Introduction: DIY Stereo Bluetooth Speaker (2x30W)
This is a pretty thorough walk-through of everything you'll need to know to construct a simple Bluetooth speaker with a "first order crossover" (more on that later).
This is my "full" version of the instructable linked below, from which I used the aesthetics and amp. My instructable will fill in all of the blanks, and provide you the details and design understanding you would need not only to produce this speaker, but a speaker of your own design, with parts of your choosing. The below link does not contain enough information to build a speaker, alone.
This guy has a speaker store. He sells speakers, and plans to make speakers. I followed the above instructable and liked the aesthetics, followed the links (which may also be monetized) to see the types of components he used, and then after seeing that the details were omitted (and charged for), immediately researched how to created a speaker on my own. I don't believe that financial motivation belongs in the "building/instructables" community. Particularly the dimensions, design choices, and electronics of my speaker are of course all my own, and this instructable provides much more detail than any other of it's type for someone to create their own, uniquely.
Besides the design method and plan, and a list of all of the tools/calculators/electrical components used, I've included detailed drawings of the cuts of wood I've used. I dimensioned the box based on the actual dimensions of the wood I had so as to avoid making cuts, but you will likely have to customize yours a bit. Also, this speaker is not battery operated, but could easily be upgraded by buying the relevant kits made for the board I used.
Since I knew nothing about speakers before starting this project, I've included (too much) detail regarding the crossover, as well as some fundamental electronics, so feel free to skip over this if you figure yourself advanced.
Step 1: Tools/ Materials
Before getting into the design of the speaker, I'll list all the stuff I used. There are many different amp boards, speaker drivers, and crossover types, but for simplicity, I'll just list what I used and explain what you can change yourself in the relevant section. Throughout, I may use "speaker driver" to mean the familiar cone shaped electronic component that actually makes the sound, just to set it apart from the speaker as a whole (wooden box (cabinet) and all).
-Disposable respirator (routing, cutting, sanding)
-Chemical cartridge respirator (staining)
-Safety glasses (routing, cutting)
-Ear protection (routing, cutting)
-a (sliding compound) mitre saw capable of cutting 1x8" @45 degrees, or a table saw and digital angle gauge (my neighbour helped me out with his table saw, but didn't have a digital gauge, so it took sanding to get a perfect 45, see late)
-a method for cutting the back plywood piece down to the precise size of the front piece (doesn't have to be clean, a jig saw would be fine)
-a router, with either a routing table and a straight bit of basically any size or a rabbeting bit deep enough to cut the depth of your front baffle piece (i.e. the distance from the bearing to the edge of the bit) This creates the channel that the front baffle sits inside. Also a 45 degree chamfer bit for finishing the holes on the front baffle... you could use a roundover bit too, but I prefer the way the chamfer looks
-a drill with lots of bit sizes, particularly big ones for the speaker holes. For the speaker drivers listed below, you need a 3" for the woofers to show through, as they will be mounted on the inside, facing out, and 1.25" for the tweeters, which press fit into place. If you finish these holes anyways, it doesn't matter if they're rough, but a forstner bit would be ideal. I didn't use a drill press because cedar is soft, but with hardwood it might be advisable. Other holes must be drilled for the switches, lights and inputs on the back. Because of the geometry of the inputs/lights/switch, you may need to countersink these holes, which necessitates a forstner bit of between 1" and 2". I personally carved room for mine out with a dremmel, but if you use hardwood, making room for these components will require more forethought.
-(optional) an orbital sander... but it makes it easier!
-(optional) corner clamps
-(optional) hot glue to keep the components and board fixed within the speaker
-(optional but highly recommended) a DMM for checking a handful of things (see later)
-soldering iron and solder
-sandpaper to remove coating from inductor wires (usually red) to expose metal
-masking tape to wrap up the box when gluing
-stain for the box and back panel (I used minwax ebony)
-danish wood for the front baffle (I used Danish oil)
-2 pieces of wire to complete the crossover (connect -ve terminals of speaker drivers). I save mine from changing light fixtures in my house! (copper isn't necessary).
-wire strippers or careful use of a knife/pliers
- ~7-8' of 1x8" pine (or plywood, but I would highly suggest pine) for the box. I used clear (as opposed to knotted)
- ~2' of 1x8" wood that looks nice for the front baffle piece. It can be hardwood, but I used cedar
- Some ~1" plywood for the back panel which will be cut to the exact same size as the front baffle
NOTE: In the U.S., "Parts Express" has the largest selection, and Quebec based "Solen" as a Canadian counterpart. I used Solen but you can find identical components at Parts Express. If you're going to buy parts from Solen besides the ones I've listed here, I would browse on Parts Express and then try to find them on Solen, since their website is a little lame and has few reviews.
