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!
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 (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!
Tags: AirDesk laptop desk, Apple Pro Speakers, external speakers, MacBook Pro, stereo amplifier
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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.
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.
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.
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?
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.
Super. I’ll keep you posted on my progress.