Control Resonant’s The Complete Set quest sends you on a tour of the city to find a few speakers and a subwoofer, after which you’ll need to bring them to the Auction House. You will have to locate all of them, place them in their rightful places, and switch them off as soon as they begin functioning. Here is a step-by-step guide for this quest.
How to Start The Complete Set Quest

Bug Notice: The quest is currently bugged, and some tips that could help when you encounter the glitch is to leave the area and come back, or defeat all the enemies on the rooftop and use the door to get inside the building. Another tip that could help is to keep talking to the woman NPC while staying close to her and continue to speak to her until she stops saying no. Then, wait for a few seconds before interacting with the Subwoofer.

The Complete Set begins in the Downtown Auction House. Go to the Auction House and get inside. In the Auction House, you will find a speaker running around the room.
The hard part of the quest will be to grab the speaker. Wait until it stops moving for a bit and approach it. Once you are next to the speaker, press L1/LB to pick it up.
Next, you will have to gather the rest of the speakers and the subwoofer from other parts of the city. Most of them are easy to find, but the Downtown speaker requires an extra step.
Downtown Speaker

Once you start on the quest, head to the Field Office and speak to Langston. Discuss the matter with him regarding the speakers, and he will lead you to some data that will take you to the Oldest House. Follow the quest line and make your way to the speaker. A battle will ensue at the end of the quest path, and you will get the speaker after defeating your opponents.
Setting Up the Speakers

After you have obtained all the speakers and the subwoofer, make your way back to the Auction House. This is where you will now put everything in its rightful place. Put the woofer on the floor beside the civilian. This is located in the middle of the room where the water is. The rest of the speakers should also be set up at their own designated spots within the room.
Turn Off the Speakers

As soon as the speakers begin to play, you should immediately rush to each speaker and switch them off. You should do that as fast as you can because only then will you manage to turn them all off in time. Having done that, come back to the woofer. There will be two options for you – switch it off or increase its volume. No matter which option you choose, you will get the same reward. If you want a fun ending, choose the second option.
