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I connected my computer's 1/8" audio jack to my Yamaha HS8's 1/4" input. Songs sound very weak and compressed compared to my old Logitech Z4 speaker system and Mackie CR4s. Sometimes vocals are nearly silent or the bass will disappear completely.

What's so puzzling is that I tried sweeping a sine wave across the frequency spectrum and it sounded just fine - no sudden drops/rises in volume. What could cause this behavior? Does this have anything to do with balanced/unbalanced input?

None of these made a difference:

  • 2 different 1/8" cables and 1/8" to 1/4" adapters
  • Daisy chaining the HS8 off of the Z4's remote volume control
  • Plugging my phone into the monitor
  • Upgrading my computer's audio driver

I had some Mackie CR4s a few days ago and those sounded great. I'm starting to wonder if the monitor I received is defective.

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    You need to try sweeping the sine wave spatially, from left, to centre, to right. I bet it drops off in the centre; Sounds like a phase issue. – Marc W Jun 25 '15 at 13:33
  • You're right, panning hard left/right sounds perfect. I believe it's due to polarity, not phase. – Chris Wendt Jun 26 '15 at 0:14
  • I meant the loss of the mono signals in the stereo field is due to phase cancellation. Did you get it sorted? – Marc W Jun 26 '15 at 1:16
  • Yes, I sorted it out by simply panning left/right. I think the problem was that the monitor expects a balanced signal (a positive and negative channel) but instead was getting unbalanced stereo (two positive channels). – Chris Wendt Jun 27 '15 at 1:37
  • Yeah.. sort of... Glad you got it sorted anyway. – Marc W Jun 27 '15 at 5:03
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The 1/4" input on the Yamaha is a mono balanced input. The 1/8" jack on your computer should be stereo, and since the Yamaha 1/4" input is balanced then it is reversing the polarity of the right channel from the computer and then mono summing that with the left channel. Any in-phase information present in both channels will be cancelled out (e.g., bass, vox, kick, most of the time).

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As Todd Wilcox said, this is a phasing issue; you're only hearing the stereo difference. Unbalanced stereo, as used by consumer-device headphone- or line-outputs, is virtually never used in the professional sector, because it often has trouble with interference (ground loops, dimmer buzz etc.). Professional mixers or active speakers have balanced inputs instead, which work fine even if the lines are hundreds of meters long (live) or you need very low noise (in the studio). However, this only works right when you also have balanced outputs. Professional audio interfaces have such outputs, so the best solution would be to get one of those.

The second-best possibility is to make a balanced signal from your unbalanced output: this is done with a BalUn, or, as it's more commonly called, DI Box. You'll need a stereo model to convert each of the two mono channels to balanced. DIs with two RCA inputs like the ART DTI are a good fit, you can then use a cheap 1/8" to cinch cable to connect your computer. On the outputs, use XLR to the monitors, or balanced (i.e. “stereo”) 1/4" cables.

On the face of it though, you probably don't really need the benefits of a balanced line at all. It is possible to drive even professional devices with an unbalanced line, too, you just need to do it right. First break out each stereo-channel to an unbalanced mono line (e.g. with the aforementioned 1/8"->RCA cable), each of which is then plugged into one monitor with a simple RCA->1/4" adapter. You may get in some hum static this way, but probably not more than you used to have with the Logitec speakers.

  • Thanks for the suggestions - I have since gotten an audio interface with balanced mono outputs. – Chris Wendt Jun 27 '15 at 1:38

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