the final box and after the glue dried overnight, I used my Dewalt random orbital sander to square everything up and smooth out the ends. With 80 grit it does not take long and it removes a good amount of material pretty quickly.




After everything is square, I routed all the edges with a 1/2" radius. this is a requirement for the nickel corners that will be used. The two holes in the baffle are for the charge LED and the #8 truss head screws that will hold the grill on.




The top get covered first then the sides. That was the last part to wrap is the bottom and seam. The line is drawn on the bottom in the middle of the box to act as a guide. I will use it with a straight edge to do the final trim on the tweed for the bottom seam.










The good thing about the nickel corners is that they cover most of the corner on the front of the box. This allows for a little error when trimming the material.






The grill and the back have to be fitted. Since the tweed that is wrapped around the edges takes of ~1/32" the grill has to be trimmed to accommodated this plus the grill cloth. goal is to get a snug fit. The back also has to to be trimmed to fit as well.

[Gordy]

Next up is the electronics. Some of the parts will be removable for her to install and some parts will stay installed like the power switch and DC jack.

The charger and amp board have their stand offs attached and the holes are predrilled into the back. I apply hot glue to the holes on the back and set the parts in. Once the glue dries they are very solid. It also allows them to be removed if need be.




I used a 2 & 4 pin header for the charger to connect the power input and the led status indicator.




A 4 pin header connects the line-level to get signal from the BT module to the amplifier. A 2 pin header connects power which is tied to the 2.1mmm plug on the BT module. The wire terminations and splices are under the BT module to keep everything neat and out of the way,








The 250uf cap should keep the speaker from going to low and is inline with the tuning of the box. I used a JST-SH connector so that when it is reassembled it is easy for my daughter to plug in.









I tried several different configurations. Too much pretty much emitted the base. No damping made it sound boomy, and a square on each side of the box ended up working just right.

[Gordy]

The last is the grill. It is not easy to get the grill cloth lined up but I have used this method several times and it works pretty well. Once the grill is lined up on the grill you just tighten down the clamps and staple around the back of the grill. It pulls the cloth tight and keeps a semi-uniform staple line around the back of the grill.














The charge LED is invisible unless it is plugged in and charging. Once it is completely charged, it will change to green.

[Kevin K.]

That is some awesome looking work Gordy! Bet your daughter will be grinning from ear to ear.

[12v]

Love it! Another great job you have done. I love the fabric. Your daughter is very lucky!