Omni-Directional BoomBox

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Omni-Directional BoomBox

Postby Josh Hess » Thu Jun 04, 2015 12:41 am

A few years ago in high school, I built a high power speaker system to go in one of my spare backpacks. You can see a video of it here if you are interested: https://www.youtube.com/watch?v=J4nScktnmIw
Anyway, I have been using it for music at get together's, parks, tailgates, etc and I thought it was time for it to lose its incognito backpack facade and be rebuilt from the ground up.
I started working on ideas for the new design about a week ago and decided on an omni-directional design unlike anything I have built or even seen before. Here is a picture of one of my early concept drawings:
Thunder Pod Speaker System.png
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It is broken up into chambers from bottom up, it goes "Electrical, Subwoofer, Subwoofer gap, Speaker Enclosure One, Speaker reflector, Speaker Enclosure Two" This design also allows for a modular enclosure/speaker system.

I will post more pictures and progress throughout the duration of this project!
Science may set limits to knowledge, but should not set limits to imagination.

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Re: Omni-Directional BoomBox

Postby Josh Hess » Mon Jun 08, 2015 2:40 am

Although unmatched in price to capacity ratio, I think I am going to reconsider using Lithium Polymer batteries: https://www.youtube.com/watch?v=pkO4sn0 ... mw&index=1
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Re: Omni-Directional BoomBox

Postby Josh Hess » Mon Jun 08, 2015 3:39 am

A lot has been done with this project so far and i have not had the time to post it until now, so this post will have a lot of pictures and information!
After about a week of brainstorming and revision of the design, I was confident enough with it to start fabrication. Due to the modular design of the upper speakers and electronics-, I had to build the frame around the subwoofer enclosure. I built the enclosure out of 1/2" furniture grade plywood which unfortunately is too thick for the the laser cutter I am using to cut so I engraved the pieces into it and then cut them out with a jig saw.
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Here are the pieces cleaned up and dry fitted together:
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You can see the corners are missing. This is intentional to allow for the four "pillars" to be added later to created the modular frame design.

Next it was time to do some rapid prototyping of the modular speaker enclosure. Once the plans were drawn up on inkscape as vector models, it was time to cut them out of foam board.
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You can start to see how this design will come together once the frame is in place.

The next step was a bit tricky. For the corners, I wanted a rounded edge, so I picked up some 1.5"x1.5" oak posts and had them cut corner to corner on a band saw. These would be the main structural supports for the frame so I needed them to be strong. It was bit of an order of operations trick to get it together properly. First, 5"x1/2"x1/2" strips of scrap were cut and screwed 5 1/2" up from the bottom on corners of each oak piece. Then once clamped together, the top and bottom of the sub enclosure were screwed to those strips.
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The last thing to do was start prototyping the omni-directional reflector. This was done basically the same way as the speakers. I decided to retain the same modular mounting mechanism as the speaker enclosures and prototyped it out of the same foam board material.
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This prototype had two different pyramids with different angles. One was a perfect 45 degree angle while the other was slightly less (around 30). This was done to see if the reflector could be compressed to save vertical height. After testing, it was concluded that the difference in clarity especially in the highs was substantial enough to use the 45 degree reflector. Then it was back to the laser cutter to cut both the reflector and the speaker enclosures out of 1/4" plywood.
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For Testing purposes, the speaker enclosure was positioned in between the frame for easy adjustment. The reflector works great and looks pretty cool as well. Well, most of the woodworking has been done, the next step in this project will be planning out and finalizing the electrical system. I will post the progress on that once sufficient steps have been taken and I have the time.
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Re: Omni-Directional BoomBox

Postby Josh Hess » Sun Jun 21, 2015 11:57 pm

Much progress has been made since the last post! After many design iterations of the electrical system, I have settled on a design and have acquired almost all of the parts necessary.
Here is an overview of the design evolution:
Electronics Layout.png
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And here is the final design:
Electronics Final.png
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I have also begun the integration of the electrical system and wire management into the wooden frame by cutting out notches in the posts for wires to run. Later, there will be finished lengths of wood cut out to cover these faces.
As shown here, the notches were cut using a routing bit on a dremel and the middle pried out:
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Also not show, the top and botom plates were cut out and fitted. The top plate has a handle for easy carrying and acorn nuts while the bottom has rubber feet. Here it is all together:
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Much work has been done with the planning of the electrical system and its assembly should proceed this week with minimal delay. I have not gotten any pictures of my initial tests with the electrical system, so I will post a basic sketch of the electrical circuit.
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Once again, I will post when both progress is made and time is available for me to do so!
Science may set limits to knowledge, but should not set limits to imagination.

