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!


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