At you surmised, the wireless speed of the local network has nothing to do with what your ISP is providing you and, is almost all cases, is much faster.
Where the wireless speed on the local network comes into play is for data traffic moving between devices on the local network. For example, you would notice a significant difference using wire vs. wireless connections when streaming HD video from a NAS device to the media player ... but little or no difference between streaming the same HD video from the Internet.
The 5 GHz band currently offers two advantages over the 2.4 GHz band: 1) More bandwidth due to a combination of wider broadcast channels and signal physical characteristics, and 2) Less prone to interference ... until this band catches up in popularity.
The disadvantages of the 5 GHz band are shorter range due to signal attenuation free space loses and less ability to penetrate through objects like walls. In practice, the 5 GHz band is only useful in the same room as the wireless access point.
This means, although a speedtest would show the same value for both bands, 5 GHz has more bandwidth and handles tasks like streaming HD videos better
Yes, that is correct! Another way is to measure throughput (data rate). Think of bandwidth as the number of lanes available on a highway, throughput would be the direct result of the number of cars/trucks using those lanes. As you can imagine, traffic will back up in two basic scenarios: 1) With the same number of vehicles, have fewer lanes, and 2) With the same number of lanes, add more vehicles.
The first is an example of the overall bandwidth rating of a wireless network. The very latest 802.11n networks running on the 5 GHz band can have a bandwidth of over 450+ Mbps. That's a lot of lanes! Compared to the prior generation 802.11g networks that had a maximum of 54 Mbps.
The second is an example on how much traffic the network can handle or throughput. So having more lanes improves throughput. When simultaneously streaming HD video, performing over-the-network backups and moving files between computers over the local network, you will want as much bandwidth as possible to handle all of that traffic.
Speedtest does NOT measure local network throughput. Instead, it like a number of other utilities like it, will attempt to measure the overall throughput between your computer and the Speedtest server.
If you want to get an idea of the throughput of your local network, I would recommend a free utility provided by AJA Video Systems, called AJA System Test. You can then establish the current baseline, and then, as you make changes to your network, see the results.
Thanks a lot, I'm learning some new things.
Different question: My Airport Base Station is set to 802.11n (5 GHz) 802.11b/g/n (2,4 GHz). Looking at the wireless clients tab, all my 2,4 GHz clients are connected with a b/g connection, although they are all n capable and there is no b/g device in the network. Is this normal?
I'm not 100% convinced that the AirPort Utility's Wireless Clients tab is always accurate. Another way to verify the Rate that you are connecing your Mac at is by holding down the Option BEFORE clicking on the AirPort icon in the OS X menu bar.
For the 2.4 GHz clients, note both the PHY Mode & Transmit Rate readings.
Another thing to try is to remove all 2.4 GHz clients, and then, add them back by connecting them one at a time. Do each show up as 802.11n or 802.11g. How about their Transmit Rate values? Do they show up at 54 or at a higher level?