PC Bluetooth Speaker

This is my latest little PC speaker project. But my first published.

For me, working in a project like this is not only for the end result, wich is fantastic, but also the whole process is part of the fun, so if you plan on doing something like this, please take it with a grain of salt. You cannot pretend to obtain perfect results if you go like a train and focus all your energy in acomplishing it step by step. I have very limited time left in my life for this projects, so I take it like playing a game. You also don't have every day the same interest in working the same part again and again, so some days I work a little with the wiring, or some other day I work with the drilling, or polishing, etc, etc. The only thing important is to avoid getting bored in the middle of the process, otherwise you would never get to the end.

I spent like four months collecting all the parts, waiting for them to arrive from ebay. So, with everything finally at hand, this project took me about a couple of months, because I took it very slowly, deciding each step very carefully and planning all with dedication. It's like playing chess, but in the end you get something useful that will give you many years of enjoyment, not just a waste of time.

Of course if you count the parts it is much more expensive thant buying one ready made, but as a maker the real heart of the matter is building something that once finished you cannot purchase anywhere, because the end result is so impressive that you cannot just go and get one on the market.

This one was not ment to be wireless, rechargable, (that's my next project) but simply a little speaker that you can power from the USB port and connect to the the line out of the Desktop PC.

This version has bluetooth integrated, so that you can also hear a video from the cell phone for example, with great sound. At first I had only included de bluetooth connect button, but I later discovered that the bluetooth had a low start up volume, so I had to include the volume control (up and down) push-buttons, wich only work for the bluetooth signal path. The line in does not need extra volume, it is already at top.

List of materials:

This is the list of parts that I joined together to make this little project.

I list the original Ebay descriptions, so you can look for them right away.

Hammond Box 1590G Aluminum Box (taller than the original 1590B).

PAM8403 Bluetooth 4.0 Receiver Board Stereo Digital Audio Amplifier USB CSR8635

2pcs 40mm 5W~10W Full-frequency bass Bluetooth wifi Speaker neodymium hifi. (this is just the description, they are simply drivers, not bluetooth of course, the bluetooth capacity is in the amplifier board).

Passive Radiator 105 x 60 mm.

5PCS 12X12X7.3 Tactile Push Button Switch Momentary Tact LED 5 color

White Angel Eye LED SPDT 16mm Thread Self-Locking Metal Power Pushbutton Switch, (12 Volt version). Lights just perfect with 5 Volts.

Flexible Soft Silicone Wire RC Cable : It comes in different gauges from AWG 26.

A hint:
After years of electronic projects I finally decided to move from regular cable to silicon rubber cable, from the new trend of diy quadcopters and RCs, now it is very easy to find it, and much easier to use. First: their inner strands are finer and more flexible than regular cable, so it better handles bends and torsion. SecondIt: is very easy to trip the cover and third: it resists much better the heat from the soldering iron, so you work more relaxed with a much better end result. I finally ended up purchasing a variety of gauges in a couple of meters each and it will give me a lot of relieve from painful tinning and soldering processes. The little cables I soldered to the original push-button was a regular cable and It took me a lot of effort doign it for the cable insulation easily melted during the soldering operation. And the cable finally ends burnt and brittle, so I had to apply some glue to it to hold it firmly to the board.

mini xlr 4P 4 pin female Audio Mic connector TA4F

Male Plug Mini XLR 4 Pin Audio Microphone Chassis Mount Connector

40pcs 9mm DIA Effect Pedal AMPLIFIER RUBBER FEET MAT PAD STAND

Of course there are things that can be ommited completely, for example the cable connector for the Power and Line Input. You can just pass the cable in thrugh a hole. The lighted buttons could be replaced for general tactile buttons. The main power switch could be completely avoided and just let the speaker power up on PC boot up.

The speaker drivers I would not change, because this is my third little speaker and this small drivers deliver a sound quality that is quite amazing for the size. A Little expensive but it's worth it hands down.

The Passive bass driver is a must!

Aluminum Mounting Ring: This one I made on my little Proxxon lathe. If you cannot make it yourself maybe you can ask a machinist to make a couple for you.

A good quality USB cable 1.5 Meter.

List of Tools: First of all, during all my projects I wear ear protection and protection glasses.

A pair of files: 25 mm flat profile and 8mm round shape.

