Home Theater Geeks 447 Transcript

Please be advised this transcript is AI-generated and may not be word for word. Time codes refer to the approximate times in the ad-supported version of the show.

00:00 - Scott Wilkinson (Host)
In this episode of Home Theater Geeks I answer a question from a listener who has an irksome problem. When he turns off his AV receiver, the subwoofer pops. I do have an answer, so stick around.

00:16 - Russ (Caller)
Podcasts you love.

00:17 - Scott Wilkinson (Host)
From people you trust. This is Twit. Hey there, scott Wilkinson, here the home theater geek. In this episode I answer a question from Russ Wiley from Paso Robles, california, who sent in this voicemail.

00:45 - Russ (Caller)
My name's Russ. I'm calling from Paso Robles, california, who sent in this voicemail? My name's Russ. I'm calling from Paso Robles, california. I bought a Yamaha home theater receiver about 10 years ago and I have it connected to a Velodyne subwoofer and for these past 10 years when I've used it and I turn off the system, a popping noise comes out of the subwoofer. And now sometimes it's just a mild little thunk, but sometimes it's a pretty loud popping noise that it's a little disconcerting and I was just wondering if that's normal. I mean, is it normal for that? And should I have? I mean, I have not been kneeling and turning off the rocker switch on the back of the subwoofer for the last 10 years. I've just been turning it off and on anyway. But I'm about to buy some new replacement equipment, get a new home theater system and some new speakers, and I just want to know what the expectations are so that when I buy the new equipment, whether I should expect this behavior or not. So that's my question. Thanks a lot. Enjoy the show. Bye.

01:47 - Scott Wilkinson (Host)
Thanks, russ. Yeah, that's a good question and it happens all the time. It's a very common occurrence. First things first, it's not harmful to your subwoofer, so please don't worry about that. It is annoying, however, so let's see if we can solve that problem for you.

02:06
I can think of three things that might cause it. One is a transient signal from the AVR. When you turn it off, it sends out a little short transient signal. It might be something called a DC bias voltage on the AVR's output. So some amplifiers amplify the signal, which is an audio signal. It wiggles up and down, and the voltage around which it wiggles might not be quite zero. And so if it's not, then as you turn the amplifier off the AV receiver in this case the voltage suddenly does drop to zero and that causes a little transient. The third reason could be a mismatch in ground voltage levels between the AVR and the subwoofer.

03:11
Now I've looked at both of those units the Yamaha AV receiver RX V577, as you wrote in a letter, e577, as you wrote in a letter, and in this picture you can't see the plug, the power plug, but in other pictures I have seen it's a two-prong power plug. In other words, it's not grounded, and the same is true of the Velodyne CT80, which I found a picture of. Here's a picture of it from the front. It's a front-ported subwoo of. Here's a picture of it from the front. It's a front ported subwoofer. Here's a picture of it from the back. And if you look carefully at the plug which is kind of wrapped up in the power cord, it is also ungrounded. It's just a two-prong plug, so they could very well have different ground voltages within their respective circuits and in that case then when the AV receiver gets turned off, that discrepancy becomes evident in a thump or a pop.

04:21
Now, as you probably know, the best solution is to turn off the subwoofer before you turn off the amp or the receiver. But, as you also point out, reaching down to turn off the subs rocker switch, which is at the bottom of the back panel, is kind of a pain. You don't really like to do that. I wouldn't want to do that either. So I have a recommendation, and that is what's called a remote controlled AC outlet, such as this one on Amazon. It's from a company called, I think, dewinwills, chinese company. There are millions of them D-E-W-E-N-W-I-L-S, dewinwills. It's an indoor remote control outlet. So what you do is you plug this thing into an outlet and then you plug your subwoofer into it. It also comes with a little RF remote control, so it doesn't need to be line of sight it could be hidden behind equipment and it has two buttons on and off. You can also turn it on and off from the unit itself in case you lose the remote, which is, I think, very good, but that would let you turn off the subwoofer before you turn off the amp, and that would mean that you wouldn't hear that popping noise.

05:51
Now, I had never heard of this company, dewinwheels before, but according to the specs, it can carry up to 15 amps or 1,875 watts, which is plenty for your subwoofer, which I believe has an 80 or 100 watt amp in it, and it's less than 12 bucks on Amazon. In fact, I use that very one to turn on and off my entire amp rack in my home theater. Primarily, I do that because the amps can certainly be kept on all the time, but they're in a relatively closed rack and so, and even though they are separated by a little bit, I have not put them smack up next to each other. I'm still a little concerned about heat, so I turn them on once in the morning and I turn them off at night, and when I do that I do in fact get a very low level little pop out of the speakers which is very low level. I'm not at all worried about it you shouldn't be worried about the one you're hearing either but if you want to deal with it, then getting one of these remote controlled AC outlets would be a good answer.

07:14
Now you're about to get some new equipment, so I would definitely, I would hope that the equipment you get would have grounded plugs and that you would plug them into the same circuit, the same AC circuit, so one outlet from the wall maybe to a power strip. Plug them both into that power strip as an experiment. I don't know whether your two pieces of gear as they are now are connected to the same circuit or not. If they're not, I would perform the following experiment I would plug them both into the same outlet with a power strip or a splitter of some sort and then see if the problem happens. If it does, then that lends credence to my idea that it's probably a mismatch in ground levels, although it may not make any difference because those plugs are ungrounded. So it's just an experiment to try, but you're about to replace the equipment anyway, If you can get equipment with grounded plugs and plug them into the same circuit.

08:22
So I hope that has been helpful. Now, if you have a question for me, you can send it along to htg at twittv and I'll answer as many as I can right here on this show. And, as always, we thank you for your support of the Twit Network with your membership in Club Twit, which gives you access to all the shows we make in video form, and you can come into the Discord channel and hang out with like-minded Twits. So we hope to see you there. Until next time, geek out.