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Re: Omni-Directional BoomBox

Postby Josh Hess » Mon Jun 22, 2015 11:19 pm

More progress was made today than anticipated so I have decided to update this post. I will start by giving a parts list of the electronics used and on the way.
Batteries: Samsung INR 25R x28 http://www.illumn.com/18650-samsung-inr18650-25r-2500mah-high-discharge-flat-top.html
Amplifiers: 300w mono T-Amp x1 http://store.sure-electronics.com/aa-ab31194, 100w stereo T-Amp x1 http://store.sure-electronics.com/audio/aa-ab32971-1444
Volume Control: http://store.sure-electronics.com/aa-ab41134
Bluetooth Receiver: http://store.sure-electronics.com/audio/aa-ab41136-1444
Laptop Bricks: 20V 4.5A 90W AC Adapter For IBM Lenovo http://www.ebay.com/itm/311358550182?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The first thing to do was cut out all of the wooden parts that make up the electronics assembly:
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I also made an experimental battery holder for the 18650 cells. I was unsure if it would work or not due to some extremely thin parts but it seemed to work alright.
Here is the wooden holder:
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And two of them used in one of the assembled packs:
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Next it was time to work on the main electronics assembly! In order for the two amplifiers to fit, the preinstalled fan on the heatsink had to be removed. After some crude testing, I determined that the heat from the amps could be dissipated via airflow over the heatsinks without their own independent fans. However, more testing will be done later to confirm.
Here is the amp with the fan off:
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And a comparison with and without:
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Here is the electronics assembly starting to come together with the battery packs and amps installed:
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Another thing I did today was fit the laptop adapters and manage the cables. The adapter covers are molded with little "feet" or bumps on the bottom of it. Not sure what the purpose of these are, but they inhibit the adapters from freely sliding into the frame so they are filled/sanded off as shown below:
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Another thing to note is that there appears to be two flavors of this adapter one being sligltly bigger than the other. I got three slightly larger ones and one smaller one. The bigger ones had a higher lip around the label, so this was simply filed down until it too slid freely into the frame. (this size difference could be accounted for by re-sizing the hole before cutting as well)
Here are the two different chargers,the darker label one being the smaller:
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Here the adapters are installed in the frame:
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The last thing I did today was the amplifier plate assembly as shown below:
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Well that's it for now!
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Re: Omni-Directional BoomBox

Postby Josh Hess » Wed Dec 16, 2015 11:58 pm

I's been a while since I have updated this log, not because there has been no work done, but because I have so little free time for me to document the progress. Lets begin. To start, the Amp/Audio assembly has been fully assembled. The following pictures show the testing setup of the completed audio assembly:
Testing off of battery and Boost Converter (for sub amp):
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One of the things that I did not realize when purchasing these amps is that the minimum voltage rating is not the minimum voltage for maximum output. If the proper voltage is not supplied, then the amp will simply clip at a lower gain value than its advertised value. In other words, the recommended voltage is required for ideal operation. Since my power source was to be the 20-29v laptop bricks/battery packs, not enough voltage would be provided for the subwoofer amplifier to operate properly. I ended up getting a boost converter, which is a high efficiency dc-dc converter that boosts the voltage. I was able to bring the voltage up to ~40v and increase the gain without clipping to the proper output power. While I was at it, I also got a buck converter for the 12v bluetooth receiver and active crossover. This is similar to the boost in operation, but lowers and regulates voltage as long as the input is grater than or equal to the desired output.