-A stereo bluetooth amp - This amp is VERY simple, in the sense that it has cables for functions like a volume knob, aux in, indicator lights, power toggle, and other features are all sold separately, and simply plug in. Because of this simplicity, and the fact that it's Bluetooth, it's expensive.This amp provides 30 W to each of the left and right channels. There are 15 and 50 W varieties, but 30 W is enough for the actual speakers (drivers) I have chosen. You could very easily pick your own amp, and the only things that will change are the power supply requirements (more later) , and the location of the inputs. In the future, I would personally use a cheap, simple amp that had good reviews in terms of quality. The lights are for show, and bluetooth isn't the be-all-end-all given that it wouldn't be portable. You're also paying extra for the boards capacity to easily add battery power. A fun option would be a 2.1 (2 channels and a subwoofer) amp. To prevent confusion, I won't add a link, but you can find a 30W 30W (L&R) +60W (Sub-Woofer) amp for ~$15 dollars, with a DC power jack, red/white RCA input, and volume knobs for each channel fixed onto the back. This could reduce the cost of this project to well under $100.
The bluetooth on this board is known to be a little spotty, so to be safe you need the cable set which provides aux-in, below. My bluetooth works perfectly fine, but I will mention a quick fix suggested by Dayton (the manufacturer of the board) to correct one issue. There is a ground wire grouped with the cables used for the aux-in jack, and I believe Dayton has now removed this wire, but if not, then you should just remove it. See the PDF attached. It is the wire next to the already empty slot. I think this is caused by a "ground loop", where essentially 2 "grounds" are at different potentials. If this occurs when using a different setup, a solution would be to use a "DC-DC isolating converter".
-The "cable packages" I got. The amp comes with cables for the signal out to the speaker, as well as power. The "functional" cable set comes with a volume knob, power on/off toggle cable, aux-in cable, and a battery cable (not used here). The "LED" cable set comes with 3 cables (red, green, blue) to be used for power, bluetooth, and charging indicators. I used 2/3.
-The "woofer" (x2) - This is really what is called a "full range speaker", meaning that it is intended to perform fine in most of the audible frequency range. Feel free to look for another full range speaker. It can have a different "impedence" (more later), diameter, "sensitivity" (more later), or "frequency response" (more later), but keep the "RMS Power (handling)" (more later) in the 30W range, since the amp only provides 30W.
-The "tweeter" (x2) - These little speakers "respond" (more later) to high frequencies better than the full range speaker, and so they will be used to supplement the full range woofer. The same goes for the tweeter as for the woofer in terms of selecting your own, but this specific model has received very high praise.
In addition to the amp and speakers above, simple passive electronic components (inductors, capacitors, and (not for me) resistors), make up what is called the "crossover" (more later, but the gist is that the range of frequencies that make up the music needs to be "split up" between the speaker drivers based on which frequencies that speaker "handles" them better... this will make much more sense later! For example, if you just used a single full range speaker for each of the channels (left and right), then no crossover would be required). There are many different types and values for these components, so although none of them are very expensive, you should take time to ensure you order the right part, or otherwise discuss it with someone at your local electronics store.
-Capacitors (x2) - This will depend on the following steps. The value chosen is for the impedences of speakers drivers I chose above, as well as the "cutoff frequency" (more later) that I selected. I have 2 listed here, since the capacitance I calculated I would need was actually 12.62 nF. The closest sum of 2 capacitors I could get was 12.68. As it turns out, I only ended up using the 12, but I will discuss this later. For capacitors (not inductors), the "polarity" (more later) of the capacitor matters since they need to be put into the circuit facing the right way. There are several different types... at several different price points, but selecting a "non-polar" capacitor will avoid you needing to check which direction the capacitor should face in the circuit. Generally, if it doesn't say "polar" it's not. These components could be picked up from a local electronics store as well. The error on most capacitors is typically +/- 10%, so as a rule of thumb for use here, getting a capacitor (or capacitors) which add up to within this range will be fine. I'll explain how they will be wired together later if you get more than 1.
