Can you tell me what Modem you are using?
It should be located on Bottom or side of the unit.
Is it a Comcast/Xfinity Modem?
and finally is it a wireless gateway or just a cable modem?
The Xfinity techs ( Sorry to some that are decent) Mostly are pathetic and I have no Idea where they acquire them, I have been in many heated Battles with them on many occasions using this exact site and the awesome ability to archive past tests, had them say testmy.net is not a reliable tests and they shoot off to some Xfinity sponsored test site and say see you getting Such and such speed all is good, then I pull up the archive and say Ok explain why a week ago I was getting this speed down and up and then ( Look here pay attention) at this date the speed goes down the well lets says it just plummets.
SO No matter what you think of your test links I have proof I was getting this speed and now I am not.
I actually told one tech he could not come into my house just give me the modem and be on your way because he started off blaming everything he could name as to why my speed was slow, I am surprised he didn't blame my cat for his color of fur as to why my internet was slow.
But just as I had figured It was the modem that was going south and once I exchanged it I was back up to speed.
Of course that a while ago and speed was I think 20Mbps down where now I am getting I think roughly 65Mbps, but they advertise my package is supposed to be running at 105Mbps down and 25Mbps up but Surprise Surprise they advertise things before they can actually provide it, but that is a whole different can of worms.
Sorry for wandering off you issue.
So if you could get some info It may help me possibly help you some I sure hope anyway .
Have you checked your TCP/IP settings? There is a site that has a great analyzer if I am allowed to mention it, I only ask as Somehow my setting got all messed up my MTU was something insane like 2800 they also have a neat tool called TCP/IP Optimizer that could help you get the most out of your connection.
your statement where you had gotten better speeds on other devices almost sounds like something in you computer is set incorrect, but even that being said you are not getting closet to the correct speed with those other devices either I would expect 40-45 Mbps if you have the 50 package, BTW you do have what they call Blast and not performance correct?
spudler_t's post in Speeds are over 99% slower than what I should have with Xfinity (Comcast) was marked as the answer