It may be hard to see here, but notice the molex connectors at the end with the wires sticking off (also seen in picture above). This is going to be used to establish a connection between the audio assembly, power assembly, and the speakers themselves when installed in the electronics area:
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Testing with power and fan assembly (notice the molex connectors):
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This reminds me of a short story I would like to share about this project in this stage. I ended up taking this speaker back to my dorm to store wile the lab I was working in was closed. While there, I had it setup just like in the picture above for testing and listening purposes. Apparently, one of the supervisors doing health and safety inspections thought that this resembled some sort of bomb, so much so that they invited a police officer to come visit my room. Luckily, I was present downstairs before the cop showed up. Upon arrival, he stated to the supervisor that if there was a threat in the building, that it must be evacuated and then a bomb crew sent in to "detonate" it. At this point, I offered to show him pictures of the project to prove that it was not in fact a bomb and that it was simply an engineering project. Thankfully, that resolved the issue and I decided to not bring the speaker back to my room until it had no loose external wires. Anyway, back to the build log.
After listening to it for a few weeks with content that I was very familiar with, I determined that the amplifier for the subwoofer was not powerful enough for my liking. I ordered the 500 watt variant of the original 200w amp that I had. This was the same form factor, but required slightly higher voltage to operate. This was not a problem as the voltage coming from the boost converter was a quick adjustment up to 50v.
Another change I made to the existing design was replacing the main full range drivers. I attended the local maker fair here in Orlando, and got talking to some guys about the speakers they had built. The speakers looked like typical floor standing speakers, but with two low end drivers and this little 1.5" speaker. They sounded quite good and when I asked them what they had the crossovers set to (expecting them to say the little thing was a tweeter and the woofers took care of everything else) they said the little thing does 200-20,000hz and the woofers are 20-200hz. I didn't believe them at first but they quickly convinced my by covering the little one with their hand. All of the rich sound, the detail, everything diapered! I asked them what it was and they explained how it was a new technology called BMR. Anyway, long story short, I found some of them on parts express here: http://www.parts-express.com/tectonic-elements-tebm46c20n-4b-bmr-3-full-range-speaker-4-ohm--297-2157. As soon as I got them, I mounted one in a tin can and tested it out. I couldn't believe my ears! The sound this thing makes in such a small form factor is insane! I rebuilt the speaker boxes for them and installed them into them with a filter capacitor at 200hz.
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Also a ton of work was done on the electronics portion. The batteries were wired up to the management boards and the chargers wired to that. I seemed to be having problems with the chargers charging them if left hooked up, so I had to take it apart to charge them. I have recently tried putting diodes in line of the positive of the charger to prevent back flow into the charging circuit. This seems to help, but the chargers still seem to overcharge the cells. Here is a picture of the electronics assembly.
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I know this post covered a lot and a lot of detail was missed, but the log is now caught up and I will update it as soon as work is done on the speaker from now on.
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Re: Omni-Directional BoomBox

Postby Josh Hess » Mon Jan 18, 2016 2:40 am

A quick update, I did a sound test video here:

youtu.be/0ScY756I3Rc
I'm planing on rebuilding the main chassis and doing some minor changes on the electronics next!
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Re: Omni-Directional BoomBox

Postby Josh Hess » Sat Dec 17, 2016 3:06 am

It's been quite a while since I have done anything with this so I decided to finally do some revisions on some things. Firstly, I replaced one of the BMR drivers with a Dayton Audio 3" reference driver which has a richer midrange. I felt the BMR's were a bit lacking in the lower mids. I also designed and have begun building a better reflector as the pyramid design was only supposed to be temporary. Anyway, I will have some pictures as the parts are completed. I also plan to do minor modifications to the electronics and also rebuild the frame so it looks nicer.

Updates to come!
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Re: Omni-Directional BoomBox

Postby Josh Hess » Sun Dec 18, 2016 12:56 am

I finished up the new reflector today and it works great! There is a noticeable improvement in the clarity of the sound especially in the highs. The treble seems less harsh and midrange much more clear. It almost gives it a more open and smooth sound if that makes sense. I was so excited building it, I forgot to take pictures along the way but here are a few:

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