-Inductor (x2) - The value of these inductors will vary in the same way as the capacitor, with a couple of notes. Firstly, there are a few types of inductors, but you should use an "air coil" inductor (just wire wrapped in a circle a precise # of times to get a desired inductance). You may see the term "litz", which simply means the wire is braided, and for our applications is not necessary. It is supposed to give you better power delivery by minimizing losses due to the tendency for current to be concentrated on the surface of a wire, and does this through increasing the surface area of the wire (splitting it into strands). Solen is a very good place to get inductors (for those at home and abroad alike), since they make their own in house (? solen = solenoid ~ inductor ?). Unlike capacitance, there is no easy way to measure inductance (for spot checking or otherwise), so all the more reason to ensure you get a quality one.
Other electronic stuff that didn't come in the kit
Sourcing these will depend on several factors. For me, for example, Solen doesn't sell knobs, DC power jacks, DC power supplies or switches like Parts Express, so I had to buy these at a local electronics store. You could also use amazon. Note that the cable kit does come with a knob on the "potentiometer" (the electronic component which is the volume knob), but it's a little ugly. The DC power jack is absolutely necessary, and so too is the switch. I've provided links to the local electronic store where I purchased my parts so you can see that they're exactly what I used, as well as Amazon, so you can see that these don't have to be very particular.
DC Power Supply: everything you need to know
A gajillion electronics in your house use a DC power supply, and they are made up of a little box, which converts your sockets AC power to DC power. The power of the supply is of course the voltage output times the current output Power(W)=Voltage(V) * Amperage(A), and all 3 of these things vary from supply to supply. These 3 values will be written on the black adapter box of the power supply.
To understand power, voltage, and amperage in the context of a circuit, consider this analogy. The water pipes leading to your home have a certain pressure, determined by the pumps out of the water treatment plant. If this pressure is too high, the piping in your house may get damaged. This is like voltage in a circuit. Voltage is determined by the power source, and can damage a circuit if it is higher than the components are designed for. If you want more water to flow out of your tap (since you can't increase the pressure), you must open up your faucet. This is analogous to amperage. A circuit requests a certain amperage of the source, and assuming the source has enough power, it will provide it. Ultimately, the amount of water flowing out of your tap is analogous to the power of the circuit. The circuit requires a certain amount of power, just like you might desire a certain flow of water, and to get that given a fixed voltage, or pressure, a circuit draws more amps, and you open your faucet.
Back to circuits, here are some scenarios that will demonstrate whats OK and NOT OK for power supplies. Take as an example a 12V 5A circuit. A 12V 5A power supply would be perfect, but with a...
1) 12V 10A power supply
Perfectly fine! The voltage is not too high so as to damage the circuit, and although the power supply CAN supply 10A for a total of 120W of power, it only has to work half as hard, since the circuit only requests 5.
2) 24V 5A power supply
VERY BAD! The voltage is too high, and may damage the circuit
3) 6V 5A power supply
KINDA BAD! The voltage is too low to provide enough power to the circuit. For a simple circuit like a speaker, it may end up being fine, just quieter than it's possible full potential.
4)12V 2A power supply
KINDA BAD! The voltage is fine, but when the circuit attempts to draw 5A of current, it will push the adapter of the power supply beyond its limits, possibly overheating it in an attempt to supply more amperage and thus power.
For the amp listed above, the recommended power supply is 12-24V and 4A. Theoretically, this means you need a power supply with between 12 and 24V and at least 4A. Practically, however, it's likely that if you had, for example, a 24V*2A power supply, you'd be okay, since the recommendation suggests that the minimum power required by the amp is 12*4=48W, so at 24V (which is within the acceptable voltage range not to damage it), the amp may only draw 2A. I personally used a 19.5V * 2.31A = 45W power supply. The supply is not 4A, and technically doesn't even reach the apparent minimum 48W suggested power. This suggests that the amp does not actually use this much power, and thus draw this much current.
However, despite this working perfectly fine, if you want to be safe, get a power adapter that is between 12-24V and at least 4A. The obvious choice would be the standard 12V*5A. I've linked one below, and I would put money on you having one at home.
Power plugs are composed of metal tube with a pin inside, called the "barrel" and "pin" respectively. This will be important later when talking about polarity, but I'll leave that for now. Plugs and jacks mate male and female and are defined purely by geometry. The most common dimensions are 5.5x2.1mm (the plug on the supply above is this).
If you're gambling on a power supply you have kicking around at home, I would get a 5.5x2.1mm jack (female end).
