Introduction: LOUD and Portable, Rechargeable, Bluetooth Speaker

About: I love learning and tinkering...

I wanted to build a powerful bluetooth speaker that was portable, rechargeable and water resistant, something rugged I could take to the river and camping, or put into the basket of an adult trike.

I used Van Damage's excellent build as inspiration. Thank You!

The Supply list ran longer than I could ever have imagined, but the finished product is a BEAST!


Step 1: What Case to Use?

The first step was finding an appropriate case to house everything. I wanted something small enough to transport but big enough to be loud. Specifically, I wanted an 8" Subwoofer and two Midrange speakers. My best scenario would be a case that is waterproof - gotta keep moisture and sand out. I was gifted a used Seahorse case that has worked out very well!

Step 2: What Parts to Use?

Next, I needed to source the parts. The finished speaker had to have bluetooth connectivity. I found the Cerwin Vega bluetooth receiver. It is a rocker switch that fits a "Clearing" mount, is water resistant, and controls whichever device is connected. It also includes an AUX-in 3.5 plug to allow additional audio sources. I wanted a voltmeter (to keep track of battery level) that also had USB ports to recharge a phone or other device. The speakers I used needed to be water resistant and handle a good amount of power. I shopped around until I found some that were equally cost-effective and of good quality. The MB Quarts are 6.5" and the 8" Subwoofer is a Sound Storm Labs product. I used amplifier boards to give life to the speakers: one for each speaker & subwoofer. I powered everything using two 12V batteries ran parallel - this keeps the voltage at 12 but significantly increases the length of time between charges. I installed a power button to keep everything on/off when appropriate.

Step 3: Speaker Placement

Once I received everything, I placed the speakers and subwoofer on the front of the box to determine best fit. In hindsight, I would've gone with a smaller set of speakers so that they would mount a little easier to the case. The Seahorse is rugged, and one of the ways it stays so is the ridges that run along the front of the case. In the pictures you may notice the ridge that runs about 1/3 of the way across the length... this separates each portion, which are at different depths. When I cut the holes out of the case, working with two different depths was a challenge. Mounting a speaker over two depths is not good. After doing so, I decided to re-mount the speakers from the inside. This worked out much cleaner, but I lost use of the supplied speaker grills. I ended up finding some steel mesh to fashion my own grills from. This made for a more streamlined case, with fair protection for the speakers.

Step 4: Recharge It!

Because I wanted a portable case, I needed a good way to plug it in to recharge the batteries, but didn't want the fuss of a cord when out and about. The solution was using a connector plug like those found on a computer power supply - a C14 Inlet Socket. It is simple enough to use plus it keeps the water and sand out (I store the cord inside the case when not needed). I connected a trickle charger to this connector plug internally and it works great. I ran two batteries in parallel and then connected the charger to that setup. The voltmeter will let me know how much power I have. Truthfully, I didn't need two batteries; this box runs and runs without being recharged plus losing the weight of the second battery would be nice. That said, this case has wheels - so not too bad either way.

Step 5: Installing and Wiring Amplifier Boards

Wiring the amplifier boards was straight forward. I included the voltmeter and bluetooth receiver into the mix, wiring everything through a waterproof power switch. The Cerwin Vega bluetooth receiver can be wired to turn off everything but I like the switch for ease of mind - no accidental powering on.

Step 6: Testing... Testing... and Adjusting

With everything connected, the sound is LOUD! One problem that I ran into was a hum coming from the speakers. It turned out that there was a ground loop in the wiring; I solved this by installing a noise isolator. Another thing I noticed was that the softest sound was still too loud; I solved this by installing a level controller. This case now has a clean, clear, and moderate sound that gets as loud as anybody could ever want!

Step 7: Finishing Touches

With all the components wired and tested for quality sound, I installed foam to keep everything neat, plus it acted as a baffle to keep the case from vibrating the components. Digging into my supply of random parts, I discovered some Dynamat so used that to strengthen the lid of the case. I also used a little silicone adhesive to keep the speaker wires in place. I used Velcro to attach the cord inside the case; it rests above the frame of the old computer power supply. This worked out well to keep the C14 Inlet Socket and trickle charger isolated from everything else, not to mention hands when plugged in for recharging.

Step 8: Considerations for Next Build

Rather than use the rocker switch-styled bluetooth receiver, I would use something like the JL Audio MBT-RX instead. This would be one less hole to cut into the case plus it includes better bluetooth sound (Qualcomm aptX audio codec). Another thing I'd change is using a lightweight, single battery. This would significantly reduce the weight of the case while still not needing to charge too frequently [NOTE: I charged the case two weeks ago (installed with two batteries), and have put about 32 hours of use on the single charge].

PROTIP: find the case you want to use first, then shop for speakers that fit within the contours of the case; I would've saved myself some grief in getting speakers that would install cleanly between the ridges of the Seahorse case. Happy Building!

Audio Challenge 2020

Participated in the
Audio Challenge 2020