I'm turning it into a Neo Geo wired for stereo. There was one speaker in the cabinet when I got it, looks like a 4x4 maybe. The one I ordered is a 6x9. This should be ok? I guess the sound might be a little lopsided.
Ok, unless your Neo Geo came as stereo (I dont own one, so I dont know) technically you are not wiring it "stereo". Really you are wiring 2 mono speakers. Wiring two speakers alone does not make it stereo, and wiring only one mono. The difference between mono & stereo is that mono plays all sounds with no technical abilities. Stereo means that it is a "smart" system with technical capabilities. For example, lets say you have a left and right speaker set up for stereo. If a man walking down a hall from right to left came through your stereo setup, you'd hear the gradual loudness and fading of his foot steps start from the right speaker, and fade to the left speaker which would gradually get louder. If you have a mono setup, all you would hear is the sound coming out the same, no matter how many speakers you have. I think your neo geo is not capable of stereo. Instead you will have 2 speakers at mono, which is fine ( I have that in my dynamo and it sounds more balanced than just 1 center speaker).
In regards to the lop sided sound, in terms of volume it will be the same. However the quality might sound different. The shape of the driver (the cone part) is what pushes air through a series of pulsing vibrations to give you your sound. The shape of the drivers will push different amts of air, in your case it would be minor, and you would not hear much of a difference. If you do hear a difference, i'm guessing the 6x9 may be more bassy (deep rumble) than the 4x4 because of it's ability to push more air.
Just make sure it's shielded.
The tard that owned my Dynamo cabinet before me put an unshielded one in and it's messed up the picture on the monitor.
What demogo is referring to is shielded or foiled wire. That means there is a layer of foil or some other reflective material on top of the black and red wire to stop outside interference from messing with other electrical components. For example, if you have un-sheilded or non-foiled wire, the current in the speaker wire may pick up or send out signals, resulting in speaker distortion/crackling, monitor picture shaking, humming or buzzing. Were you ever near audio speakers and heard distortion (kind of like a modem sound) about 2 seconds before your cell phone rings? That's what happens with un-foiled wire.
You can identify foiled wire by the following.
You have the outer jacket (out most part of the wire). Now cut the outer jacket open. Inside you will have a 2 wires (typically red and black or white and black). Those 2 colored wires will be wrapped entirely in what looks like aluminum foil. You'd have to peel that foil back like a banana, and inside you'll have your 2 color wires. Unshielded or non foiled wire lacks that foil barrier.
"modessitt" is correct. It is the MAX power (watts) the speaker can handle before the speaker will start to become damaged. If you want you could put a 100 watt speaker in there. It would just be a waste of money as your amplifier can't put near that much power out.
So... in the end it doesn't matter what size or wattage speaker you put in, as long as it is 8 ohm's and fits in the cabinet (and I think that ohms isn't even really that important, if using a 4 ohm speakers your current to the speaker would just be double, I think home audio is usually 8 ohms, and car audio is 4 ohms).
Right. Think of wattage as your reservoir amt before spilling over and causing a problem. On a mono system (stereo is a bit different, and i'll talk about that later if you want in this example) if the speaker is rated for 10 watts, and the most the amp on the game can put out is 6, then you have a safety buffer of 4 watts left over. You only have a problem if the amp puts out more watts than the rating of the speaker. For example if you have the amp pumping out 10 watts and the speaker is rated for 8, then you went over your limit by 2, and the speaker will distort and blow in a matter of time.
If you install a second speaker, you may have to raise the volume because now your amp has to divide up the power to feed 2 speakers. For example if you have a 5 amp game and 2 10watt speakers, now the amp has to divide up the power, so it becomes 2.5 watts for each speaker which is half the power and volume.
If you have a single 8ohm speaker set up now, you can do one of 2 things (Common Solution)
1) You can wire 2 4ohm speakers together in "series" which will give you your required 8ohms. Wiring in "series" is like leap frogging your wires from one speaker to the next.
2) You can wire 2 8ohm speakers together in "series" for a total of 16ohms. It's a 2 times the ohms, but half the "power". Only thing is you may have to turn up your volume a tad.
Your goal is to not go below 8 ohms. That's getting into the danger zone which could happen if you wire in parallel instead of series for this example.
As a beginner do not wire in PARALLEL! Make sure it's in SERIES!
You can see how simple "series" looks in google images. Just search "speakers in series" under google images. You can also see what parallel looks like which is what you don't want.
Is your brain fried yet?

Take a break and read this again in 10 minutes if you still need to.
I'll be on still tonight or later tomorrow evening if you need more help.