Using Macbook Pro with only 1 speaker

Discussion in 'Digital Audio' started by Schmactor, Aug 7, 2019.

  1. Schmactor macrumors regular

    Joined:
    Aug 5, 2014
    #1
    I am using a single Rokit 6 monitor speaker for sound from my Macbook Pro. It is connected with a single cable from the RCA jack to the headphone jack on my mac. Do I need to change any settings to make sure the full sound is properly coming from the speaker and not just one side of the stereo sound? If I click on "mono" in the accessibility settings the sound does not seem to change. However if I go to the sound settings and move the balance slider it lowers the sound if I move the slider to the right, even if I have mono output turned on. Does this mean I'm only getting the left side of the stereo sound and not getting the full sound? How can I be sure I'm getting the full sound through a single speaker? Thanx for any help.
     
  2. xb2003 macrumors 6502

    xb2003

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    Location:
    MO
    #2
    I don't know for sure what you are experiencing, but this is my guess: what it sounds like to me is that when you enable mono mode it sums the left and right signals into one, and when you place with the balance, it's reducing one or the other sources when you move the slider. My reasoning is that when you sum two signals together, you get around a 6dB increase, and 10dB is a perceived doubling in loudness. So the balance slider is effectively decreasing the output of one of the sources and netting you less volume.

    But, it should be very easy to test if you are getting both sides. Play a song that pans the sound, like, I don't know, the vibraslap in the beginning of crazy train. If it cuts in and out, you are only getting one side.
     
  3. Schmactor thread starter macrumors regular

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    Aug 5, 2014
    #3
    Thank you xb2003. I'll file this under the "duh, why didn't I think of that" category. Lol. I found a stereo testing track on youtube and it seems that with normal settings the speaker only transmits the left side but when I turn on mono output in the accessibility settings I do get both sides. Just out of sheer curiosity I wonder why when a single cable is connected from the headphone jack to a speaker that it automatically chooses the left side. I guess it is some sort of default? The balance slider works the same whether or not I have mono turned on. Moving to the left makes no change but moving to the right either silences the sound entirely or brings it to an extremely low volume. Not an issue at all since there's no reason for me to adjust the slider, just a curious effect.
     
  4. xb2003 macrumors 6502

    xb2003

    Joined:
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    #4
    I don't know exactly what you are using for a cable, but if you are using a 1/8" (3.5mm) TRS cable to 1/4" TS cable, what's happening is that the tip is the left side conductor and the ring is the right, and it's shorting the right to ground, hence getting only the left side. If you are using some sort of a splitter cable, you should be able to just plug the other side of the split into the speaker into the right channel.

    As a side note, if you are using 1/8" TRS to 1/4" TRS, you are likely having an issue where vocals and other center-panned sounds are quieter than normal.

    Also, I have no idea if you are familiar with the standards I listed above, but if you aren't googling them should clear it up. If not, let me know and I will do what I can to help. There are so many different standards when it comes to audio, and many of them will ground something out or sum things together when used in conjunction with one another improperly.
     
  5. Schmactor thread starter macrumors regular

    Joined:
    Aug 5, 2014
    #5
    Thanx!!! If you don't mind sharing your expertise I'd love to hear more. I'm using a single cable with a basic 1/8 out of the headphone jack on my macbook pro going to the unbalanced RCA on the speaker. Would it be better if I went into the balanced TRS jack instead? What would be your ideal setup with just one speaker going from a macbook pro? Is there a better option than using the headphone jack? Which input is better on the speaker if I'm using just one? The unbalanced RCA or the balanced TRS? Or what about the balanced XLR? Is mono output my only option? Thank you again!
     
  6. xb2003 macrumors 6502

    xb2003

    Joined:
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    MO
    #6
    Sorry, I haven't been on here in a few days and missed the email.. I'm going to try and hit the fundamentals with this post. You likely know some of it based on your previous posts, but I'm going to pretend as though you don't. :)

    The MacBook Pro can only produce an unbalanced signal... in the 1/8" TRS the tip is left, ring is right, and sleeve is ground. Same goes for 1/4" TRS when it's used for stereo signals like studio headphones. The TRS on the back of a studio monitor, however, is looking for a mono balanced signal, so tip is hot, ring is cold (reversed polarity of the hot signal), and then the sleeve is still ground. XLR, in this case ("XLR" can be used for other things in audio and lighting, but that's beyond the scope of this post), is exactly the same as TRS in that pin 1 is ground, 2 is hot, and 3 is cold. 1/4" TRS and XLR are entirely interchangeable (at least in this use case), and there would be no advantage of going with one over the other (again, in this use case).

    So the MacBook Pro produces and unbalanced signal, but the monitors are looking for a balanced signal. So what does this mean? If you were to use an 1/8" TRS to 1/4" TRS cable, when the signal hits the studio monitor the signal on the ring conductor gets the polarity reversed before it is amplified. So you will have the left channel going into the speaker in phase, and the right channel going in out-of-phase. Simply put, anything that is center panned will cancel out, and everything else will sound, well, out-of-phase. To overcome this, you want to use an 1/8" TRS to 1/4" TS cable, where the R conductor from the MacBook Pro side is not wired up or simply sent to ground. The 1/8" TRS to split RCA you are using is currently doing this.

    There is no advantage or disadvantage to sending the TRS connector on the monitors (or the XLR for that matter) an unbalanced signal, as compared to using the RCA inputs. You know, aside from RCA cables often being cheaply made and going bad after little use. :confused: And if you plug in a TS connector to a TRS input, it will short the R to ground on the input and you won't have any issues if you went that route.

    The ideal setup would be an audio interface with balanced outputs.
     
  7. Schmactor thread starter macrumors regular

    Joined:
    Aug 5, 2014
    #7
    Thank you! That is a wealth of information and I believe I understand most of it. I promise to look up some of the other stuff so that I fully understand. In the mean time would you mind just summing it up with a quick recommendation? Given the fact that at the moment I can only have one speaker and will not be using an audio interface (unless you can recommend one under $20). What is the best possible cable I should purchase and use? And would this be the same situation connecting my iphone to the speaker as well? Or does that change things? I really appreciate your generous help!
     
  8. xb2003 macrumors 6502

    xb2003

    Joined:
    Jan 18, 2016
    Location:
    MO
    #8
    Sure thing, I can clarify anything too. Sometimes things make more sense in my head than when they come out of my mouth (or fingers) haha

    There is nothing really to be gained by buying a different cable if you have an 1/8" TRS to RCA cable. The Mac can sum the channels to mono and I believe the iPhone can too.

    If you really needed a cable that summed the left and right without doing it in software on the Mac, iPhone, or.. anything else. What you would need is a cable that is 1/8" TRS to 1/4" TS where the T and R connectors on the 1/8" side are both wired to the T of the 1/4" side. You would likely have to make this cable or special order it, it won't be commonly available. I would advise against this though, as you can potentially run into distortion or clipping issues and doing it in software will avoid this.

    I don't know where you are located, but if you are in an area that Craigslist has a presence, you can look for something like a cheap PreSonus or Focusrite audio interface. I see a couple near me for $25. But as with the cable, I don't know what you would really be gaining by buying the interface at this point. You'll still be running mono which will negate any positives that the audio interface will provide unless interference is the issue.

    I'd say just save up to get yourself a second monitor and a decent interface that suits your I/O needs.
     

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7 August 7, 2019