It is important to understand which contacts on your jack correspond to the contact which will touch the pin, and barrel respectively, in order to match the polarity of the power source with the polarity expected by the amp, so as to avoid damage. I will explain this later, but I thought I would mention it now.
Any knob you like will do. You just pull the rubber head off of the supplied volume knob (officially called a potentiometer) and put yours on with a set screw.
Toggle switch for on/off
There is a power switch that comes soldered onto a toggle cable, but it is an "on,on" switch, and does not work for use as a power on/off switch. Be sure to look carefully to make sure your switch is On/OFF or ON/OFF/ON (off in the middle position), and is NOT MOMENTARY, otherwise it will be spring loaded to the middle position. I made this mistake (see later).
Step 2: Crossover Design
As mentioned earlier, crossovers essentially are the circuitry between the amplifier and the speaker drivers themselves, and serve to split up the range of frequency of the music being played, and have each speaker play the frequency they are best at.
There are many many kinds of crossovers which I won't go over here, but the gist of it is that for each channel (in our case, the amp has 2 channels, each of which plays a distinct track where frequency changes with time to produce music), there must be a closed circuit with at least one speaker (which acts as a resistor, a load) in that circuit. If 2 speakers were, simply placed in parallel with one another, they would receive the same waveforms with the same amplitudes. To limit each speaker to playing only the frequencies they are best suited to play, low-pass and high-pass filters are used. These do just as the name suggests, and let pass either high or low frequencies. The woofer has a low pass applied to it, and the tweeter a high pass. The simplest form of these filters is the application of an inductor and capacitor into the circuit respectively. The value of these are specifically chosen to increase/decrease the amplitude the the voltage (the volume) to the woofer and the tweeter at the same time, so that an even, level "frequency response", with not spotty areas exists. The frequency at which the woofer and tweeter phase into one another as they trade off being quieted or being full-volume is called the "crossover frequency". It is defined as the frequency at which the amplitude has decreased by a factor of sqrt(2), and after that point the amplitude exponentially decreases to 0. This point is selected based off of the frequency response graphs. These graphs are provided with any speaker driver, and show the dB response (volume) at a given power for each frequency in the audible spectrum (to 20Hz-20kHz). For a woofer and tweeter, you can simply find a point before the woofer response gets messy, and after the tweeter has reached full response (becomes level). See the attached images.
For interest's sake, and to refresh my differential equations skills, I've written out a rough derivation of how these filters work, and how we arrive at the simple equations that explain how these passive component values are selected. For those of you that look closely, I of course know that this is for an RC (resistor capacitor) low-pass filter, not an LC (inductor capacitor) low-pass filter, as is used in this crossover. The principals are the same.
Luckily, there exist handy online calculators that will even spit out a circuit diagram for you to follow when soldering.
This website will also teach you about more complex forms of crossovers. In a nutshell, the "order" of the crossover determines how steeply the amplitude drops off once the cutoff frequency is reached, allowing for very distinct transitions between speakers. The "way" (ex. 2 way) is just the number of sections the audible frequency range is being split up. A 3-way would have a true woofer, a mid-range woofer, and a tweeter, each being full-volume for only a segment of the frequency range. There are different styles of crossovers, ours is a butterworth, and it is a 1st order, 2 way. Feel free to make circuit diagrams for other crossover types too. It is in this calculator that the impedence of the speakers you choose comes into play. Impedence is always very clearly stated in the data of a speaker along with the frequency response graph. If you choose different impedence speakers than me, or of course a different cutoff frequency, you will have different inductor/capacitor values. In terms of the power of the speaker driver, it's RMS power should certainly not be more than 30W, given the power of the amp, but does not affect the crossover. Lastly, in terms of the sensitivity of the speaker. This is related to the frequency response of course, and depends on many factors, but is essentially the volume of the speaker at a given power, i.e. how effectively it takes electrical power and delivers it into mechanical power (directly related to the amplitude, i.e. volume). The number given is usually measured with a microphone in dB, 1m away with 1W supplied to the speaker driver. This is a hugely complex topic that can't be summarized simply, but check out this link for some interesting tid-bits.
