low power speaker question

Discussion in 'Electronics Resources' started by ashrond, Aug 12, 2009.

  1. ashrond

    Thread Starter New Member

    Aug 12, 2009
    Hey all,
    I’m working on a modification of a Bluetooth headset; I’m building a Bluetooth speakerphone. I was inspired by a similar project I saw on the internet http://www.youtube.com/watch?v=ziQvBBZniZo , however I am having a volume issue with the replacement speaker; I can’t hear anything unless I hold it up to my head. I got in touch with the guy who built the project that I took inspiration from, all he would tell me was that he used a bigger speaker and no amplifier circuit; he would not get more specific.

    I have 0.98v showing on my multi meter from the Bluetooth speaker leads.
    My question is this, what kind of speaker do I need to put on this thing to have it be audible from a few feet away? I only have 3 volts to play with so the LM386 amplifier circuit I built doesn’t have enough power to function and therefore is not an option.
    I would like to just replace the speaker, but I do not have enough knowledge on the matter to make an educated guess.

    Any assistance would be greatly appreciated!

  2. Audioguru


    Dec 20, 2007
    1V into a 32 ohm earphone produces a power of only 0.03W.
    You need to amplify the current so that an 8 ohm speaker will produce a power of 0.125W.

    But 1V is 2.828V peak to peak and an amplifier needs to have some extra power supply voltage to work. A TDA2822M amplifier IC has an output power of 0.125W into 8 ohms at clipping with a 4V supply.
  3. ashrond

    Thread Starter New Member

    Aug 12, 2009
    Thank you very much for the response, it is much appreciated!
    Luckily I have engineered a usable power source that fits in the enclosure and can provide 6v, I got everything working on the old amp IC, so now I’m going to order the TDA2822M and give that a try.