Talk about modems

May be a dumb question- I have an existing Xfinity cable line that comes into my home office, where I have an Xfinity [xFi Gateway] modem/router for my office computers and wired xfinity telephone. That Gateway produces wifi - and I use xfinity’s flex box (free) for my TV watching.

I wanted to go hard-wired for my audio system rather than going wifi/mesh system into my living room where my audio system is (and I’m renting so I can’t string a 50’ ethernet through the wall, into the attic, back down the other wall, etc), so this month I have started an additional Xfinity line/service into my house-just $25/mo.. Haven’t gotten it installed yet, but I got an Arris SB8200 modem (for the existing coax jack that comes into my entertainment system area in the living room-separate internet-only line). The coax [cable] comes into the modem, and an ethernet cable is going to my streamer, (and USB or AES into the DAC).

Why would I need a router or switch(es) between my modem and server/player, if I’m just using that cable line for audio/entertainment closed system only? (no house wifi/networking)

I realize that there is likely just one line coming into the house Xfinity/Comcast, so I'm not clear on how I will be receiving two 'services' - one into my home office and one into my living room. But I assume Comcast can activate another service on the same physical line.

You can connect modem directly to streamer, hopefully that modem is Broadcom chip based. The only issue I see is how does your remote or control device see streamer on another network, my smartphone or tablet require wifi. Seems to me you're going to have to control streamer at the streamer itself, unless you can configure a remote device to see the other network where streamer resides.

If you're having second line installed by Xfinity/Comcast, should be seamless install. If doing self install, I'd assume you'd need switch somewhere in IPS line to segregate the two services. My ISP line has switch to segregate tv service from internet.

Thanks very much sns.

Yes, the Arris SB8200 has the Broadcom chip; recommended by xymox over on whatsbestforum. It has a wall wart power supply, so I am looking at a potential LPS for the modem (and maybe the fiber media converters - see below).

xFinity/Comcast has sent me a ’welcome to your new service’ email last week, saying ’let us know when you are ready to activate it..’ I assume I will have another home wifi network, though here is what I found on that question:

Q. Does Arris SURFboard SB8200 have Wi-Fi?

A. Connecting a Wi-Fi router to the SB8200 is recommended when there are multiple client devices in the home network. NOTE 2: It is possible to connect when there are multiple client devices in the home network two devices to the SB8200. However, the cable provider must provide Internet IP Address to each device for Internet access.

So it sounds like I will have 2 wifi networks coming in [on the same cable coax], and would just use the one in the living room for audio (and wifi from the SB8200 modem to a tablet to control the [hard-wired] streamer). Another possibility is to run an ethernet cable from the back of my modem (or streamer?) to a tablet or laptop in my listening seat. My existing XFi modem/router would still stream wifi to the TV’s flex boxes in the living room and bedrooms.

I realize that another thing I may run into is noise - coming in/through on the cable coax line, so I may end up needing to do the "ethernet to fiber back to ethernet converter(s)" process. Though I don’t think I will need another router, switch, or ether regen, etc. since the entertainment system will essentially be a ’closed’ system. Not totally clear(?)

Will keep this modem thread posted on learnings.

Thanks again.

Why would I need a router or switch(es) between my modem and server/player, if I’m just using that cable line for audio/entertainment closed system only? (no house wifi/networking)

@westborn 

As mentioned, having 2 networks will make access tricky.  You want a router between you and the modem because of the firewall features. A simple modem won't have this important internet safety feature, but the more integrated modem/routers will.  The latter usually have 4-5 Ethernet outlets.

@westborn Just looked at your new modem. The SB8200 has two ethernet ports, one will go to streamer, other to remote control device. Most likely you're going to have to use a laptop as this device, and it must have ethernet port, everything hard wired, don't need wifi at all. The laptop will be provided permanent IP adress. Very unlikely your tablet has ethernet port, extremely limited number do. Not all laptops have this provision as well, in which case use usb to ethernet port conversion device. You don't have to worry about wifi with this setup.

Telephony or having telephone connected to modems is another concern because of contamination/ noise. Don't connect phone to modem, most ISP have dedicated phone modems, just have to ask.

I purchased an enterprise level managed router couple months ago, has NO wifi capability. My intention is to experiment with completely isolating audio system from wifi contamination. I have Trifield meter which measures emi in form of rfi, wifi capable routers are one of the richest rfi environments, read noisy components connecting to our audio systems. With the managed router, wifi can be segregated to separate branch.

Keep us informed, will be interested to hear your outcome in regard to sound qualily.