Introduction: How to Build a Cheap, Powered Speaker Box
Intro / Reasoning
I like to repurpose stuff I have lying around. I picked up a 200 Watt AMP for only $20. I also had a bunch of boxes from moving and some Rockford Fosgates I wasn't using and several pc power supply units (PSU hereafter).
I saw another instructable (can't find it right now to link) where someone put together a nice wooden box with some tiny speakers, a PSU and a car radio. I wanted to actually copy that for myself but had trouble getting hold of a head unit to use that was either good enough or cheap enough.
So here it is!! The Jack Daniels Audio Box.
USES KNIVES!! Don't die! Don't bleed.
Be sure to make sure your components all fit the box ahead of time.
This Instructable needs a better name!
Step 1: Installing the Speakers
After I found a .pdf online of the speakers' datasheet I used photoshop to create a printout that was the same size as the speaker. I got lucky in that my datasheet had a picture in it already with the measurements listed.
Once printed I had to decide how to position the speakers.
[This is where I made my first mistake. I chose a place based on the speaker's size but had yet to think about the covers I'd forgotten were out in my trunk. They overhang a bit but its not a big deal. Still, I wish I'd not gone with the straight up & down but an angle setup.]
In the end I chose to install them straight up and down (my speakers are ovals or 6x9) to maintain more box integrity.
Now that I've chosen my positioning I tape down the guide then take my knife perforate along the chosen line. [Be sure to check the lines carefully so you are cutting inside the screw but outside the cone.]
Be sure to stick to the one line all the way around and keep perforating. I found it helped to put a hand in the box to push back. A sharp knife helps, too.
Once you've perforated both sides go ahead and pull off the guides if you need to, but keep them in good shape for marking screw holes later. Start cutting out the holes, preferably with a narrow blade to make the tighter turns with minimal damage.
NOTE: If you care to make the enclosure sealed then your going to want to tape/caulk/hot glue everything right now, plus you'll have to chamber off the AMP & PSU in the end. This box was too small for me to care that much.
Now decide on your attachment method. I chose zipties since I've got a sack of them lying around. If you lack covers that have screwholes you'll have to reinforce the box around your holes.
Attach your speakers. Start on the bottom ones. Don't forget the covers.
NOTE: When in need of more grip on the box or when making sure duct tape is sticking do NOT crush the box. Every place you pinch it flat is a weak spot. It's not like this is built for durability.
Step 2: Installing the AMP
This will vary greatly based on the amp you have. My amp I'm using for my subs it shaped so weird I would never attempt this, but this one has a flat surface to each side except for a removable plate on the bottom that hangs out to the sides where you would mount it normally. I removed the plate but turned it sideways and taped it to the bottom to add some protection against just lying on the bottom of the box with bare components.
Due to the small size of my box I chose to mount the AMP with it's own hole instead of running RCA to a hole in the top. Since I was able to remove the face I taped the face from behind into the hole in the box I'd made for it. I didn't mount it flush because the face is flush with the heat surface. I didn't want that much air exposure so it's recessed a bit.
Before I taped the faceplate down I wrapped the edges of the hole with duct tape for sturdiness. After taping the faceplate into place from behind I put a run of tape across where the screws go so I can put them thru the tape when I reattach the amp to it.
Now you should attach the speaker wires while you still have it loose. (Those forked connectors are really handy.)
I placed the AMP and reattached it to the face. I went ahead and added a little tape to the bottom and on the front corners to help hold it in place.
NOTE: I chose to keep the bottom towards the front and then left a gap in the bottom of the hole where the faceplate is taped on, this gives a more direct current of airflow being sucked in across the components.
Step 3: Installing the PSU
There are quite a few guides on here on turning the PSU into a useable power supply. All you really need to know is the GREEN wire is the "ON switch", as it were, and all you have to do is connect it to the GROUND wires.
For our purposes I've take all the extra wires and twisted them up in groups to make them more out of the way. We only need 4 connections; the GND (black) of course, the + 12 Volt DC (yellow), the - 12 Volt DC (blue) and the GREEN wire. I choose to bundle them together to simulate a larger wire and allow some higher current draw with less heat per wire. (I made 2 GND terminals because I put one on the amp and the other on the switch.)
