I think you mean speedtest.net.

Spectrum Modem Update
 

After reading your post, I thought I might as well check out my DL/UL (download/upload) speeds (Spectrum is my internet provider). On my wireless laptop, I did several speed tests and averaged about 110mbps & 11mbps (DL/UL). I checked my Spectrum account and saw that I have the 300mbps & 10mbps service. Since I was getting about 1/3 of the download speed that I'm paying for, I chatted with a Spectrum agent and they asked if they could update my modem software. After the update, my DL speed went from 110 to 307mbps! The UL speed stayed about the same, at 11mbps. I was pretty surprised that the software update to the modem made a huge difference in the DL speed!

Stop wasting your time and get Quantum Fiber if your house has it.

I have Spectrum, 100mbs...

I use a Netgear Nighthawk modem (I forget the model, but it was about $125...)

I routinely get 90-95+ mbs...

Your measured speed is limited by whatever bottlenecks exist between you and Xfinity’s servers. To solve your problem you need to run some tests to find what is limiting your speed. Some possible bottlenecks:
1) problems with the incoming Xfinity cable or signal
2) problems with the xfinity modem/router
3) problems with the connectors or cable between wall and the xfinity modem
4) problems with your router, router cable or router setup (if you have one)
5) problems with the device doing the speed test
6) other problems like speedtest domain’s, VPN’s, dns resolvers etc

I use Speedtest by OOKLA. It works well for me. So, i would suggest checking results from that

If you have spare cables, swap them out first and test again because this is the easiest thing to do.

Next, if you have a laptop ( or desktop), then turnoff the wifi on your laptop and use an ethernet cable to connect your laptop to the xfinity ethernet port. Then run your speedtest.

If your speed is still very low, then the wifi is not the limiting factor… try connecting a different device and run the test again. If the results are still bad then its either the ethrnet cable, the xfinity modem or their incoming signal

if your speed is good on the ethernet connection, then it is something in your wifi setup. You can sort this out by trying speedtest using two different devices (like recent ipads, iphones, samsung phones .. because these have good wifi receivers)

I have xfinity cable (300 mbs speed) and use their grey modem with my 2018 Asus router. I consistently get 250 mbs downloads while using VPN everywhere in my 2000 sq ft home and lanai. Uploads are typically 10 or 11 (which is what Xfinity promises)

But i did have an internet issue for 24 hours about two months ago. I determined that it seemed to be either the xfinity modem or their signal. I took the modem back to xfinity and swapped it. That fixed the problem (Well it was a little more complicated … when i arrived home i found the new modem they gave me had a rattle sound like a loose screw and had to return it for another). No issues since then

1) Do the speed test from the phone's web browser. Is it faster than the PC?

2) Check what the maximum speed is of your network adapter in your PC: Check the Ethernet or WiFi Adapter speed in Windows 10 - Blacktubi it might be less than what you paid Xfinity for.

Use xfinity modem
 

I get 800 using the xfinity modem.

It may not be your Modem… it very well and most likely is your Router. Especially if it is an older one. For the best coverage get a Mesh Router. Check your model and see what it’s limits are. It may have a limit of 100mps.

OP, time to send private messages to the knowledgeable posters here and invite them to a lunch at your expense in return for the following you home to get some specific network design ideas and equipment specs that you get a decent design with which you are happy. . .

Its weird being the same age as old people, but can't think of a better place to be in the same boat together in such a great location as TV

Any idea if age would affect a coax cable?

I have never gotten the same speed on wireless as I have on hard wire. I just went through wi-fi speeds with Xfinity. Hubby's PC is hard wired to their newest router. we found that the speed was under what we were purchasing 850mbps because he uses VPN. Once I rebooted his PC (VPN off), speed was over what we were paying for. All devices on wireless were running at approximately 300-350mbps. We also have an extender. While testing, I unplugged. It did not increase wi-fi speeds. When I take devices near the modem, wi-fi speeds increase (400-450mbps). Metal studs can play havoc with wi-fi which we have and I was told most Villages houses have. It is difficult to find hi speed wi-fi in the North end of The Villages. Quantum was recommended but the reviews were not good. Although Xfinity is expensive and I would like to get our cost down, their wi-fi has been very reliable and their newest router works very well.

Age alone will not affect a cable (the metal doesn't go bad) but age combined with a lot of flexing could cause breaks or tears and age combined with humidity could cause corrosion and bad connections.

One thing that could cause some problems is using an older cable with the new, higher speeds. Coax that worked will for television signals and lower rate signals might not give the best performance with today's higher rate signals. I believe RG-6 cable (should be marked on the insulation) is the proper cable to use. I have a box of older RG-59 which worked well in the past but is not rated for higher speeds.

I had the same problem when I switched to Xfinity. I fixed it by ditching the old cat5e cable from the router to my computer and replace it with a cat6 cable.
Regards,
Pete

Age probably does not impact a coax or ethernet cable unless it is under stress, ie much flexing or the connectors are loose. An old cable can, however impact expectations.

If you have an old e-net cable rated at CAT-5, it is designed to run at 100mbps and 100m max length. It was perfect for its day but if you are trying to exceed those limits you will have issues. Cat-5a increased the limits to 1G bps and 100m. Cat 6 and later 6a increased it again.

The old cable could become a bottleneck depending on how old it is compared to the equipment you are connecting on each end, but a new cable will not make old or slow equipment run faster.

PM me
 

I will save you ma ton of money and give you so much more