Problem with monitors --> phase inversion???

Discussion in 'Monitoring' started by Burgundia, Jul 16, 2010.

  1. Burgundia

    Burgundia Guest

    Just got a shiny red pair of KRK Rokit G2 6s, but I don't have an interface yet so I tried to connect them directly to my Mac Pro. They came with male/male TRS cables so I picked up a couple of TRS to 1/8" converters and used an 1/8" Y connector I had lying around to plug them into the line out port in back, and then changed the sound settings to send sound output to the line out port.

    Played a couple of songs, and every one had muffled main vocals and non existent bass...this of course made me think of phase inversion, so I decided to do a little test. I imported one of the songs into Audacity, split the stereo into 2 separate tracks, ran the phase inversion function on one of them and converted to mono. Sure enough, the resulting sound (played through my headphones) was exactly what I'd been getting through the KRK Rokits with the original track.

    So, is the problem just that I need an interface, or is it possibly something more serious? I got these used off CL, and they sounded fine when I tested them through their previous owner's setup, although he did have a Presonus Firewire hooked up. (For the record, the problem didn't go away when I tried the headphone jack in front.)
  2. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
    Home Page:
    No, the problem is in your Y-cable. The monitors have balanced inputs and you are feeding these from a L-R stereo signal, so what you are hearing through the monitors is the difference signal. This is mainly stereo width information, and central sound sources such as vocals and bass will be attenuated.

    Instead of a parallel Y-cable, what you need is a lead that splits a 3.15mm stereo plug to 2x mono (unbalanced) signals - the monitors are quite happy to take unbalanced signals. If your Rokits have RCA inputs as well as TRS jacks, then a lead such as the 10' version of this gives the correct functionality, but you may need to split the RCA ends back to near the 3.15mm plug to get the physical separation to reach the speakers.

    This will get you working within the limits of what your internal sound card is capable of. For the next step in improving the sound quality, you should focus your attention on getting an external USB or FireWire audio interface.
  3. Burgundia

    Burgundia Guest

    Thanks, Boswell! I just remembered this morning that I have an L/R RCA to 1/8" cable on my dvd player, so I borrowed it for the Rokits and they worked fine. (Whew!) I'll check Radio Shack for the stereo to mono split.
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