Subwoofers

Subwoofer Auto-On / Standby Fixes


Most subwoofers, and many amps, have automatic on or standby settings. The power switch will usually have three settings – On, off, and auto or standby. The on and off are self-explanatory. The auto-on or standby setting is supposed to automatically turn on your subwoofer or amp when it detects a signal. But they don’t always work properly. If you find that your subwoofer isn’t turning on or turns off when it shouldn’t, we have some fixes for your auto-on/standby woes.

It’s that switch in the middle.

How Does Auto-On / Standby Work

The signal coming from your receiver is an electrical one. The electrical signal is detected by the subwoofer and amplified. It is then recreated by the driver in the sub. The auto-on or standby setting waits until it detects that signal before powering on the amp. This saves electricity over time and ensures that your subwoofer is only “on” when it needs to be.

The problem is that this doesn’t always work as it should. There are a lot of reasons why it might not. Faulty output on your receiver, faulty amp, blown fuse…the list goes on. But we are going to assume that the problem isn’t something broken. Instead, we are going to assume that everything is working as it should…but the auto-on / standby still isn’t engaging.

The Problem

In nearly all of the cases that we’ve seen, the problem is a mismatch between what the amp in the subwoofer expects, and what the receiver is providing. If you look at your manuals, you’ll find a voltage range (usually listed as VAC units) that the receiver subwoofer output provides and what the subwoofer amplifier expects. If these are mismatched, the subwoofer won’t engage when it should. This is usually because the voltage from the receiver is too low. The solution that works for most people is very simple.

Solution: Adjusting Trim Level on your Receiver

Go into the audio settings of your receiver. Check to see what level the subwoofer is set at. Is it in the negative numbers? This indicates that the electrical signal will be very weak coming out of your receiver. To fix this, you need to lower the volume of your sub on the subwoofer’s amp.

Hold on. Don’t freak out. We’ll get that volume back.

It’s time to recalibrate your subwoofer. You can do that by re-running your room correction or by using an SPL meter. This will increase the trim level on your receiver higher to compensate for you lowering the volume on the knob. Just make sure you don’t lower the volume on the sub too much. You want the receiver trim to be in the positive numbers, usually around +5dB.

If you see a +10 or +12dB trim, you’ve probably lowered the sub volume too much and the receiver can’t raise the trim any more. Raise the subwoofer volume a little until you get that +5dB on the receiver.

Subwoofer On all the Time

No matter what you do, there will always be a little delay between the time the subwoofer receives a signal and the time the auto-on / standby powers on the sub. If your movie goes quiet for a while (varies depending on sub), the sub may power off again. For some people (I’m in this camp), this is unacceptable. The solution? Flip the subwoofer to the On position and never touch it again.

Check your manual, but for most subs the power consumption is nominal when they aren’t doing anything. The amps are Class D and very efficient. The standby mode might save power, but most of the time it isn’t that much. Plus, you never have to worry about the auto-on feature not working fast enough.

Other Ways to Control Power to your Subwoofer

There is another option, and that is to keep the subwoofer power switch set to “On” but controlling whether the sub is getting power from the outlet. Some home theater power strips can do this, as can remote control outlet adapters. We don’t normally recommend this solution as subwoofers are energy hogs. When they are in use at least.

To create those couch-shaking bass notes, they need gobs of power. Not for a long time, but a lot of power very quickly. Many home theater power solutions limit the available power. While you’ll get 15 amps from the wall, the outlet adapter or surge protector may limit their outlets to 10 amps or less.

If you decide to get one of these solutions, make sure that they will pass through the full 15 amps (don’t be fooled by “compatible with 15 amp” claims – that doesn’t mean they will pass all that power through). APC is a company that is up front about exactly what their power solutions can do and you can trust if they say an outlet passes 15 amps, it does.

Conclusion

Using the standby / auto-on function of your amp or subwoofer should be easy. It should just work. Most of the time it does. But if you run into problems, one of our solutions will help. Do you use standby or auto-on with your amp or subwoofer? Have any issues? Let us know in the comments below!


14 Comments on Subwoofer Auto-On / Standby Fixes

  1. You know people who make these subs could easily solve this issue. There is nothing worst than listening to a dynamic movie and the sub constantly clicking off and then on again and the bass rushing in (due to the delay). All the manufacturers have to do is put a time delay. So if no signal is heard for 1 hr, then go to standby. This would make sure that during average listening the sub is on. And when you go away, like to work. The sub is off, when you do not need it. So simple. Like every other electrical device (tvs etc).

    • In every subwoofer we’ve ever tested, there is a delay. Not usually as long as an hour, but there is one. But even with an hour delay, this could be an issue. Think of the movie The Professional. There is almost no bass in that movie until the explosion at the end. It wouldn’t be inconceivable for a subwoofer to switch into standby mode for most of that movie until that explosion.

