An intricate sounding puzzle

All this story started on Wednesday, October 23rd 2019. When I turned on my subwoofer, I found out it was producing a constant noise, even without audio source playing. I verified the connector at both ends, everything was fine. My first reaction was to think the subwoofer was broken. It was too big for me to carry it over some repair shop, and not sure worth doing that, so I was planning to buy a new one. In the mean time, my sound system would still work, although without the subwoofer.

Following is a picture of the back of the subwoofer, with the connector plugged in.

The back of the subwoofer with connector plugged in
The humming sound my subwoofer was constantly making

The best solution to get a new subwoofer, I though, would be to go to the place I purchased my home theater system, but it was in Chambly, near my parents’ place. It would take weeks before I go back there. I thought about waiting but was tempted to check if I could order a new subwoofer online, on Amazon for example, or find a store in Montreal. However, many stores only sell full kits with everything included (A/V receiver, speakers, subwoofer), or all-in-one sound bars.

Finding the culprit: a ball game

After thinking more about it, before buying the new subwoofer, I wanted to make sure mine was really faulty. A year ago, I got issues with my A/V receiver which started to repeatedly power cycle without any possible solution. I replaced it with a new one but kept the old one in case I could find somebody able to fix it. Although flaky, the old receiver could be used to test my subwoofer. If it produces the noise with the old receiver too, I will know for sure it is broken.

To my surprise, the subwoofer worked flawlessly with the old receiver. Of course, it was just a basic test; I didn’t plug any audio source to verify it would produce sound, but the absence of the constant noise was already a progress. Unfortunately, chances were that the problem came from my A/V receiver again, which would force me to disconnect everything it from it, carry it to a repair shop, wait days, and then spend hours reconnecting everything. The speaker cables were quite hard to plug on this one, too close to each other. I didn’t want to redo this and was thinking about giving up and purchasing a dumb stupid sound bar instead. But I was quite reluctant to give up on my speakers.

At least, I was happy I didn’t order a new subwoofer or, even worse, go into the trouble of carrying one into the subway, from a local store back to my place!

Before going into the trouble of disconnecting the speakers, I tried unplugging devices, to no avail. Even unplugging the A/V receiver didn’t stop the subwoofer from making its constant humming sound! Of course, turning off or unplugging the subwoofer stopped the sound!

After more than one hour of plugging and unplugging, trying to replace the subwoofer cable to no avail, having trouble will stuff falling behind my TV, especially the AM/FM antenna of my A/V receiver and a small router configured as a switch to dispatch Ethernet to my HTPC and NAS, I found out that unplugging an HDMI cable from the A/V receiver stopped the humming sound! What? Which cable is that? A couple of crawling later, I found out: the cable linking my A/V receiver to my cable TV terminal. Trying to replace the cable didn’t change anything. I tried disconnecting the cable TV terminal to no avail. I don’t know why I thought about this but found out that disconnecting the coaxial input cable from the terminal stopped the humming. Of course, that would prevent the cable TV from working!

Next step: replace the cable. Unfortunately, I didn’t have a long or short enough cable. The only cable that worked was a 40 feet (too long) one, but the wires going out of the connector were too long, preventing me from tightening the connector into my terminal’s female port. Even worse, when the 40 feet cable touched the terminal’s connector the first time, the subwoofer briefly hummed. I was pretty sure purchasing and plugging a new long enough cable would produce the same effect as the original cable.

I was stuck, because the problem was coming from the combination of my subwoofer, A/V receiver and cable TV terminal. I could by trial and error replace the subwoofer, then the A/V receiver, to no avail! Contacting manufacturer for any of them would just bounce me the others! Only simple “solution” was to sacrifice one of the devices. Short term, it would be the subwoofer. Longer term, I was mentally preparing myself to give up on cable TV. I prefer a sound system over cable TV because I could get contents from elsewhere like Netflix, if of course I can have it played under Linux. I won’t purchase a Windows license for a 10-year old HTPC! Doing this would be a stupid non-sense, for me at least.

What changed?

But that setup was working before! What, on a sudden, changed, and caused it to fail? Well, it was a workaround for a cable signal issue!

I was getting issues with my cable TV terminal since a couple of day, complaining sporadically about low signal and decided it was enough. Wednesday morning, October 23rd 2019, I examined the connectors at both ends of the coaxial cable, they seemed tight, that should work.

The coaxial cable from the wall’s outlet connects into my power bar offering protection for coaxial input. Another cable goes out of the power bar and connects into my cable TV terminal. That worked like this for years, but it seems that every time somebody in my building is getting hooked up or adds a device, the cable signal weakens for everybody else. I thus thought that maybe I could work around by bypassing the power bar, just hooking the cable directly to the terminal. I tested it, that seemed to work, but just turned on the TV, not the subwoofer.

Then I went working and only later I turned on the whole system to watch a video on YouTube. Then I got the issue with the subwoofer and didn’t think at all it could be linked to the cable terminal.

I ended up, Wednesday night October 30th, reconnecting the cable to my power bar. This looks as follows.

Coaxial cable going in and out of the power bar

But then wait a second, wouldn’t that cause the signal issue to come back? Yes, it will. For now, I didn’t observe it again, but I know it can come back. This just gave me a delay, to think about something better, or to prepare myself for sacrificing the cable TV. I need, for that, to test Netflix on my Linux HTPC, which will be a frustrating experience of trial and error.

Why not contact my cable TV provider?

I thought about it and may end up doing it. The problem is that there is little they can do to improve the signal without accessing a technical room in the basement of my building, and getting the key to that room is problematic these days, because the company managing the building is overwhelmed and not responding to every inquiry.

Moreover, my cable company, Videotron, is moving towards Helix, a new technology combining everything into one device. Helix not only replaces the cable TV box but also the Internet modem and would constrain me to use a specific router I know little about. If I’m lucky, the router will just work as a regular device, offering Ethernet ports and 802.11n, hopefully 802.11ac wi-fi, with standard WPA2 and customizable network name and password. If I’m less lucky, network name will be hard coded and I will have to search forever among similar but slightly different names, and I may be limited to 802.11n 2.5GHz wi-fi (no ac, no 5GHz). If I’m really really unlucky, establishing a wi-fi connection will require a proprietary software which may work just on some devices! The problem is if I switch to Helix to get rid of my problems with my current Illico terminal, I won’t be able to know in advanced if all these quirks exist and will be stuck afterwards; it will be hard to go back. Concurrent telecommunication providers are either not offering cable TV at all, either adopting the same all-in-one modem/router strategy.