Introduction: Disable the Sleep Feature in the Presonus Temblor T8 Subwoofer
It took about one day for me to realize that while the Temblor T8 is a great sounding subwoofer, I hate its auto-sleep feature. It takes too long to wake up, it shuts down when you’re listening at quiet levels, and it pops like crazy every time it comes back. After checking other Amazon reviews, it was clear that I wasn’t the only one with that complaint. So I decided to fix the issue and document it for others who might be interested.
With this project, your speakers will always be on. This doesn't fix the pop, but it does mean that it will only happen when you choose to turn the subwoofer on and off.
Step 1: Disclaimer: Don't Be Dumb
This project involves working on electronics that operate at mains voltage. As such, it is DANGEROUS. Do not attempt this project if you aren’t comfortable with that. This is also an unlicensed modification: it will definitely void your warranty, and if you do it very wrong you could destroy your equipment. I’m not responsible for anyone who blows up their subwoofer, burns down their house, goes into cardiac arrest, or is otherwise mutilated during the course of this modification. That being said, it’s really pretty easy.
Step 2: Tools You Will Need
Soldering iron (plus very basic soldering skills)
1 piece of wire (about ½” long)
Step 3: Get Started
Turn off the subwoofer, unplug the power, inputs and outputs, and take note of all of your settings (they are easy to bump while you’re working on the circuit board.) Next, remove the 10 screws that hold the subwoofer panel onto the sub box (circled on the picture) and carefully pull out the panel. There’s really nothing to grab onto to do this, so I ended up tipping the subwoofer until the panel started to slide out.
Be aware that there are two pairs of wires that are attached from the panel to both the speaker and the LED logo on the front of the box. There should be enough length in those wires that you don’t have to disconnect them at either end, but be careful not to stress them or they could break at the solder joints. I found that the easiest way to work on the circuit board was to flip the panel upside down and place it back into the opening that it came from.
Step 4: Solder
You can now see all of the electronics that power the subwoofer. The part that we need to get to is on the underside of the top blue circuit board. I removed the black steel cover plate by unscrewing the three screws that hold it to the heat sink (circled). You may find you don’t need to remove it, but I think it makes the process a little easier. Once removed, take a look at the exposed circuit board. If you are smart, you will drain the large capacitors seen on the left side. Google “discharging capacitors” for a better explanation of how to do that than I can give you.
Done? Alright. The part we need to bypass in order to deactivate the sleep mode is a black rectangular relay on the right side of the top circuit board (see picture 2.) It is marked HF32FA. Basically, this relay acts as an automated switch. When it senses enough volume, it connects your speakers to your inputs and allows sound through. When it doesn’t see that volume, it disconnects the speakers and everything goes to sleep. We’re going to ignore the complicated sensing circuitry and simply force the speakers to stay connected.
To do this, we will wire two pins on the relay (the switching pins) together permanently. These pins are located directly underneath the relay. It’s a little difficult to locate the exact pins, so be sure to take care finding the right ones by looking to make sure they are directly beneath the relay, and referencing the location of the text nearby. If you connect the wrong pins, I cannot vouch for what will happen. But it will be bad.
It’s not critical what you use to connect these pins, but it should be a decent sized wire. If it’s too thin, it will be fragile and may not pass enough current. If it's too large, it will be tough to work with. I cut the leg off of a large resistor and used that. You could also use stranded wire, but it would be a little harder to install. Use common sense here.
Solder that wire jumper between the two points. I did this by soldering upside down. You may find it easier to unscrew the circuit board so that you can work right-side up. I didn’t do that, so I won’t tell you how to do it. If you do it my way and solder upside down, be sure to place something on top of the lower circuit board so that if solder drips, it won’t connect things that shouldn’t be connected. I put down a piece of paper, but something that won’t burst into flames might be even better. Once soldered, snip off any extra length on the jumper. You want to be 100% sure that your wire is not touching anything other than those two points. There are high voltages in this area of the circuit board during normal operation, and if you short circuit 120 volts through your speakers, they will blow up and you will get mad at me. And I will point to this section where I said “be 100% sure that your wire is not touching anything other than those two points.”
Step 5: You're Done
Now that the two points are soldered together, you’re done! Re-assemble everything, re-connect, check your settings, and test to make sure that it works.
If you ever decide you want the sleep feature back, just open it up and remove that jumper. If you really wanted to get fancy, you could use a toggle switch instead of a jumper wire so that you could turn the sleep feature on or off.
Note: I realize this isn’t a perfect solution. It would be better to adjust the volume threshold so that the sleep feature doesn’t activate with quiet material, and to add more filtering to remove that pop. If anyone takes the time to do that, let me know! Until then, this is a quick, easy fix—especially for people who power down their systems when they’re not in use anyways.