AirDesk MacBook External Speaker Mount

Tuesday, March 23rd, ©2010 Marcus Brooks
External Speaker Mount for AirDesk

External Speaker Mount for AirDesk

Since I moved, my AirDesk-mounted MacBook Pro has become my primary entertainment center. Alas, the MacBook’s tiny speakers are almost useless, so I have finally rigged an external speaker mount for the AirDesk.

I’m using a pair of old Apple Pro speakers that came with my wife’s 17-inch G4 iMac. These speakers came with a “Y” cable and a special stereo plug that only works on the G4 iMac. I simply cut off the “Y” part of the cable so I could wire the speakers separately to an amplifier.

For the amplifier, I used kitsrus.com kit #139 (available here). This is a 1W stereo amplifier module based on the Philips TDA7053A chip. For input voltage, I’m currently using a +12V wall wart. This amp/speaker combination will work with a +5V USB supply, but only at relatively low power. At 12V it puts out all the volume I want, although I should change R3 (as described in the kit instructions) to expand the volume pot’s useful range. The module is supposed to work with up to 18V supply voltage, so later I intend to try eliminating a cord by tapping the MacBook’s power cord. That will be a separate blog entry, if it works!

Speaker Mount Details

Crosspiece Mounting Details

The mount crosspiece is simply a length of 1″ angle aluminum, cut to size with a hand nibbler. I drilled and tapped the AirDesk’s plexiglass top so I could bolt on the crosspiece. (Some grease on the tap helps it cut the plastic more smoothly.) I used steel 10-32 machine screws because that’s what I had handy, but I would probably get a 1/4-20 tap and matching nylon screws if I were starting from scratch.

Close-Up of Speaker Mount

Close-Up of Speaker Mount (Note Amplifier Location)

To mount the speakers, I drilled and tapped their undersides and bolted them to the crosspiece. To mount the amplifier, I drilled panel and index holes in the crosspiece to accept the volume pot’s shaft mount. I also solidified the pot-to-board joint with a lump of epoxy putty, and encased the board in heat-shrink. The knob for the volume control came out of a junk box.

One watt isn’t a lot of power, but I like the sound of this setup with the 12V supply and Apple Pro speakers. I doubt I could find anything better in a rig this small, but of course you’re welcome to try any alternative that you like. Someday I might try to add an amplified subwoofer of some sort to round out the bass, but probably not anytime soon!

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6 Responses to “AirDesk MacBook External Speaker Mount”

  1. Floyd Wray says:

    Excellent banter. The Marcus Brooks I used to know was a genius when it came to banter. I wonder if you’re related to him. In any event, if this is you … the Marcus I used to know at BBB … a hale-‘n-hearty hello. Glad to see, we’re both still among the living, and absorbed in the unrelenting flush of technology. So it shall always be, I’m afraid.

  2. Frank says:

    This is a great idea – I may just do this… I have a fancy new iMac, but the sound quality was much better from my old G4 iMac.

  3. marcus says:

    Floyd! How are you doing? Sorry I missed your comment before; I’m still alive, but I haven’t been paying attention lately. Things have Happened (as usual). I’ll try to email you later with more.

  4. Nick Birks says:

    This is great, but as a complete novice, I have no idea where to start. Are step-by-step instructions available for detaching the Y cable and attaching the Philips chip and 12V wall wart?

  5. marcus says:

    The kit I mentioned includes a circuit board and instructions. (Currently you can download them here to see if you’re comfortable with them.)

    As for disconnecting the “Y,” I just lopped it off with a shear and stripped back the individual wires a bit for connecting to the board. Remember for this kit you don’t connect the speaker ground wires together. (The board has separate connections for all four wires.) I apparently decided the speakers’ blue and brown wires were (+) and, and white and yellow were (–). Which is which doesn’t matter, but you get better bass if you connect both speakers with the same polarity.

  6. Nick Birks says:

    Super. I’ll keep you posted on my progress.

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