I've added a couple extra + and - signs, and a re-drawn version of it to emphasize the nature of the circuit. See attached image. Re-creating this circuit is as easy as following the diagram and connecting the positive and negative speaker wires (as labelled on the wiring diagram that comes with the amp) from the amp to the positive and negative points in the diagram. If you haven't done many electronics before, remember that there does not need to actually be wire between connections as in the diagram, this is just to spread things out. For example, a wire can be used to connect the negatives of the tweeter and woofer, then the negative speaker wire can connect to either the negative terminal on the tweeter or the woofer, it doesn't matter since they are all at a junction together. In fact, if you do it right, you should only need 2 pieces of additional wire besides of course the speaker wires which plug into the amp board, and that's between the negative terminals on the woofer and tweeter (1 piece for each channel). The terminals on woofers are labelled, but on tweeters, they sometimes just paint the positive one red. Remember that red always means positive, and black negative.
I will not go into further detail about following the circuit diagram, but I will mention a few logistics about physically soldering, and my notes about the polarity of the power connection later on.
Step 3: The Logistics of Soldering
Soldering, macro-components as you will be here, serves mostly to anchor your connection points so they won't become loose. You should be able to (and just simply should) do a "dry run" of your components to ensure that everything works properly before soldering it together. These are the steps you should follow for this project:
1) Use sandpaper to sand off the insulative coating on the inductors, and expose the copper underneath
2) Use wire strippers or otherwise expose a good chunk of the speaker wires, as well as both ends of the 2 wires used to connect the -ve terminals of the speakers give yourself lots to play with so you can form good mechanical connections prior to soldering
3) Plug the power and speaker cables into the amp board following the diagram provided
4) Isolate only the positive and negative wires of one channel, say left, and tape the other 2 to the table or something
5) Connect via twisting (along their length), the positive speaker wire, and both the capacitor and the inductor, at one end. Ensure that if you got a polarized capacitor that the symbols line up + and -ve... normally arrows point in this direction
6) Connect the other inductor end to the positive terminal of the woofer, and the capacitor to the positive end of the tweeter *NOTE, here, if you had 2 capacitors which sum to your desired total value, put them in parallel, meaning attach head to head and tail to tail, and pretend they're 1. For inductors, put them head to tail, in series. I planned to use 2 capacitors, but upon measuring mine with a multimeter, I noticed one already read very high, so the second would have only added to the error. As you can see, the capacitor I added was ~15% high, as is sometimes typical with new non-polar dielectrics, but this didn't matter. If you haven't got a multimeter, you'll just never know it was wrong.
7) Connect your spare wire between the negative terminals of the woofer and tweeter
8) Connect the negative speaker wire from the amp to either one of the negative speaker terminals, I chose the woofer because there was more room to pass the wire through the eyelet.
FOR THE DC POWER JACK POLARITY!!!
1) Look at the power supply you are using. There is an image of a ball and cup joint, with either the ball or the cup arm labelled with a - or a +. There's a 99% chance that the ball is labelled +, and this corresponds to the PIN on your power plug. This means that you want the terminal on the jack you selected which is connected to the same piece of metal that the pin will touch to be POSITIVE and the other one (which connects to the barrel) to be negative. There are 3 terminals on the jack, 1 will not be relevant to either. The one that is not like the other 2 is likely to be the terminal for the PIN. The closest of the other 2 to that terminal is likely to be for the BARREL. You should connect the positive (red) power wire to the PIN terminal, and the black (negative) power wire to the barrel (if your power supply is pin positive, which is very very likely is). Again, I used a multimeter to check the continuity between the contacts on the female end of the jack and the terminals on the back, but if you can figure it out which is which some other way then it's OK.
Once that's all done, go ahead and plug in the aux-in jack, and then plug it in (carefully) and attempt to play music. If there is sound, it worked... don't worry about the quality. At this point, I should mention that as per the manufacturer instructions, if it hasn't already been removed, you should cut the ground wire on the aux-in pin that goes to the amp board since it causes interference. I believe they now remove this wire, but there is a pdf on the dayton audio website to clarify what I'm saying.
THE TWEETERS PRESS FIT IN FROM THE **FRONT**, SO DO NOT SOLDER THEM UNTIL THE FRONT BAFFLE IS DONE AND THEY'RE PRESSED IN PLACE
If you're comfortable, sure-up all your connections BESIDES THE TWEETERS with solder, being careful with the tweeters, since their terminals are merely embedded in plastic wrapping, which gets soft.
Lastly, test out the whole thing with the toggle switch. Luckily, if you bought an On-Off toggle switch, you've just got to make sure that the 2 adjacent terminals are connected to the on/off cable from the amp. One toggle direction will be on, and the other will be open (off).
