On my Macbook pro, I have 2 inputs and 1 output. One input is the internal microphone, and the other is the physical line in jack. The single output is the physical output jack.
I do not think this configuration will work with a second external microphone as it is presented without the use of external sound hardware. Some changes to the aggregate device selections and subsequent sound input and output settings would be required. I'm sure it will work, but I do not have external hardware to test and document on.
In order to achieve full duplex using the latest intel mac and mac os X (10.5.6), you have to open the Audio Midi Setup application either through the Utilities menu from the Finder or if you already have SoundSource installed you can open it from the SoundSource menu.
From there, you select Open Aggregate Device Editor, and hit the little square PLUS button to open the list of hardware devices available for aggregation on your system. For this tutorial we will be using an aggregate device that is composed of the internal microphone, the line input and the line output. Check each of these in the hardware list, and then give the device a name - I called my aggregate device allthree.
Hit the Done button and close the window to save your settings.
Sound Flower (http://www.cycling74.com/products/soundflower)
Important *ensure* that you reboot after installing SoundFlower/SoundFlowerBed the first time. This makes sure that the software is properly hooked into the operating system. This is a good practice whenever installing any audio hardware, as the system may be unable to complete the installation if any applications are using the audio hardware in exclusive mode - until the system is rebooted.
SoundFlower is a software mixer that can aggregate any sound sources into a single logical stereo output pair, or in systems with external hardware, to a logical 16 channel output bus. For this tutorial we are assuming no external active electronics. The only external hardware used here is a stereo mini-jack y splitter, and a stereo mini-jack male to male cable.
The Y splitter is plugged into the line out on the laptop. Your headphones are plugged in to one side of the splitter, and on the other side of the splitter, the cable goes from that split to the line in jack on the laptop. This creates the physical sound loop that gets around the intentional crippling of the OS audio control software implemented by Apple (you CANNOT select pass thru on the aggregate device editor) to keep from being sued by the RIAA. (<-- conjecture)
The main interface for interacting with SoundFlower is the companion application SoundFlowerBed, which installs itself into your menu bar in the upper right and looks like a little flower. This is simply an interface to control SoundFlower itself.
SoundSource and LineIn (http://rogueamoeba.com/freebies/)
SoundSource
This allows you to change your system input, output and most importantly DEFAULT output. The default output is what is used for all audio in any program that does not provide and interface to change its own sound output - thus the default output is used in any such software.
When you use SS to set the default input, output and system output, it should change the relevant settings in the system preferences Sound control panel. If things don't work, make sure this is the case and if not, set the Sound control panel to match the settings in SS.
Line-in
This program adds the missing THRU feature that is intentionally disabled in the Sound Control Panel. This forces the audio to mix on the external wiring. if Apple had not disabled the thru checkbox, mac users could easily combine their internal audio hardware without difficulty. After many, many, many tests I determined that there is absolutely NO WAY to combine the internal microphone with the output due to the disabled thru checkbox.
LineIn solves this issue. You select input from as the aggregate device, and output to soundflower (ch2). The thru button couples the microphone over the external wiring into the mix. As a side note, the Pass Thru button acts as a mic mute, if you deselect Pass Thru the internal mic is removed from the stream.
This mixes everything, itunes, camtwist movie player vid+audio, skype, sound effects from garageband into your line IN as well as your headphones. I prefer to have my own voice in the output channel as a monitor, so the use of allthree including the internal microphone is fine by me. Your mileage may vary. Connected physically this way, the audio delay is 200 milli-seconds or less and does not distract me very much, it is like playing a small venue on stage - you can adapt to the delay.
I used an aggregate device that has all three in it called allthree (internal mic, line in and line out). Think of soundflower like the place you plugin all the things you want to hear, "main out" in stereo land.
Soundflower takes the inputs from wherever, soundsource lets you set the default system and main outputs to soundflower, line in lets you use play thru (which is grayed out in menus in the aggregate device editor!) to combine the line in to the line out.
SoundSource output set to soundflower (2ch)
SoundSource sound input set to the aggregate device you want to use
SoundSource system set to soundflower (ch2)
In the sound panel from system preferences, make sure the set output to soundflower (2ch)
set input to the same as soundsource aggregate device
I set the sound effects to soundflower (ch2) but this plays sounds from skype etc to the audience. This may be changeable, but I havent played around with it since I got it to work I wanted to capture the proven operable settings first.
in audio midi setup
default input set to the same input aggregate as the other two
and default output and system output should set by soundsource from before, default to soundflower (2ch) and system to soundflower (2ch)
