Terrible wireless speeds with AEBS 4th Generation

I have no problem with the internet throughput from my Airport Extreme Base Station 802.11n (4th generation, v. 7.5.2) to my iMac.

BUT...the speed slows down dramatically (from 16 Mbps measured by Speedtest on the iMac) to approx 2 Mbps on my iPhone 4 or iPad 2, even when they are in the same room as the router!

I've tried using iStumbler to see if any nearby routers are using the same channel (I changed from 11 to 9), tried using the Guest Network setting, but nothing has worked.

Any other suggestions?

Thanks!

That is a strange one. Let me try the same speed test on my iPhone/iPad here as on my iMac and I will report back.

I have the same AEBS with 7.5.2 and my line is 12Mbps which I only get 11.41/1.41
on Uverse wired or wireless but both my iPhone and iPad get 10.80/1.41.
With that said I would definitely check your AEBS settings keeping in mind that the iPhone will only do N on the 2.4GHz radio not 5 GHz and my iPad although N capable likes 2.4GHz better.

I am using a Dlink DIR-655 and DSL. My speeds on the iPad were the same as on my iMac but my DSL is 3MB. Maybe at faster speeds there would be more difference. Yours sounds way too high to me though.

Are you using the exact same speed test on all systems?

I used Speedtest.net for all 3.

Same here as there is an app for IOS for SpeedTest.net so figured it would be the best one to compare.

I had a similar problem with a Time Capsule and some Airport Expresses - with my iPhone and iPad. I would get less than 1Mbit on wireless even though wired was over 20Mbit. I upgraded my Cable modem to a DOCIS 3.0 capable modem and I now get a similar speed ~20Mbit wired or wireless. It also shows when using streaming video like Youtube - the performance is much better on my iOS devices. The only thing I changed was my cable modem.

All tests performed using Speedtest.net