Q: Will an Airport Express G slow my N network down?

1. If I connect the G unit will it slow down my whole N network?

Yes, any non-"n" devices that are connected AND active on an "n" network will reduce the overall bandwidth available to "n" clients.

2. How can you tell which are the G and which are the N Airport Express units? I don't see anything on them distinguishing them.

The "g" Express is Model# A1084 / Part# M9470LL/A; the "n" Express is Model# A1264 / Part# MB321LL/A. These should be printed on the label on one of the AirPort's sides.

Of course everything Tesserax said is correct. But, I have an Airport Extreme "N", two Airport Express "G" and Apple TV2. I can play music from my Desktop iTunes, stream it to both Airport Express and Apple TV2 without any streaming issues. So based on that, I would not hesitate to use you G units.

I think another way to ask the question would be does connecting the "G" units to the Airport Extreme "N" network, diminish the range of the WiFi.

ok... i am going to try to answer this, even though some people dont think i should be answering comments(so please pardon me if everything in here is not correct)... The only airport extreme that is strictly just G (or 54 Mbps) is the (second gen airport extreme router that  looks like the one in this picture of being to the far right. The photo is here . This unit was either grey(first gen spaceship) or white (second gen spaceship) and looked like a space ship. The next router or airport extreme that came out was totally redisigned and looke very flat and rectagular. It is the first one on the left of the picture in the link just above. This first generation of the revamped unit is very popular and has gone through several revisons, but they all kept the basic flat and rectangular shape regardless if it was an airport extreme or a time capsule. These flat rectangular airport extremes were also G routers but these were also N routers and were also interoperable with Wi-Fi Certified 802.11a, 802.11b, 802.11g, or 802.11n enabled Mac computers, iPad, iPhone, iPod touch, and Windows-based PCs. Now lets say you have a router but it is using the 2.4 Ghrtz Spectrum that means it is able to use  802.11a, 802.11b, and 802.11g (and maybe also 802.11n) networks. The router only becomes an N router if you change the setting to 5.4 GHrtz or if was able to auto adjust.  However if you change it to a N only router, that means that you are only using the 5.4Ghrtz spectrum and are not using or sharing the other specturms or radio frequency. While a router is using the 2.4 Ghrtz spectrum, it is sharing or moving between the 802.11a, 802.11b, 802.11g (and maybe the 802.11n) spectrums. There is a lot of advantages to being in the 2.4 Ghrtz spectrum, because many many wifi devices are compatible with it because it is able to bounce between a/b/g (and maybe n). Here is where it gets more tricky, the airport express (the smallest unit) was originally (first gen) only a 802.11g (54 Mbps); only as newer revisions of the airport express came out did it became available to work in the 2.4Ghrz (a/b/g and maybe n) range as well as the 5.4Ghrz (n only) range. If you set your primary router to 2.4 Ghrtz, you will be able to use those two airport express to extend, the internet or listen to itunes on your speakers in another room (as long as it is not the first gen airport express which is 54 Mbps or strictly only G. This first gen airport express is only available for sharing audio with speakers in another room, or acting as a print server - not for extending the internet); the newer airport expresses are a/b/g and maybe n compatible are are able to send audio to another room, act as a print server, and most popular, extend the network if needed. Now lets say you set up your primary router to be 5.4 Ghtz only you might not be able to use those airport expresses. (you will deffinitely not be able to use them if they are the first gen airport expresses - because those were strictly G).

ok, presumming you are using newer units both of the airport expresses and the airport extremes (or timecapsules) then you should be able to extend the network, and the degregation will not even be noticible. It will reduce the bandwith some, but hardly noticable.

If your airport extreme has a firmware version of 7.6.0 or higher you have a newer (but not necessarily the latest) router and these units are N compatible in the 5.4 Ghrtz spectrum as well as 2.4 Ghrtz spectrum (a/b/g and maybe n). If you have an airport express of firmware version 6.3 or less; yours is a first gen airport express and will not be able to connect to your network using airport utility 7.6.1 (asuming you have installed it.) 

