OK, that will really help, as mobile devices like iPhone, iPad, etc are not very good wireless performers at all.
For the first "test" please locate your laptop about 8-10 feet away from the AirPort Extreme with clear line-of-sight between the Mac and AirPort.
Run a speed check and note your results. How does that compare to the direct wired Ethernet connection when you connected directly to the AirPort Extreme?
Next, move the laptop further away.....20-25 feet or so, but still with clear line-of-sight between the Mac and AirPort and note the results.
Next, move the laptop into the next room, so that there is one wall in the signal path between the Mac and AirPort and note your results.
Next, move the laptop such that there are 2 walls in the signal path and note the results.
Finally, move the laptop as far away as you would ever normally need in the house and note the results that way.
Post back when you can with your findings.