Download Speed Varies Between Computers

[Jernah]

Hello everyone, so my download speed is acting very weird. I'd been noticing some lag while gaming on my desktop, however my ping was perfectly fine when ever I'd have these lag spikes so I did some speed tests. My desktop gets around 10mbps down and 10mbps up, while my laptop gets 50mbps down and 10mbps up. I thought this was really weird and did the test many times with the same results, so I moved on to using other computers in the house with more odd results. Generally the upload for every computer was 10mbps but the download would vary from 25mbps and 40mbps (not including the desktop and laptop previously mentioned). I've run multiple virus scans on my desktop to see if that was the issue with no positive results. I'm really not sure what the cause for this is or any ways to fix it so any suggestions are appreciated!
Thanks!

 

[Someone Somewhere]

Are you using WiFi? WiFi is very sensitive to things like antenna placement and interference.

 

[Jernah]

Are you using WiFi? WiFi is very sensitive to things like antenna placement and interference.

All the computers I did the speed tests with are using wifi, I've tried adjusting the antenna, placements of the computers, antenna on the router all with generally the same results.

 

[Someone Somewhere]

Do you have a spare ethernet cable you can test with?

Are all the WiFi cards and router 802.11n or 11ac, preferably 300Mb/s+?

Unfortunately, there's not going to be a huge amount that can be done, I suspect.

 

[Jernah]

Do you have a spare ethernet cable you can test with?

Are all the WiFi cards and router 802.11n or 11ac, preferably 300Mb/s+?

Unfortunately, there's not going to be a huge amount that can be done, I suspect.

This is the wifi card for my desktop: http://www.newegg.com/Product/Product.aspx?Item=N82E16833166073
I have no idea about my laptop (which is a mac) or most of the other computers I tested with.

Also I unfortunately do not have an ethernet cable to test with, couldn't really plug it in anywhere either as the router is two rooms away.

 

[USAFRet]

As said above, WiFi performance is very sensitive to placement, etc. In my house, I can see a 20% difference just walking 15 feet down the hall upstairs.

 

[Jernah]

As said above, WiFi performance is very sensitive to placement, etc. In my house, I can see a 20% difference just walking 15 feet down the hall upstairs.

I thought that might have been the problem too, so when I was testing the speeds of other computers in the house I brought my laptop that got 50 down 10 up along with me and after testing one computer I'd test the laptop in the same room and get the same 50 down and 10 up.

 

[Jernah]

This is also my router if this helps at all: http://www.buffalotech.com/products/wireless/open-source-dd-wrt/airstation-highpower-n450-gigabit-dd-wrt-wireless-router