To cut the big holes for the speakers on the aluminum box front, you can first draw the circle with a compass and use a rotary tool and make a lot of little holes, maybe 3mm each to outline the big hole for the speaker and then trim the borders with the little sanding drum. You can purchase a lot of this little sanding drums for very little money on ebay. A much easier way is to have a dedicated hole saw. It is an amazing tool because it can cut a big hole in aluminum this thick (2mm) in a couple of minutes at very low speed with a cordless drill.

You may also need a cutting disc for the rotary tool to cut the big mounting hole in the back (case cover side). It can also be done with a little saw.

Step Drills: This drills are used to make the holes for the input connector and the push buttons.

Some kind of elastic glue, like E600 or similar.

Buffing whell mounted on a grinder

Sandpaper 180 grit

Soldering iron 25 watt and solder with flux.

Strong Scissors

A digital caliper is very helpful for measuring, estimating correct diameters and trimming holes.

This amplifier has a little limitation: the bluetooth only works with 5 Volts of power supply, so it is not possible to use it right away with a single Li-Ion Battery, then for such a small box you do not have enough space to accomodate all the extra electronics and batteries needed to operate it with 5 volts with this simple circuit. So there goes my next project.

In order to save some internal space I removed the white speaker connector, first by cutting the connector cables to the pcb, then desoldering the lateral tabs that go to ground, helping to secure the connector in place. Finally I desoldered the remaining connector pins from the pcb. This procedure avoids to apply too much heat to the pcb desoldering the whole connector at once. Then you clean the original solder pads with some flux and new solder.

Removing the micro USB connector:

For the same reason, if you look at the way the Board was placed inside the case, it was mandatory to also remove the micro USB connector. Inserting a regular micro USB plug was impossible because of the lack of space available.

I am so sorry that while making this project I had not envisioned to publish it on Instructables, so I didn't take all the detailed photos I need to fully explain all this. In this bad photo (because the board was already in a heat shrink tubbing) you can grasp how I wired the speakers and the power red and black wires around where the USB connector was originaly located.

The detailed image shows how I soldered a couple of wires in parallel
to the original pushbuttons in order to have acces to them from the new lighted push-buttons. The same was made for the three push buttons. There also appears the location where the board has three pre tinned holes to connect the line input, wich originaly lacks a propper connector. Here I attach the line input audio cable. The earth cable is not needed for is the same as power ground, so they are shared. Later on the connector install I will explain further.

Next I added the extra thin wires to connect all the push-buttons with the external LED lit push-buttons.

The blue LED of the board that indicates bluetooth activity was removed and that solder pads where wired to the blue LED external push-button. The resistor needed is already on the board, so it is a simple wiring to the led.

For the other two push-buttons, volume-up (Red) and volume-down (Green), I had to wire a thin wire to +Vcc and place a little 1/8 resistor in series with each push-button LED (5K). The other wire goes to ground.

Next, the push-button switches get wired in parallel to the original ones, that's all.

The real tricky part is to install the push-buttons on the case and get an AIR TIGHT fit. This is done at the final assembly stage, by a very careful drilling and later filing by hand to get the tight fit on the hole. The push-buttons get glued on its location and at last I carefully covered all the back of the push-buttons with the same E6000 glue, like a painting.

I replaced the original Pam8403 with a much better PAM 8406, wich is pin compatible, but if you lack a hot air rework tool you can avoid this step. The worst drawback of the PAM 8403 is that on strong music transients it just shuts down and re-starts with a very nasty pop. The only way to avoid it, is supplying it with lots of amperes, wich obviously cannot be done through an USB port. I purchased a 1 dollar PAM 8406 board on ebay and just took it from there and re-installed it on the main amplifier board. A little effort makes a big difference in performance.

The use of a passive bass radiator is a must if you expect to get some resonable amount of bass response in such a small speaker enclosure. This is not a speaker enclosure design instructable, so I am not going to get into the details, but as a general rule, a bass port in a box so small like this is completely useless. But on the contrary, a well sealed box this size with a generous passive bass radiator works wonders!!!

I have used other passive drivers in several proyects, like the second photo here, but although they seem ok, they have a lower quality design, the metal plate is magnetic, and the rubber suspension is not so elastic, so they do not work so well. So try to find one that looks like the one used in this speaker, 105x60 mm.

The first time I tried this speaker it was not so good at all. I had made several mistakes:

The most important thing in a passive radiator design: The box MUST BE AIR TIGHT.

Any leak of air makes the system a lot less efficient.

