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Thread: Cheap stereo speakers for prop use?

  1. #1
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Ayer Massachussetts

    Question Cheap stereo speakers for prop use?

    I tend to want to use teensy in costume props, and sometimes I want to add sound support. This means small, lightweight, and can run on a single USB battery that also powers the Teensy and people can hear it maybe 1m away. It does not need absolute fidelity, or across the room sound support. In this case, I'm not processing the sounds, just playing pre-recorded sounds. Obviously processing the sounds would be the next step up, but may be a different question.

    For mono support I can use the on-board DAC on the 3.2/3.5/3.6 and the prop shield, and for the 4.0 I can use a I2S to mono adapter with a MAX98357A chip and attach a small speaker.

    My speaker of choice tends to be this breadboard speaker, as it allows me to mount the speaker firmly, and I have less issue with wires coming off the speaker (due to movement as when I use it in a costume prop for 10 hours):

    For stereo support, I am less sure of what is the best solution.

    On a Teensy 3.5/3.6, I can use its pair of DACs, and just provide mono amplification and speaker support for each DAC.

    Or if I use the Audio Adapter, it has both line out and headphone output pins. There are various cheap speakers that take a headphone input jack and product output, usually with their own battery. The one I have has a battery, but there is a lot of cross talk if I try to power the device via the same 5v source as the Teensy. If I use its internal battery, that means I need to specially recharge that battery and I'm dependent on how long the battery last, while if I have a common battery, I can just swap out batteries as needed. Also it would be desirable have the two speakers separate, so that the user hearing the sound gets more of a stereo effect.

    So is there a simple setup to power and amplify two separate small speakers? Do I use line out or do I use the headphone jack? I believe they run at different voltages, and if so what types of changes would be needed to swap from one to the other. Is this something the audio adapter helps with? Or can I bypass the audio adapter and use straight I2S output to an I2S stereo chip?

    Or assuming, I'm using Teensy 3.6 or 4.0, would it be better to use USB output to run the speakers and use a standard USB speaker? If so, is there a cheap/small speaker people like that works with the Teensy 3.6/4.0 USB's output?

  2. #2
    Junior Member
    Join Date
    Aug 2019
    Melbourne Australia
    Some years ago I decided to build a pocket Audio Monitor for vocal training and other portable sound reinforcement applications and here's where its at:-

    Click image for larger version. 

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    The box contains 3 x 2.2 Ah lithium cells, charger (socket on bottom, 9-16v in), stereo poweramp chip from car radio, mixer, karaoke style vocal canceller, reverb send/return, line in/out. The guts out of a reverb pedal and mono bridge output didn't fit in the box.
    Oddly enough, putting it together led me to Teensy. I can see a T3.5, touchscreen, audio interface in another box although I'd stick with the car audio chip as I just plain don't like dirty class D audio amps other than for bass.
    The aluminium plate is the "heatsink". Fine for headphones, for party fun and speakers you'd need something better.
    There is another box, same size, with two small speakers. For health reasons, at times I need to use a respirator, so the Mike goes inside it, and the speakers get popped on the counter to facilitate communication with the Bank Clerk or whoever.
    Last edited by MatrixRat; 10-07-2019 at 12:12 AM. Reason: mark copy missed that bit

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