Even if you connect your turntable through a proper RIAA eq and pre amp you may have an issue in regards to controlling the volume of the turntable. There wont be any easy way to set the level and control the level of the turntable signal on both channels at once.

You can use the volume controls on the rear of the speakers but that is not a good option either as they should be a set and forget calibration type of thing.

A mixer or some form of level control between the turntable/preamp and the speakers may be needed.

What audio interface are you running? Many allow signals patched to their line inputs to be routed directly to the monitor speaker output patching points by way of software or a mix knob that balances between the DAW and the input preamps etc..