In this instructable, I'm going to talk about building speakers.

Supplies

To make a speaker, you need at least:

Some speakers (duh)

parts-express.com is a great place to buy speakers or other audio components.
the speakers I bought cost around $23
(more elaboration soon)

an amplifier

you can get one that also has a bluetooth receiver
mine was $15 off amazon, but I don't really like it. Again, I would recommend parts express.
If you just want to hook up your speakers to a a/v receiver or something that already has an amp, you don't need one of these
or you could make your own (look on the internet for schematics, and for buying the parts I would recommend tubesandmore.com or guitarpedalparts.com, but you can use anywhere that works for you.
(more elaboration soon)

a bluetooth receiver

this is optional, only needed if you want it and your amp doesn't already have it.
this one seems okay from Amazon. It has aux in and bluetooth. (see diagram). You have to soldier wires from it to plug it into your amp, so if you don't have a soldiering iron, add this to your parts express order (just read up on how to use it).

crossovers?

I don't really know much about these. I do know that they are mostly used in 3-way or 2-way speaker designs, where you have one tweeter that makes the higher sounds and a driver that makes the mids and a woofer that makes the low sounds. They seem to be kind of expensive and I can't guide you on how to use them, but if you really want a 3-way speaker design you should do some research about these.

a box

in my opinion, this is the hardest part to find. I'm trying to laser cut one, but I know that lots of people don't have access to a laser cutter. (I don't really either, and I'm trying to get access).
https://en.makercase.com/#/ is good for lasercutting boxes. You can put in the dimensions there, get the schematics, and edit them in Adobe Illustrator.

a power supply

your amplifier is going to ask for something like a 24v power supply. I would just look on amazon for something that matches how much power your amp needs and just buy the cheapest one you can find.

That's really all that you need.

Step 1: Note

If you need parts, I would look at goodwill or craigslist or something. I have a subwoofer driver that I literally found by the side of the road. Before you spend money, see if you can get stuff for free.

Step 2: About Amps

What amp you pick is going to determine the whole rest of your project. If you get one without a bluetooth receiver, you're gonna have to buy a bluetooth receiver. If you have one with a subwoofer output, that's nice. If you have one that has big stinky power, that's nice also. If you have one that doesn't have big stinky power, that's less nice (but also less difficult for you wallet).

If you want your speaker to be nice and loud, you probably want an amp that outputs about 60 to 100 watts. (watts is basically how loud it is.) If you want to just make a really cheap little one, just as a test run or something, pick one that's 10w or 5w or something.

Keep in mind that you will need a power supply. Most amps don't come with a power supply, and you're going to have to find your own, which can be a pain. Basically just pick the cheapest one off amazon that is the right voltage. And pay attention to the type of plug.

Step 3: About Drivers

First, we're going to talk about what speakers you want to buy. There are a few things you need to consider when picking speakers.

The first is wattage, which is basically how loud it is. The higher the number, the louder the speaker can go (if you have an amp that can push it that far. Basically, it doesn't matter if you have a 100w speaker if you have a 20w amp, it'll only be able to go as loud as 20w) 60w is probably good for a nice, loud speaker, but you could do less if you want. Try and buy speakers that match your amp in wattage.

Then there's ohms. You probably want around 4Ω or 8Ω, but 16 also works. The more ohms, the quieter the speaker is. So a 60w 4Ω speaker is louder than a 60w 16Ω speaker. There's some weird stuff about ohms but you should be fine if you just have one speaker for the right channel, and another one for the left. It only gets weird when you try and have multiple drivers for one channel (channel being right/left/sub). If your amplifier has a subwoofer output, I would buy one with wattage to match the output.

For the left and right, you want to buy speakers that are "full range," with a frequency response somewhere in the neighborhood of 50 to 20,000 hz.

For the sub, if it says "woofer" you should be fine, just make sure the low end's around 30hz-50hz or so.

Step 4: Put It All Together

Plug your speakers into your amp. I would use alligator clips or crimp terminals or something. If you don't have any buy em on amazon. Plug the amp into the power supply, smash some music thru the amp, and listen to some music!