Step 4: Building the Box: Cutting & Routing
Woaw, that took a while, and this is the only part most people care about. This is where you can do whatever you want, although there are a couple guidelines
1. Unless you choose to add ports (tubes, not mentioned in the parts list), then the speaker should be relatively air tight (enclosed)
2. You've got to leave room for the speakers to at least point through, if not be mounted through the baffle. In my speaker, I "interior" mounted the woofers, rather than have their faceplate against the front, while the tweeters press fit in (through). The tweeters need precise holes drilled to press fit, (1.25" is perfect), but you've got more wiggle room for the woofers. Remember, you can clean up rough EDGES of a ROUND hole, but if a hole isn't round, there's nothing you can do
3. There has to be enough room for the components to fit inside, including the amp board. There should be plenty of slack in the wires. This is a simple build, but when more inductors are involved, it's important to have then oriented in a particular fashion, but here, just make sure they're very far apart.
I have provided pdfs for my plans. I made them based on measurements I took from my wood, but yours won't be far off. I won't go through how I cut the pieces, or did the rabbeting (cut corners out) of all the boards to leave a recess for the front and back to fit in. Generally though, when using a router, it's best to maker many shallow passes, and do all of the boards at one height and depth, so as to minimize discrepancies between boards from changing the depth of the router. When cutting the 45 degree bevels for the box, make sure this is exactly 45. Get the box square first (by cutting boards to the right length with precise 45's), then you can make room for your front baffle by adjusting how deep you router.
Step 5: Gluing the Box
To glue the box, lay all the pieces out like a jacobs ladder along a straight edge, as if you unfolded a pizza box. The long sides should all be facing up so that you have a smooth surface with the corners meet. Carefully add masking tape along the seams, keeping them tight. You'll obviously want to dry run this to make sure it's right, because the tight-ness of this determines how square your corners will be.
Add wood glue to the 45 degree sections, and fold it up, wrapping one last time along where the edges meet to complete the box. It should be tight enough that you don't even need corner clamps.
Step 6: Front Baffle/ Finishing the Box
For the front baffle, I just drilled the holes using a hole saw (for the 3") and forstner bit for the 1.25", and then used the 45 degree chamfer bit to take progressively more off of the corners of the holes, leaving enough for the heavy speaker to mount soundly on the soft wood, and for the tweeters to press in and fit snugly.
Then, with the orbital sander, sand down any scratches or glue seepage on the box, as well as the whole face of the baffle. Remove sharp edges with sand paper. You can sand down the plywood back panel, but it may be uneven. That's OK, since mine took the stain in a sort of leopard looking print anyways, and nobody really sees it.
Remove all of the sawdust (this is hugely important, and drastically impacts whether the finish looks good or not), and then follow the directions precisely for any products you use. Be aware that stain does not take to wood with any glue or glue residue, so you must make sure all of it's gone.
Step 7: Putting the Components in & Some Finishing Touches
At this point, you can press fit in the tweeters, and mount the woofers from the inside. If you want, you can place speaker fabric, or very light linen/ polyester cloth in front of the woofers. Be sure to pre-drill holes for your wood screws, and ensure they're only half the depth of the wood, so they won't show through the front of the baffle. To pre-drill to a specific depth, mark your drillbit with tape at the specified depth.
For the back panel, you will need to drill holes for the power, toggle, aux in, and 2 lights. They're different sizes, and don't need to be exact, but you will need to countersink or otherwise remove a channel in the "back" (the inside facing) side of the back panel for the components to sit deep enough that they show thread through the other side. This may not be clear here, but when you attempt to mount them you'll see.
Some people may tell you to put some foam or something of the like on the inside (particularly along the back) to fill up some room, and keep the air from "bouncing around" too much... you can do this if you want, and there are no particular rules for this, but I didn't (just like I didn't add port holes), since the diameter of my speakers is relatively low, and so I don't believe it's affected much. You can check out this calculator for fun.
Use hot glue to glue down the inductors and board, the capacitors may hang freely. The last step is to glue in the back panel. In hindsight, I might have added weather stripping and bolt holes/ screws rather than glue, that way I could take it open it up if there was an issue.
Step 8: Done!
Feel free to ask questions in the comments!
The red power light (or green if that's what you chose) will be on any time the board receives power. The blue light will blink any time it is in pairing mode, and be solid when connected to bluetooth, as in the picture above. It goes by the "call sign", DAKAB, and will leave pairing mode in preference of aux-in if something is plugged in.