depends on if the powered speaker has more than one input.

But if you're using Serato, you could just set the program to mono output and use a single cable.

Depending on how you configure the mixer's L+R outputs into a single speaker, you may experience some phasing issues with any of the recorded music's center panned instruments/vocals.

Using the mono output within Serato like DJ Soo suggested is probably best your best bet.
And then run only a single cable (either L or R) into the speaker.

Also depends on what exactly you are trying to achieve here...

Not a big deal. I'm just trying to add a third speaker to my setup. If i just used 1 channel, would it make this channel too dominant in this setup ?

Thanks for the help

If one stereo channel being more dominant than the other is a concern then mono is the best solution. FYI, mono is almost always the best solution for dj purposes.

I've been using both L+R booth out to powered speaker (Yamaha DBR) for a monitor. Seems ok. The speaker has L+R RCA inputs so I guess it's made to run both channels.

So, if I ran my track mono to the first speaker and daisy chained the other two from it, I will have the same input on all three.. right? will serato combine left and right tracks in mono mode?

Thanks

Sorry, What I mean is will serato combine left and right tracks to mono in real time instead of me having to convert all my tracks to mono?

YES JUST go to settings>mixer tab in serato and switch from stereo to mono, nothing major :)
jonguerrera.com

yes

Thanks so much everyone