How many AP Extreme's?

Too many variables to say - depends on layout, construction, RF sources, etc. etc. But if you put your house into the middle of a bell curve of typical construction and other conditions, I'd say the three units you have is plenty.

 

I have two story house same dimensions (roughly 2100 sq ft) as well (concrete + mortar) and I use two and get Wi-Fi around the house (except kitchen area) and even in the lawn.

 

I have 2,000' on a single level plus basement. The AirPort Extreme is just about dead center in the house. Reception is excellent throughout the house and basement. It gets a little weak on the outside of the garage but that puts a lot of metal in the way.

I usually only use wireless for idevices and hardwire any computer or device that's in a fixed location.

 

I have a 2600 sq ft single level and I used to use 3 AEBS in a triangular layout to get the best WiFi spread, all were wired CAT6, with a gigabit switch in the attic... anyways, now I have updated to just 2 AEBS 802.11AC routers and my coverage is just fine.
I have 1 router at the front right of the home and 1 near the rear right side and I get at least a 500+ Transmit Rate (option clicking the WiFi in menu bar) at even the furthest points.

I also hardly run anything on WiFi that doesn't have to be. Wired is much quicker and makes bridging router much more effective.

 

With 2 aire ac, do they communicate between them faster or same comparing to 1 aire ac with 1 aire no ac or express?

 

I think what you are asking is if you use one Airport Extreme as a wifi extender, will two Airport Extremes with AC communicate between each other faster than One Airport Extreme with AC and One Airport Extreme/Express with N correct?

The answer is yes two with AC will communicate faster since they can use the AC as their "link"....

However, what you SHOULD be doing is using ethernet and setting the second Extreme in Bridge Mode. Why? Because you in essence cut your wifi bandwidth in half due to the "extended" Airport extreme having to send and receive to the main Extreme with each wifi call. If you use ethernet and bridge mode then the link between "stations" is the same (all would be using gigabit speeds regardless if using AC or N only stations).

Also another loss you have with mixing both an AC and Non-AC extreme is that you will only have limited AC coverage. Not exactly ideal.

I have a 2 story home with finished basement and have the house covered in a vertical triangler pattern:
1. Office in basement at one side of the house
2. In Rec room in basement on the other side of the house
3. In Guest room on 2nd floor in the middle of the upstairs

These are all 2011 Airport Extremes.

My plan is to move to 2 AC units eventually, but I haven't figured out the "best" locations for them. I might leave the main Extreme N where it is in the office and turn off the wifi. Put one AC unit in the middle of the basement and replace the one in the guest room upstairs. The AC units supposedly do a better job of wifi coverage. Worst case is I add a third one on the main floor in the kitchen (not ideal per the wife!).

 

Thanks for your reply. I just want to confirm something:
So currently, I have 5th gen AE and 2nd gen AX. If I want to take advantage of AC, I should buy 2 new 6th gen AE and set both of them in bridge mode (when in bridge mode, it provide extended wifi coverage)? In addition, I can use my 5th gen AE or AX to use as wifi extended only to provide further coverage that I don't need speed too fast?