Bluetooth Crib Speaker

Bluetooth Crib Speaker

       I really liked the idea of setting up a speaker in my daughter's crib so she could listen to music when going to sleep, but all of the ones I found on the market were ridiculously expensive and made the crib look like Fisher Price vomited on it. Perhaps worst of all, they used some strange media known as a "Compact Disc", which my research tells me is how ancient peoples listened to music before the advent of lossy audio codecs.

I decided that the best solution to the problem was to build a speaker of my own design rather than spending ~$100 USD on something I didn't even like. The most important part for me was to make the finished product look like a part of the crib, not some plastic garbage clamped onto the side. Everything from the shape of the device to the materials used would be influenced by the crib it would eventually attach to.

Originally I was simply going to build a case around a cheap MP3 player, but quickly realized that had quite a few problems. For one, I would need to constantly be putting new music on there as we found new things that she reacted well to; but more importantly, we would have to fiddle with the thing every time we wanted to change the tracks or adjust the volume. It seemed counterproductive to have a crib speaker, which is supposed to relax the baby, if one of us had to come into her room and make noise just to control it.

After some thought, I had the idea of building a wooden case around a Bluetooth media player. This would let me stream audio to the speaker from my phone or computer; that way I could change tracks, adjust the volume, and pause/stop the music without ever having to open the door to her room.

Speaker Cabinet

       The only part of the design I had figured out for sure in my head when I started this project was that I wanted the finished product to actually look like a miniature speaker, not some ugly kid's toy. It would also be stained to match the crib itself and all of the hardware and details on the speaker should blend in with the existing design.

The first step was to go to the store and get some decent looking wood, in this case 1x3 furniture-grade pine, and make a tiny speaker cabinet. I measured the space between the side slats of the crib, and came up with some rough dimensions that would put the speaker grille right between them.

The first version of the speaker cabinet measured 89 mm x 137 mm (3.45 in x 6 in), and felt very sturdy. I was initially pleased with it and started to plan out the rest of the design, but quickly started seeing some serious problems. For one, the 1x3 wood was rather thick for such a small cabinet, so the internal dimensions were only 49 mm x 98 mm (2 in x 4 in). This was a little tighter than I would like, though not completely unworkable. The bigger problem though were the aesthetics; the thing just didn't look like a speaker cabinet. The frame was too thick, so the proportions between cabinet and grille would be all wrong. Cabinets

I went back to the store and found 3/4 x 4 poplar, which had the right thickness but was too wide. So I ripped it down to 3 inches on a table saw and made a new cabinet with more or less the same external dimensions. Since the wood was thinner this time around, the same external dimensions gave me more space internally, and the cabinet overall had a much more proportionate look.

Now that I had a basic frame I was happy with, I needed to start considering how the thing would actually work. I originally intended on making one side of the cabinet open up, sort of like a jewelery box. This probably would have worked, but the logistics became difficult the more I thought about it. I eventually came up with the idea of putting the speakers and electronics on a sled of sorts, which would have the speaker grille on one side and the back side of the speaker cabinet on the other. This design had the advantage of putting all of the electronics on a removable platform, and didn't require any hinges or latches. The only problem was that the dimensions would need to be carefully measured so that the grille ended up flush with the cabinet when the sled was put into place.

The Button Problem

       While I was planning this whole thing out in my head, one issue kept coming up blank: what I would use to turn the thing on and off. The Bluetooth media player, similar to many Bluetooth headsets, required you to hold the "Play" button for a few seconds to power on the device; so I knew I needed a momentary pushbutton, but besides that, I had nothing. I looked for a few weeks, but all the momentary buttons I could find were ugly plastic, and none of them came even close to the look I was going for.

For awhile I entertained the idea of making my own push button, using a small piece of stained glass, lit with a blue LED, attached to some kind of spring actuated contact. The idea was that you would push down on the little square of glass, which would light up when the device was powered on with a soft diffuse glow from behind. It would have looked really cool, but I couldn't wrap my mind around a reliable way to handle the mechanics in such a small space that wouldn't take longer than the rest of the project. It went this way for quite some time. I worked on other parts of the project, like the case and electronics, and did my best to ignore the looming problem of how to actually turn this thing on and off.

Then one day, I was thinking to myself: "What kind of momentary buttons are decorative, and ideally lighted?," and the answer hit me. It was so obvious, I couldn't believe I didn't think of it before. A doorbell! I immediately went on eBay and started searching for doorbell buttons, and within 10 minutes I found a button by Baldwin that was exactly what I had in mind. The plate had a wonderful antique bronze look, and it was the perfect size for the back cover of the speaker cabinet.


Feeling The Blues

       Up to this point, I was pretty happy with the whole project. I had something that looked acceptably like a speaker and a pretty good idea how to make it all work together. The only thing left was, what I assumed, the easy part of fitting it with some appropriate Bluetooth electronics to turn it into a functional device.

Unfortunately, this is the part of the project that never actually worked out. I spent months picking up different Bluetooth audio devices on DealExtreme and eBay, taking them apart, and getting furious.

OK, let me rewind this a bit for you. Before I started putting this whole thing together, I went on DealExtreme and picked up a Bluetooth media player for $15 or so, connected it to a small external speaker, and did some basic tests. How far could I get from the thing before it lost signal, what kind of volume control I could expect, battery life, etc, etc. All this went smoothly and encouraged me enough to start the construction of the speaker cabinet itself. Once that had progressed to the point I was ready to start fitting electronics into it, I went back to get my Bluetooth media player and discovered that, oddly, it no longer worked.

Searching online, I found out this was actually a very common problem. A good portion of these devices are defective from the factory, and stop working after a few hours for who knows what reason. So to be sure I had a working unit, I need to order a few of them and implement a "stress test" of sorts where I would run each of the media players for a few hours connected to an external power supply and speaker just to weed out the ones which were defective. Switch Leads

This process worked, and after ordering 6 of these devices, I was left with a couple of them that appeared to be functional.

But then there was another problem. The first device I tried delivered very good audio on my set of external speakers, it sounded loud and clear. But these new ones sounded like trash. The audio cracked and hissed, and the volume level was so low that, unless my daughter was sitting in absolute silence, there was a good chance she would never even hear the thing. For a device that was supposed to sooth her, potentially when she is in the room crying, this was obviously not acceptable.

For awhile I had toyed with the idea of packing an audio amplifier circuit in there with the Bluetooth device, but then I hit the final problem that damned the whole project.

The internal construction of these adapters was so poor that it made the necessary modifications nearly impossible. At the absolute minimum I had to relocate the power switch and activity LEDs to the doorbell, but even a light handling of the player's PCB would occasionally cause components to fall right off the board.

Time's Up

       After all the delays with the shoddy Bluetooth devices, I simply ran out of time on this one. By the time I was ready to give up on the cheap Chinese Bluetooth media players and graduate to something that actually cost more than lunch at Wendy's, my daughter was past the point where this would do her any good. It turns out that children age at a rate that greatly exceeds my ability to focus on a single project.

Ironically, my daughter turned out to sleep easily anyway, and we never need to play her any music or that kind of thing when it was time for her to go down, she always went directly to sleep.

Perhaps I will revisit this one for the next child. If I do, one thing is for sure, I'll spend a few more dollars on the internal components instead of trying to make some cheap garbage do my bidding.