Question about Pioneer DJ DDJ-400

It's possible. By connecting your UE Boom to your laptop. Then you select the output in the "rekordbox" programme on the laptop under the settings, and there your connected UE Boom. That's how I did it with a soundbar. However, there is a certain delay due to the Bluetooth. So if you want to mix, the delay will probably be a problem. However, if you have a UE Boom with a 3.5mm aux connector, you can connect it to the DDJ-400 with a cable. Hope this was helpful for you.