NOTE: Test your PSU. Tape down exposed wires and put a voltmeter on them to check that your PSU is working.
You'll notice I've placed terminals on all my connections because they fit the switch and the connectors for the AMP.
Now find a place to put it, cut a hole, tape it up, tape the crap outta that thing to keep it in place. I did not cut my hole big enough to push the PSU thru and I was okay with it since it matched the mounting for the AMP.
Be sure to not only tape it up so it won't fall but also so you won't push it in when putting in the plug. Get it taped into place all the way around, be sure to leave the vents as open as you can.
Once you've got it into place go ahead and hook up the AMP connections.
Step 4: Installing the Switch
NOTE: Be sure you're testing you connections as you go at this point. Hopefully you tested your PSU before installing it.
Now the switch. One the switch are three connectors; load, power, GND. GND seems obvious. Load is the power to the light which is the -12V (blue) wire for us. Power will be the green wire. The green wire doesn't really have more than a miniscule amount of power on it, but this gets us connected to the GND.
The types of switches available is huge. I bought mine at the auto store which sometime means they've got a fuse. Good thing? Depends on the size. This amp can pull 16.67 Amps at peak when at 12 V. You can find this info in your manual by finding the peak wattage then dividing by 12 (the voltage you will be running at assuming your PSU is running at optimal voltages). My 200 Watt (2 x 100) AMP can therefore pull (200/12=16.666666....) just under 17 Amps. Some of these switches end to have very small fuses of 10 or 15. Be aware of this at purchase.
Be sure to find one that COMES WITH a mounting connection of some type. Mine is a small screw-type connector, it leaves an awful lot of switch up front but I was determined not to buy anything for this project when I had so much lying around.
The hardest thing here was not deciding where to put my switch, it was cutting a round whole in cardboard. I got my best knife and just worked a small square then rounded it out until I reached the size I needed. I also surrounded the whole with tape and even put a little through that is under the switch where it can't be seen.
TEST YOUR CONNECTIONS!! If everything works you can close her up.
Step 5: The Reason for the Blue Wire?
I experimented for awhile and best I can tell is that you have to use the blue wire because it is the actual 0 Volt connection which means it's the only one that won't short the power suppler when connected to the green wire.
Electricity is weird, if you put a PC fan on the +5 and +12 connections instead of GND and +12 then you'll get the difference in voltage as your power, +7. So we can conclude the the GND or Negative (black) wires are actually +12 and the +12 (yellow) are actually +24. While this may be, the case is grounded on the black wires (i.e. anything connected to black could be connected to the case). Also, the -12 (blue) has very limited amperage available. The +12 (yellow) are the main and have the most current available.
Why does the -12 (blue) wire work then? The difference in voltage affect. What you are really connecting is 0 V (blue) to +12 (black). This means the current is flowing in reverse and that is why I tell you not to use a polarized lighted switch. Although you could easily swap the GND and -12V (blue) wire since when the switch flips it connects to both the other pins.
Step 6: Final Thoughts
Temperature issues? Read captions.
What would I change?
I would put in a connection for hooking it up to my car's power or to a battery for when I'm out & about.
I would suggest an LED to indicate power instead of a lighted switch. This could be on any other power/GND combination without being connected in some way to the GREEN wire and causing the PSU to short out.
A bigger box so I could section off the AMP & PSU and be able to seal the rest of the box. (A taller one at least.)
A box where I could mount both speakers up front.
A volume knob. My Blackberry on its lowest level is too loud to listen too when someone is sleeping in the apartment. I believe part of the problem is this AMP's high impedance input is not very high at all. When I turn up the volume on the phone it becomes fuzzy quickly, but if I turn up the gain knob on the AMP it doesn't get fuzzy.
A smaller fan for the PSU. The full size fan was unnecessary and may be contributing to power loss and noise.
If I had a bigger box I would've mounted a Zune and iPod dock on top plus an RCA connection.
I should have used my better power supply.
Yes. Painting your PSU limits the heat dissipation, but I don't think it'll be a problem.
I wanted to use an auto head unit (radio) but I don't have any extras of those and this amp was cheaper.
We have a be nice policy.
Please be positive and constructive.