2 DJ controllers with a laptop?

In advance, with DJ controller, I know only moderately. A friend and I bought DJ controllers from Pioneer (DJ DDJ RB + DDJ-400) and use the program Rekordbox. We wonder if it is somehow possible to connect both controllers via a laptop. So a total of 4 decks. Does that work, and if so, how?

Theoretically, this works, practically it will not work, I guess you have to be able to program the sound card (and many other things), it can go a lot wrong, optimizing the crossfader and your cue points is as good as uncomfortable.

How about 2 laptops and a master mixer? That would be another way.

Have fun

The free DJ software Mixxx also supports working with 2 controllers. Here is the download: https://www.mixxx.org/

Then I recommend to install ASIO4ALL, then you can route both sound cards together from the controllers: http://www.asio4all.org/ Freeware.

Mixxx is the most comprehensive free DJ software available. In addition to DJ controllers, you can also work with timecode sound discs. Every sound card is supported.

Mixxx also has a recording function to record its live mix and a broadcast function. Then you can stream your live mix like a web radio station.

Mixxx is the most comprehensive DJ software available? Funny!

I meant the most extensive free DJ software

To finally answer this in detail: Rekordbox DJ currently only supports one MIDI controller reliably. The plan does not work out.

There are other DJ softwares that support multiple controllers simultaneously, e.g. Tractor Pro. The danger with very similar models from a manufacturer, however, is that both controllers output one and the same control signal for different functions, and therefore disturb the MIDI mappings or cancel. This can also be seen here: https://forums.pioneerdj.com/hc/en-us/community/posts/360005372906-Using-multiple-controllers-with-rekordbox

Whether it can work in your particular case (no matter which DJ software), vague to doubt. It depends on the concrete experiment.

More information about MIDI controllers can be found here: dj-lexikon.info/midi-controller.html

In Traktor Pro3 I sometimes use up to 7 controllers simultaneously (2x CDJ2000 NXS, 1x DJM 2000NXS, 2x Traktor Kontrol X1, 2x Traktor Kontrol F1) Basically, the idea is thus feasible. For beginners or users without in-depth knowledge works but rather not.

The sound card of a controller is never programmable. You can only set the audio routing in the software. And how do you optimize crossfader and cue points?

I can perhaps accept that.