I wish to get a basic speaker preferably from a local store. Are there ways to use components to adjust the resistance of the speakers, or will this just simply not work? I need something that is at most 4-ohm.
If I get a speaker that already has an amp, USB, and all those types of things, can you like pull out the speaker and use a resistor in parallel if it turns out to be 8 ohms?
For more info I think they don't usually state the resistance of the speaker. They state other stuff but dont always give you what you need.
You could but half of the power going to the speaker will be wasted as heat from the parallel resistor. If you need a 4 ohm speaker it's best to buy a 4 ohm speaker
You mean from amazon or something. I prefer to get stuffs from the locals. Does that heat loss really mean anything much on a basic testing project though. I will probably do something different when the time comes to something more serious. I got money to waste. If it did it more serious I would use other stuff.
I can keep whatever I get for future stuff mate. But just for now I want to get something quick.
That's up to you. If the device driving the speaker outputs 1W of power then 0.5W will be wasted as heat and the speaker will only be half as loud.
So you will need a 1W 8 ohm resistor to put in parallel. If you consider the cost of the resistor are you saving money?
Should have something like that around already. I got heaps of other stuff around here. Bit of a mess though. Don't think I will have a problem finding the resistor bits even if I need to put more in parallel. I'm ok with the maths. Got heaps of stuff, just not a lot of speakers, if you know what I mean.
Yes. I cannibalize everything before it goes in the trash, so I do have several little 8 ohm speakers. I think most are from old computers.
You been a top bloke mate.
Have fun!
lower than 4 ohms is closer to a short circuit. higher than 4 ohms would draw less current. are you sure you understand Ohms law?
If the speaker already has an amp, that’s a pretty ideal case - it’s much easier to match the arduino outputs to the input requirements of an amp, than it is to match them to a bare speaker.
Any of the speakers that used to be sold to plug your iPod into should work fine, from the cheap crappy ones to the high-priced better ones. Same for the external speakers for talking to your desktop. A lot of those are selling cheap now that iPhones don’t have audio jack, and desktops get connected to monitors with cables that include sound.
I did not seen an Arduino mentioned anywhere 
I don't think that OP's project involves an Arduino. 5 V / 4 Ohm = 1.25 A, Arduino will not survive that 
Or find 2 8 ohm speakers...
Well, it IS an arduino forum. I assumed arduino outputs, or one of the various sound peripherals frequently connected to Arduinos.
I need something that is at most 4-ohm.
OTOH "less than 4 ohms" is a pretty unusual requirement. Any details of what we're actually dealing with?
Low-impedance (it's not exactly a resistance) speakers would normally be used for very high-power setups, which is ... fiddly to hack together with improvised parts.
You could connect two (or more) 8-ohm speakers in parallel...
The minimum load for a regular Arduino is 125 Ohms (40mA at 5V). It can overheat and burn-up with a 4 or 8-Ohm speaker.
If you have an amplifier you can get raw speakers from any electronics supplier.
An analog "powered computer speaker" is perfect if you don't have an amp for 4 or 8-Ohm speakers. You can get them fairly cheap like this or you can get more expensive hi-fi or gaming speakers, etc.
The 5V or 3V peak-to-peak output from an Arduino is a slightly "hot" line level signal (like comes out of a soundcard or CD player, etc.) and as long as the speakers have a volume control you can turn them down.
It's a good idea to put a capacitor in series with the signal (0.1uF or 1uf) to block the DC component. As you may know, a regular audio signal is AC and it swings positive and negative. The "output" from a series capacitor will do that. Most amplifiers (built into the speaker, in this case) have a capacitor on the input but you can't be sure what's inside.
Is there some reason you can't reuse a speaker from some old non-working device? That is where all my speakers came from.
Hi, @tazman-tinny
Welcome to the forum.
Can I suggest you Google;
mini amplifier kits
These kits will not load your Arduino output down and you will have a convenient volume control.
Just check on what power supply they need.
For example;
Tom.... 
But posted in General Electronics whose title implies that it covers about anything from simple resistor networks to full blown class A valve amplifiers 
Can I clarify something?
You want to get a bare 4 ohm speaker - what do you intend to do with it? You cant connect it directly to an arduino, so you will need to add an amplifier; and you will need a psu for the amplifier ....
Use a computer speaker / amplifier unit and its all there so why would you want to just pull the speaker out?