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I'm super excited to jump in and learn more about building an external stereo speaker from an older salvaged macbook laptop. I loved using the laptop to reference how my music sounded to get a better understanding of the playback for people using their laptops to listen to music. Anyway, this laptop has finally died and I would love to repurpose the speakers within (maybe also the class d amplifiers?) and just plug an auxiliary cord and listen. I think this is a fun project yet I'm hitting walls with my understanding of circuits and reading schematics.

I envision removing the left and right speakers from the logic board as well as what powers and drives those speakers (which I believe is the class d amplifiers) I have found a schematic of these audio circuits and envision creating a circuit board containing these components. I also envision adding a 3.5mm aux input and volume knob to this circuit to input sound and control the volume.

I feel that with the directions of the schematic, adding a volume knob and a 3.5 mm aux input isn't too crazy of an undertaking. Is there anything I am missing?

Is this doable in your opinion? Also any thoughts or recommendations for this project? I feel like the learning curve on this project is extreme but I'm super excited to learn and welcome all feedback and suggestions! Thank you in advance.

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  • \$\begingroup\$ Just build/buy new ones. \$\endgroup\$
    – Andy aka
    Nov 19, 2020 at 8:32
  • \$\begingroup\$ Great suggestion! I started wondering if a prebuilt class d amplifier would "sound" differently than the amplifier within the laptop. I am trying to replicate that sound to a T so I don't mind learning about recreating the class d amplifier within the laptop. I'll provide a schematic in the morning and have some more well thought out questions. \$\endgroup\$ Nov 19, 2020 at 9:00
  • \$\begingroup\$ If you disassemble it and power on then trace the input signal and inject hum with your finger, that is generally the high impedance input. Extraction might be fun with a Dremel tool but you need the correct supply to go with the drivers to speakers. \$\endgroup\$ Nov 19, 2020 at 9:02
  • \$\begingroup\$ Have you ever used Windows/Linux on the Macbook? (it sounds hideous) macOS/OSX tunes the audio before it goes into the speaker to reduce unwanted resonances and so on (I don't know exactly what they do but, it isn't just a straight audio output. So if you are doing it for the "type" of the sound be aware you are probably not going to get the same sound as from a "regular" (i.e. running macOS/OSX) macbook. \$\endgroup\$
    – Wesley Lee
    Nov 19, 2020 at 13:17
  • \$\begingroup\$ I'd be interested to see what schematic you have and what it covers. Certainly the tablets contain a set of amplifiers from my employer which do a lot of signal processing.. \$\endgroup\$
    – pjc50
    Nov 19, 2020 at 14:47

2 Answers 2

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You also have to deal with how much of the sound comes from the speaker's enclosure.

Unless you're sawing up and recycling the relevant parts of the macbook case (or re-using the entire case as the enclosure) you're left with a huge problem determining what aspects of the case design really matter and replicating them, or tuning the frequency response of the electronics to match the (ah but how do you measure it?) response of the enclosure you're fitting them into.

This is not trivial and may be quite surprising. Not only will the precise hole pattern of the grille matter, but the designers probably accounted for acoustic reflections off the LCD screen.

Or consider what you are making as an entirely new product with its own sonic characteristics.

The subtleties can fill entire books and while a laptop's speaker will not even remotely qualify as "high quality" in that book's terms, Apple's designers will have gone to some length to make the best of the space and power they had.

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  • \$\begingroup\$ This is very important, I once had the same idea of the OP, I extracted the speakers out of the computer, they sounded really bad, It was mostly high frequency what was reproduced, also, I don't know if the amplifier had an internal equalizer attached to it to compensate, for example, the lack of bass of the speakers. \$\endgroup\$
    – S.s.
    Nov 19, 2020 at 16:40
  • \$\begingroup\$ Hey Brian, Excellent thoughts! The most perfect replica of this "Mac Sound" is having an actual laptop produce it;-) Working down from that, my hypothesis is with the same class d amplifiers circuitry, housed within the original but modified enclosure (How exactly modified TBD) will yield a sound way more similar than not. I will totally share A/B comparisons in the future and figure out different metrics to compare. I'm hoping that faithfully recreating the signal path will matter more than a faithfully recreated enclosure. \$\endgroup\$ Nov 19, 2020 at 18:59
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Extracting the audio amp part of a motherboard, let alone a laptop motherboard, is unlikely to work well. SMD circuits, multiple pcb layers and routing. Cutting it out would be like shattering a piece of glass and trying to piece together a small section again.

There are multiple schematics online for building your own amplifier circuit. Or even typical application diagrams in the data sheet for whichever amplifier IC you want to use. You can even take the schematic for the laptop and recreate it with new parts and you own circuit board. But trying to extract the actual circuit from the motherboard is beyond what anyone would want to do and not done often.

Now, if you wanted to reuse a PCI audio card or something, that might be doable. Less complicated pcb.

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  • \$\begingroup\$ Thank you Passerby. I'll post the schematic in question with more well thought out questions to help convey the stumbling blocks I'm facing. I am interested in recreating the amplifier exactly and comparing it to a prebuilt amplifier from a kit. Very exciting stuff to share and discover. \$\endgroup\$ Nov 19, 2020 at 9:02

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