New AirPort Extreme and 802.11ac configuration

Start with normal defaults.

ie band swapping is left to the Mac and SSID is identical on the two bands.

If you then find the Mac is making poor choices.. a distinct possibility. And it is important to you..then set the SSID on 5ghz to a different name.

Speed on 2.4ghz should reach 217Mbps and that probably exceeds your internet speed by a far margin.. (you need at least x2 the internet speed for wireless to keep up, ie if internet is 100mbps then wireless should be 200mbps at least due to half duplex nature of wireless). If you have multiple items some should be forced to 5ghz that can manage it..

what is the meaning of "automatic", "numbers" and "off" in the wireless setting menu ? when i "off" 2.4ghz, some of my Android Device won't recognize wifi,(I still have the 5GHz) then I pick "10", it works again.

Apple devices has no such problem.

2.4ghz and 5ghz are controlled by the same setting..

If you select Off then both bands are off.. there is no way in apple routers to turn off one band and keep the other working.

In the wireless options tab.. you can select automatic or a wireless channel.

Here is my current setup.. both bands have the same name..

2.4ghz has a fixed channel.. 8.

5ghz is automatic so it will pick the best channel at turn on which has the least interference.

It can also use channels unavailable in manual selection.

So if I check the channels in 2.4ghz it will be 0-11 or 0-13 depending on your location.. they are pretty uniform around the world.

But 5ghz has a lot of variation.

If you check the computer option click on the wireless fan .. you will see what is actually happening.

You can also open the wireless diagnostics and do a scan of the current wireless in your area to make sure it is optimised as well as possible.

TThank you very much for your helpful answer. One more question

Does 5ghz recognize by all devices like 2.4ghz OR there is some difference ?

5Ghz is pretty much standard in any thing you bought in the last few years..

Earlier products are 2.4ghz only. The early model airports N wireless airports, say Gen1 and 2 Extreme, Gen 1 Express and Gen1 TC were all single band devices.. but could be set to either 2.4ghz or 5ghz.. although most people would be forced to use 2.4ghz for compatibility. Since then all airports, (Extreme, Express and TC) are dual band simultaneous. You have both bands or nothing.

Say you still use iphone 3 or 4 .. it cannot use 5ghz.. An iphone 5 added 5ghz..

So it will depend.. newer stuff.. certainly for apple will use 5ghz.

Other brands depends.. a cheap PC laptop for instance may cut corners and use 2.4ghz only. Game console etc might still be single band..

So it will depend.

many thanks. It really help.