Splitting Macbook Pro Headphone Jack for multiple Audio Output Patches

[Jorge I. Sanchez]

Hello all!

So I'm working on a play and I want to be able to use Q Labs on my Macbook to send cues to different output patches through Head[hone jack. For context, I wanna drive sound to two PA speakers and then send separate cues to a regular RCA stereo speaker hidden under a couch. I was thinking about plugging all of the speakers to mixer, then mixer to laptop, and manually lowering levels when i want sound out of PA and silence from the couch speaker and vice versa, but that's a pain in the ass. Is there a way to split the hp jack into different output patches? Or even better, a way for Q Labs to recognize different channels in a mixer as output patches? What extra soft/hardware would I need to get accomplish this? Any advice would help! Thank you!

Jorge

[Chris Ashworth]

Hi Jorge,

Thanks for your question. I’m not completely sure I am following it correctly, so I’d like to start by describing a few basics of audio concepts in QLab.

In no particular order:

One audio patch in QLab corresponds to one output device. Examples: Patch 1 can be your headphone jack, patch 2 a USB audio device, etc.

Your cues are assigned to a single patch (a single device) and then you can route the audio in the cues to any output channel of that device. So, for your headphone jack, you get two channels (stereo output). If you patch a cue to your headphone jack, then you can get at most 2 separate channels from that device.  

If you have a USB with 8 channels, you could patch a cue to that device and manipulate up to 8 distinct channels from each cue.

It sounds like you have at least three separate physical speakers you want to use. To use them all at the same time with separate channels of audio will require using more than just the stereo output of your headphone jack, since that has only 2 channels.

I’d recommend reading through the documentation on Audio cues here:

http://docs.figure53.com/qlab/audio/

In particular the Device & Levels docs:

http://docs.figure53.com/qlab/audio/#device-levels

which includes a video describing how the matrix mixer of the cues works.

At the end of the page you’ll also find an overview of the audio signal flow through QLab:

http://docs.figure53.com/qlab/audio/#audio-signal-flow

best,

Chris

[Dominic Hargreaves]

The other question, especially if equipment is limited, is whether
the PA feed needs to be in stereo. Often a mono feed split to both
(either paralleled at the amp, or via a mixer) will solve this
issue without compromising the production. So you would feed the
FOH mix to output 1 (left) and the FX speaker to output 2 (right).

Of course, there are other good reasons to use external devices -
even a cheap USB interface will provide more reliable results in a
theatre setting, with a balanced output.

Cheers,
Dominic.

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[Mark Valenzuela]

For context, I wanna drive sound to two PA speakers and then send separate cues to a regular RCA stereo speaker hidden under a couch.

I was thinking about plugging all of the speakers to mixer, then mixer to laptop, and manually lowering levels when i want sound out of PA and silence from the couch speaker and vice versa, but that's a pain in the ass. Is there a way to split the hp jack into different output patches? 

What you’re describing is one of the basic functions of Qlab - sending different sounds (in the form of audio cues) to different speaker channels. The problem you’re running into is that the headphone jack is only 2 channels (a left and a right), which means that without doing what you described manually with the mixer, you only have the option to send different audio to two different places. 

Or even better, a way for Q Labs to recognize different channels in a mixer as output patches? 

When you talk about Qlab recognizing different channels of the mixer, and therefore being able to control them, what you’re really wanting is NOT an external mixer that the headphone jack plugs into (because you still have the problem of only being able to send 2 channels of audio), but what you’re wanting is an audio interface with multiple outputs. There are many on the market, and there is a lot of good information on this listserve in other discussions on the best ones, but once you have a USB or Firewire interface with multiple outputs (6-10 is typical) then Qlab will recognize that device and be able to send your sound cues to each output individually. This would allow you to have that many speakers in the space, and send them all different audio. 

Having 6-10 channels may be overkill for you, but this is the answer to your question about whether Qlab can recognize different channels on the mixer. In your particular circumstance, if you wanted the PA speakers to receive only one signal (so the music would play in mono, not stereo) you could set your PA to receive audio from channel 1 of the headphone out, and your couch speaker to receive channel 2 of the headphone out. But unless you want to control a mixer manually, you will be limited to just 2 channels. 

Do yourself a favor and buy a decent quality USB or Firewire interface. It will sound better than the headphone jack, and will give you several descrete channels to play with. 

Good luck,

Mark

Mark Valenzuela

Sound Designer

(c) 502.727.7049

markval...@fastmail.fm

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