So I had to dissasemble it and re-seal all the switches from the back and re-seal the speakers from the back with a syringe with a thick Nº14 needle and 2" of 2mm heat shrink tube to extend the needle and glue E6000, looking for any spots where the original gluing was not perfect. Also the input connector and the main power switch had to be completely sealed from the back to get a really sealed enclosure.

Finally when closing the door...I had to seal all the back cover with silicone glue to geat a real good seal, otherwise all the previous work is useless.

The second amazing thing about passive radiators: In order to couple with the bass frequencies, it makes a big big difference if the moving diaphragm has some mass or not.

The passive bass radiator consist of four parts:

First I removed the metal frame wich is not needed and is so big that it does not fit the enclosure.

You have to detach it very carefully from the metal frame, but the good thing is the adhesive used is not so hard.

Second, the rubber suspension, wich is the real useful part of the hole thing, has a black flat plate made of thick cardboard, with a metal weight in the middle, to add some mass to the diaphragm.

The problem is that this metal weigth is magnetic, so it gets atracted to the magnets of the speakers, because the speakers are so close to it. So it also needs to be removed. With an exacto knife y managed to peal it from the cardboard plate.

A comment regarding the original design: Passive Radiator MASS

When I first tried this bass radiator without the wheight attached, it barely moved, it was lifeless.

Then I found some round non magnetic steel pieces that I used for adding weight to the system, some 60 grams in total, and voila!!! The bass radiator took life and made it's trick!!!! So without a weight, it does not work at all.

So I ended with this weird passive bass radiator, with four little weights glued on the back, located so that they do not get in touch with the speaker structures. It works wonders!!! On the other hand, the same speaker without a passive bass radiator sounds very very small in comparison. So this factor is key to the whole sound quality.

Next time I will completely replace the cardboard plate for a copper or brass plate.

This speakers have a wonderful sound quality and a bass response absolutely amazing for the size, so much that if you do not mount them in a propper enclosure, you will probably never get it's full potential. I am baffled how everyone demonstrates speakers on youtube simply standing on it's magnet, it is like triying how a car runs inside the garage.

This little drivers have a square frame with four mounting holes, but as I just glued them to the case, I simply cut the outer edge all around with a set of strong scissors, just like cutting sheet metal, until I got a circle.

To be able to install this drivers in a box so small ,you must find a way to extend the mounting point a little forward on the front of the box, in this case I took the speakers 5mm further outside the front of the box, because althought the speakers get mounted from the outside of the box towards the back (the border of the speakers gets on the ouside of the case), there is too little space to allow for the bass radiator to freely move behind the speakers if you do not move them a little further to the front. As I already have a small lathe available, It was relatively simple to make a couple of aluminum mounting rings.

This round mounting frame, serves three purposes actually: one is to slide the drivers further outside the front of the case and also provides a clean finish for the border of the opening of the case, hiding the imperfections of the curve and the edge of the drivers. And third, It provides some protection for the drivers if you happen to drop the speaker face down.

If you own a 3D printer it would be pretty straightforward to design and make a mounting ring that serves the same purpose. Even more, years ago while I didn't have a lathe, I used to ask a machinist to make custom parts for me, the thing is to get the project done.

Here I attach PDF drawings of the rings Top and Front view.

By far the hardest part of the whole project is working the aluminum box.
Just because you need a little extra force to work things out, andyou will also need a place to work where you will make some noise with the tools and will spray a lot of aluminum dust.

First part of the box: Drilling the Holes, big ones go first

The most difficult part is drilling the big opening on the back plate, (back cover of the enclosure). This opening will accomodate the passive bass radiator driver.

For this I have used an electric saw before, but this time I picked the dremel with a rotary cutting wheel. I ended using five cutting wheels, for they go like butter, but I purchased a lot on ebay at a very low price.

Then I trimmed the borders with a 1 inch flat file. And the round 8mm file for the corners. It Took me a couple of hours to get it done.

The holes for the speakers could be done by drawing a circle with a compass and then drilling a lot of 3mm holes all around and then cut in between and trim the whole thing with the round sanding drums, it takes time but can give good results, I have done it before.

Just recently I decided to get a circular saw of the correct diameter and now I can drill the hole at once, with a simple cordless drill at low speed, in two minutes. Then you trim the borders with the little sanding drum. So you go from a couple of hours to five minutes according to the method or tools used.

Once you have located the position of the speakers and you can try how they fit, then you can decide where to place all the other componnents, like connector, switches and the like.

I always use the digital caliper to verify which diameter I will need to drill for each component of course.