  2. Connie Carter

    I am seeking a device, like the standby mode of a sub, which will turn on the power to amplifiers when an audio signal is present and off when not. It would be a small black box with ac in and ac out that is controlled by the presence or absence of an audio signal.

    • Most if not all standalone amps have this. It is called a 12-volt trigger. Your processor or receiver and amp will both have a 3.5 port. The amp usually comes with a cable but you can find one for cheap easily. When you power on the receiver or processor, it will send a signal to the amplifier through the cable to “wake it up.”

    • You can add a smart plug (like this) and use that. Just make sure that it is rated for the full power your subwoofer’s amplifier will be pulling from the wall. If you are looking for something that will replace the auto-on feature (detect when a signal is or isn’t coming from your receiver and enable/disable the power), none exist that I know of.

  3. Alan Whyborn

    I came across this discussion while looking for solution to an issue with my system. My new amp DOES have a trigger output, but my old sub has neither an auto standby OR a trigger input (my old amp had a switched mains output on it – the sub was plugged to that so it was only powered when the amp was on). Is there a triggered mains power adapter available in Australia? (I’d prefer to NOT use a master slave power board because I don’t want my sub on when I am listening to music in zone 2 – verandah).

    • APC units made specifically for home theater (now all discontinued) used to have outlets that you could control with a 12v trigger IIRC. Sadly, their newer Back-UPS units don’t. On Amazon here in the States, I can find a couple of products by searching for “12v trigger outlet” (example) but they are quite expensive and most are discontinued. Sadly, I couldn’t find anything similar on Amazon Australia. The one thing I’d watch out for is that whatever solution you get it allows through the full power from the mains. If it doesn’t, it can blow the fuse in the subwoofer amp. Sorry I couldn’t be more help.

  4. Shawn C

    I am having an issue with my auto/on switch. Even though it’s set to auto, even when my receiver is off, the blue light stays on constantly. I have a Klipsch Sub-10 which is not produced anymore. It works perfectly other than this issue.

    • I’m assuming it switched to red when in standby mode. I’m also assuming that you have checked after a considerable time. Many auto-off functions take at least 15 minutes to kick in.

      If the sub is very old, it could be a number of things. That auto-off could be malfunctioning. My guess would be that a newer receiver may have more output voltage coming from the subwoofer output than the sub is expecting. This could trick it into thinking it should stay on all the time. You could adjust the volume on your subwoofer up and the trim level down to compensate. No guarantee it would work but it might.

      Generally, I wouldn’t worry about it. The draw from a subwoofer amplifier that isn’t actively in use is low (I’m sure you can look it up somewhere). I keep mine on all the time so I never have to worry that the auto-on failing.

  5. Richard

    I also have issues when listening at low levels like in the evening. My KEF Q400B keeps shutting off.
    I don’t understand that this issue is not dealt with by the manufacturers. One extra wire from the av receiver to the sub could hold a on/off signal. This could imply one extra wire or another design to connect the sub like a cinch connector as found on a headphone.

    • Some subwoofers have 12volt triggers. This is a simple cable that turns on the subwoofer when your receiver is powered on. Not as common as the auto-on functions, but some subs have them. Not yours, however.

  6. Gary L

    I was thinking of getting a smart green power strip like this https://amzn.to/3PB8dIA and plugging in my receiver into the main outlet and my subwoofer into one of the triggered outlets (it detects when one device is on, and is adjustable). It’s a LOT bigger than I need as I keep my TV and get plugged into a UPS. The real question is: how much does my subwoofer use when I’m not using it…

    WHAT I WANT is an outlet that’s just triggered by a USB port as my receiver has a USB port, if there is power on the USB, then turn on the outlet. I can’t believe this product doesn’t exist…

    • Your user manual should tell you how much power your sub uses in standby or idle. Or reach out to your manufacturer. The amps used in subwoofers are quite efficient so it likely isn’t much.

      I could see no information on that product if it limits the current. I imagine it does but it isn’t listed. If it limits the current at all, it could damage itself or your sub (or both). The problem is that if it limits the current (to 10 amps usually), and the subwoofer is looking for 15 amps, then then get in a bit of a war. The subwoofer keeps trying to pull more power and the protector keeps trying to shut it down until one of them breaks. I’ve had it happen to me before.

      Most importantly, nearly every comment complains about the “child” outlets having unpredictable behavior if power fluctuates. As a subwoofer amp will gobble large amounts of power briefly, and then nothing for long stretches, I doubt these two products would get along.

      Lastly, and most importantly, every subwoofer manufacturer I’ve ever spoken to has warned against using surge protectors with their products. They usually have a fuse for just that purpose.

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