OMGWTFBOOOM

Now, I know what you’re thinking, ‘What the hell kind of title is that? Well, I have been busy lately with kids and work and my usual environment for writing has changed for the better but is no longer as conducive to me getting any writing done.  So, now I am picking a different time-slot to put together something for reference when I come back to change things.

To properly set the stage I need to give some background.  I am part of a local group of IT folk who tend to do things together, on our Slack channel someone posted that they have a set of old home theater speakers free for whomever wants them.  I had designs to build good sound for my living room television, along with a more secure cabinet and whatnot.  I got the speakers, they were some high-end Polk Audio with solid enclosures, after removing the protective screens all the drivers appeared intact. I was excited.  Then I started shopping for feature rich receivers and the price made me shy away, never mind the amount of work it would take to build a cabinet to fit in the space and I would have no way to protect the drivers from the errant Hot Wheels car thrown by a child not getting their way, so the speakers sat in my office taking up space.

Fast forward to a few weeks ago I was going down the rabbit hole on YouTube (Google’s term) and I re-discovered people making their own Bluetooth powered speakers.  While watching one of the videos I happened to look over at the 6 speaker cabinets that I had just taking up space in the corner of my office.  Longer story short I had done some cleaning, my workbench was available, and the tinkering could begin.

First some research on what I had and what it was capable of; 1 CS1000p Powered Center Channel, 2 FX500I Surround Speakers, 2 RT800I Floorstanding Speakers, 1 PSW450 Powered Subwoofer.  Right off the bat I had keyed in on some terms that piqued my interest, specifically ‘powered center channel’.  I hefted this beast on to the work bench and now it was time for discovery.  On the back of the CS1000p, there were 2 screw down inputs one for mid/high frequency and one for low, an RCA jack for subwoofer, a switch for high level input on and off, and a traditional power input.  On the front I could see a total of 5 drivers, what appeared to be 2 woofers, 2 drivers for mids and a single tweeter in the center, there’s also a volume knob and a green LED.  I did not see a power switch of any kind, so I assumed that this was an always on sort of thing.

Next step was to test functionality, I broke apart a headphone cable to get leads that I could connect to the inputs on the back, I powered the speaker up, connected it to my tablet, and nothing.  The speaker powered (evident by the green light on the front) but nothing was coming through the drivers.  Well, this may end up being a little more difficult.  Time to break out the trusty screwdriver and let’s see what’s inside.

The first thing I noticed was that there were a bunch of screws on the metal back plate.  I pulled what appeared to be the screws holding the plate in place and was able to remove it from the enclosure pulling it away and disconnecting the cables attaching the guts to the drivers.  I was able to mostly identify what circuitry was at work here.  I had 2 channels but unsure which speakers they were attached to and some thinner gauge wires I assumed for the volume knob and the LED.  Still attached to the plate were a power conditioner, what appeared to be an amplification board, and a power converter from AC to DC power.  Upon closer inspection the plastic housing around the Subwoofer input and the Switch for High Level input looked like they either had some weird epoxy around them, or they had melted.  I had a hope for epoxy but turns out they were melted.

Now is the point where I must interject that I do not have very much electrical knowledge, but I usually have an approximate knowledge of what I am looking at.  I was able to identify the amplification chips and put together a rough idea on the path of audio signal.  I wanted to try one more time to power the components and push audio through, but the results were the same as before.  The parts on the back plate were going to have to be replaced.  Okay, let’s look at the drivers.  A couple hundred screws later I was able to get part numbers on the individual drivers and get what their power rating was.  I also found that there was a crossover board behind the center 3 drivers, which handled throwing the highs to the tweeter.  Some shopping and YouTube lead me to a replacement amplifier and Bluetooth module.  The video made everything look simple.

Being one to like having multiple opinions, and not wanting to throw a bunch of cash at a learning project I looked around to see what others were doing.  I then stumbled on a video where someone had found an amplifier board with Bluetooth built in (Hey, less wires!) and it was cheaper than the separate boards, I also found that it had a bunch of extra headers for expansion.  Almost like this board was built for this specific purpose.

The board in line for purchase is manufactured by Dayton Audio, it is a KAB-250v3 it delivers 50 watts to left and right channels (remember I have 2 channels inside the speaker) it’s a Class D amplifier board, with Bluetooth 4.0.  In the box it has the board and wiring harnesses for power, speakers, a Bluetooth pairing control button and an external Bluetooth antenna.  Also, in the box was a quick-start guide, which was just detailing out which headers are for what feature.

Right about here is where the anxiety set in.  In the past I have caused some irreparable damage to 12v electronics by being careless, so I wanted to be extra cautious, I had monetary investment into this project at this point.  Before moving forward, I wanted to make sure that the speakers and my amplifier would be compatible.  While on an errand with my wife we were close to a music store that sold pro audio equipment, I gave it a shot, talked with their pro-audio guy.  He gave a bit of a shrug and said, “I think you’re just going to have to be brave.”  He did clue me in to make sure that the impedance of the drivers matched up and to start low before going bigger.

Okay, moment of truth.  Time to test the Amplifier board with a single driver.  I pulled the driver out of the enclosure and put together a bunch of temporary connections, time to power everything up.  The outlets on my workbench have individual switches to turn them on and off makes it nice for instances like this where I can flip a switch faster than I can frantically unplug something.  I checked all of my connections to make sure I had continuity in all the places I should and then flipped the switch.  I don’t know what I expected, maybe some sort of startup noise, a flourish of non-existent LEDs, something.  All I got was a single green LED on the amplifier board and a little EM feedback or coil whine (I assume) on the driver.  I pulled out my phone and set off to discover Bluetooth devices and there it was “DAKAB”.  Initial pairing was a little shaky, but I really think I just didn’t have a handle on what the controller button actually did.  I got paired and time to fire up Google Music and hit play on a playlist and I immediately find that my Bluetooth volume was set to max.  But it worked!!!

I did a little happy dance, my wife laughed with/at me, and now it was time to test the rest of the enclosure.  I broke my temporary connections, reinstalled the driver, connected to the channel and re-ran the test, another success!  One more test, this time powering the whole enclosure and one more success! Now it was time to plan out how I wanted to tuck this all back in to the enclosure to make this fully function.

I opted to continue to use the AC to DC 12V 1.5A converter that I had on hand, just connecting it to the AC conditioner that was already present.  I used Butt connecters for all the connections cause a more permanent solution would be further down the evolutionary path of this project.  About an hour of testing connections and wire management I was able to fully re-assemble the enclosure and a final test to mark the completion of version 1.0 of what I have titled OMGWTFBOOOM.

What I have right now is a surprisingly capable powered Bluetooth speaker.  My plans for the future of the project is to re-surface the outside of the enclosure to introduce a little bit of weather resistance, replace the soft cover on the front with a metal grate of some form, and add wheels cause this thing is understandably a bit on the heavy side.  Additionally, I would like to put together a better method for delivering power and including a battery for some true portability.  Some more upgrades down the road would be an auxiliary input and some USB power for extra functionality.  Last, I would like to add a paint-job to complete the cosmetics.  But as with all projects, this will be a full evolutionary process.

One thought on “OMGWTFBOOOM”

Comments are closed.