If you are able to pull up all the routers using airport utility 7.6.1 (before or after resetting the routers) - you will be fine to use those airport express with that current router.

set up the primary airport extreme router then extend the connection to the airport express to be able to print in N (5.4 Ghrz mode only) especially if your wifi printer works on the G network. 

1-Yes

2-Yes

Use Airport Utility 5.6 to configure the Airport Express G units. And depending on the model of your Airport Extreme, you'll need an additional Airport Utility to manage that unit. These updates happened a few days ago and some people are not happy about the need for two Airport Utilities. You'll need either Airport Utility 6.0 or 7.6.1

while that way is good... i think it is better this person extends their current network to the airport express so to connect it to the printer. It would even be able to be conneted using an eithernet cable instead of a usb printer cable if this person decided to extend the network.

The only airport extreme that is strictly just G (or 54 Mbps) is the (second gen airport extreme router that  looks like the one in this picture of being to the far right.

Sorry, but that is not entirely correct. The 1st AirPort Extreme Base Station (as shown in the picture you indicated) provides support for both 802.11b AND 802.11g Radio Modes. It was NOT strictly just for 802.11g.

This unit was either grey(first gen spaceship) or white (second gen spaceship) and looked like a space ship.

Apple's first AirPort was known as the AirPort Base Station or Graphite. It was so named because it did come with a grayish-colored dome-shaped case. This base station only supported the 802.11b Radio Mode. Soon afterwards, Apple released the Dual Ethernet or Snow AirPort Base Station. It too was 802.11b only, but came in white. This particular base station gets confused a lot with the next series of 802.11b/g AirPort Extreme Base Stations.

Now lets say you have a router but it is using the 2.4 Ghrtz Spectrum that means it is able to use  802.11a, 802.11b, and 802.11g (and maybe also 802.11n) networks.

Sorry, but that is not quite correct either. The 802.11b/g/n Radio Modes support operation in the 2.4 GHz Radio Band; 802.11a/n supports operation in the 5 GHz Radio Band. Note that 802.11n can operate in either band.

The router only becomes an N router if you change the setting to 5.4 GHrtz or if was able to auto adjust.

The non-dual-band or dual-band AirPorts will only become a "pure N" router if you configure their respective Radio Modes to use only one of the "n" only modes. When using any other Radio Mode option, the AirPorts are capable of supporting both "n" and non-"n" wireless clients.

However if you change it to a N only router, that means that you are only using the 5.4Ghrtz spectrum and are not using or sharing the other specturms or radio frequency.

Yes, that would be true for the non-dual-band AirPorts where you would have the Radio Mode set to: 801.11n only (5 GHz). However, you could as easily set it to: 802.11n only (2.4 GHz) and it would also qualify as a "N only router."

While a router is using the 2.4 Ghrtz spectrum, it is sharing or moving between the 802.11a, 802.11b, 802.11g (and maybe the 802.11n) spectrums.

Correct, except for 802.11a which can only operate in the 5 GHz band.

Thank you.

To extend the range of your network, you need to set that up. It's a seperate configuration from printer setup. This article is for Airport Utility 5.1, but I think it's basically the same.

Tesserax can probably help better on this issue, but once you start extending the range your network, that's where you might start noticing slow performance issues.

The first question to be addressed is: In your current network configuration, does the 802.11n AirPort Extreme Base Station (AEBSn) provide adequate wireless network coverage where you need it? If not, then extending this network with your 802.11n AirPort Express Base Station (AXn) would be beneficial. If it does, then leaving all of the Express base stations, configured to join the AEBSn's wireless network would be the better method.

If you actually need or just want to extend the network, please take a look at this Apple Support article to get an idea of what options are available to you ... and if you want to go this path, let us know and we can help you set it up.

So Tesserax - So extending the network with AXn units does not affect the performance of the network.

Was that true with AXg

Can the Airport Express both act to extend the range of the network and also be plugged into the printer to allow wireless printing?

Yes.