For the smaller holes the easiest way is to use step drills, there is no better tool for that job. Simple, clean results.

This kind of aluminum boxes are very sturdy cast aluminum. The only problem is that they exhibit a lot of surface imperfections due to the cast processing. The original finish is awful, so you have to work somehow to get a better surface finish. My aim was to get a mirrof finish. I have made another similar little speaker but in that case I used a simple sanded finish, with the electric rotary sander, that looks fine, but not that beautiful.

In various similar projects where I have used this aluminum boxes before, I have worked with an electric rotary sander. But, in this last one I applied a different approach. In this case I was working late in the night, so I needed a way to sand without making so much noise, so... I sanded moving the box by hand over a sheet of 180 grit wet sandpaper, the kind used for metal. The sandpaper was fixed on the table with double sided adhesive tape. I have used the regular black kind of sandpaper before, but this time I tried a silicon carbide type, wich is gray color and gives a much more uniform finish. It took me a surprisingly short amount of time to get a very smoth finish. In other ocasions I was increasing the grade of the sandpaper from 100 to 200 to 400 to 1200 in steps, to get a finer and finer finish. This time I used a very straight approach: 180 grit sandpaper until a uniform finish and then directly to the next step.

I used to resort to so many stages to get a good finish, but this is a tool that gives fantastic results for the final surface finish in a very short and simple step.

An hour and a half of posishing with some kind of Abrasive Buffing Polishing Compound (Paste Wax Bar) over the buffing wheel and the finish is superb. But you need to use rubber gloves and work gloves to protect your hands from the dirt and the heat that builds up on the aluminum box while you are holding it. The polishing compound melts with the heat, leaving a black lining, that needs to be wiped off.

The cleaning of the residue is done with some soft paper towel, that's all.

I used this kind of mini XLR 4 pin jack connector that allows you to easily detach the cable when carrying the speaker.

As this speaker gets its power supply from the USB port, Y managed to make a special cable where two conductors (Red and Black) go to the USB port for Vcc and Ground, and the other two end up in a 3,5mm stereo mini-plug.

That way you don't need separate cables for power and audio.

I could have installed a USB audio interface inside the speaker, but the problem is that each time you take the speaker to a different PC, you would have to install drivers for that interface before being able to use it, just a lot of hassle.

You need to make a dual (Y) end cable, Power from USB, line in from the line out of the PC.

For the input cable I chose a good quality USB cable and cut 20 cmt of the micro usb end, and 15 cmt. of the USB B male end of the same cable, to make de plug end.

Then you can use a pencil cap or some kind of mini enclosure to tie the three cable ends making a Y cable. So you end up with a USB tied to a mini Plug in one end. On the other end you connect the mini XLR female Plug.

I filled the inside the capsule where you tie all the cables together with epoxy.

Once the box was finished, then I wired, installed and sealed the main switch and the input connector.

The amplifier was fully wired, and placed inside a snug fit heat shring tube.

Then the push-buttons were glued on and carefully sealed from behind, with the same adhesive E6000.

Once all the connections, but the speaker wires, were ready, I installed the speakers, gluing them carefully all around, and later, once dry, I re-sealed them once more from behind, to avoid air leaks.

At last the speaker wires were soldered

Then, to close the back plate I used a syringe with Nº14 needle (2 mm or so) to make a seal all around the frame of the box with silicone compound.

Finally the rubber feet that are self sticking, the easiest part of all.

Once I made the first tests, I discovered that some of the push-buttons rattled with the sound pressure, so I had to carefully remove the color button taking it from the side with an exacto knife and sliding it out, and then placed a very small bit of silicone rubber around the LED to make like a cushion behind the button, so that it gets firm in it's place, without rattling.

My sound quality expectations were low.

I had already made the speaker shown on step 14, wich gave me (I believed) a good sound quality.

So when I finally managed to get this one really sealed, and tried it, my impression was astonishing.

Mainly because it is very hard to believe that such a small kind of driver could possibly deliver such a solid and deep bass response. First I only made tests with drum tracks, but later I discovered that it also exhibits reasonable clarity and an overall balanced sound quality, that is very very hard to obtain in much bigger sound systems.

So, as the minimal expression of a PC speaker, this one, for me, delivers more than enough.

Of course you cannot expect big sound output with 3 watts, but you can fill the room with solid, clear and articulated sound. Now, if you want to monitor a soundtrack, place it in front of your nose and you get really amazed. The passive bass driver makes the whole system jump.