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DIY Speakerbox

Discussion in 'General Electronics Discussion' started by mikebrady, Aug 17, 2014.

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  1. mikebrady

    mikebrady

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    Aug 17, 2014
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    You will need an amplifier.
    The signal provided to an auxiliary input jack is usually very small. Far too small to drive a speaker with any decent volume.
     
  3. mikebrady

    mikebrady

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    Aug 17, 2014
    Ah, i see. Could you recommend an amp?
     
  4. mikebrady

    mikebrady

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    Aug 17, 2014
    I imagine i'd use an amp like they use for sub setups in cars
     
  5. Gryd3

    Gryd3

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    Jun 25, 2014
    That would be overkill :D

    Do you want to build your own amplifier to use, or would you rather buy a pre-made one to wire in?


    Edit:
    https://www.sparkfun.com/products/11044

    You will need to provide power to the device as well.
    There are many kinds of amplifiers available as well. Some being more efficient but more difficult to build.
    If you are buying one pre-made that is not much of a concern. (Class-D is usually more efficient, and will allow a battery operated device to last longer.)
     
    Last edited: Aug 18, 2014
  6. mikebrady

    mikebrady

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    Aug 17, 2014
    Haha, well...for the sake of my inexperience, we shall go with a pre-built.
     
  7. mikebrady

    mikebrady

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    Aug 17, 2014
    Okay, awesome. D'ya think a nine volt battery would do it as far as power goes?

    There's four speakers, all the same type
     
  8. Gryd3

    Gryd3

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    Jun 25, 2014
    You may need a larger amplifier to drive 4 of those little suckers.
    The link I provided will only give you 1.4W which will work, but is not very much.

    Pick your battery carefully. What you want is something close to the desired input for the amplifier. If the voltage needs to be changed too much, you will be wasting power in the conversion.
    Take a browse on a couple Wikipedia Pages.
    It shows the capacity for a Zinc 9V battery to be roughly 400mAh which translates very roughly into 3.6 Watt Hours. You could expect no more than 2 hours with the amplifier I linked.
    AA Batteries on the other hand have a capacity of 1000 - 1500mAh for Zinc (Alkaline almost double). Two AA Zinc Batteries would provide anywhere from 3 - 4.5 Watt Hours which is comparable to the single 9V battery. (I don't know about you, but I'd rather buy a big pack of AA than a pack of 9V)

    You also have the option to use rechargeable batteries. The capacity is less, or you could put in a little extra work and use a Lithium rechargeable battery built into your project. You could simply plug it into a USB charger to charge it up. It's no uncommon to find Lithium batteries at 1800 - 3600mAh ( 6 to 13 Watt Hours )

    Let us know what you want to accomplish.
     
  9. mikebrady

    mikebrady

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    Aug 17, 2014
    Well, volume>battery life.
    I'd be satisfied with two/three hours of battery life, i'm probably going with rechargeable AA/C batteries to save da monah.

    From what you've told me, i'm gonna want an amp with a higher wattage.
    http://www.adafruit.com/products/17...Of3GFzcSTv0kYII9_NhcYz035m8ilhnW5aBoCERnw_wcB
    I like that because it's got the jacks already soldered in and 20 watts per channel should get me the volume i'm looking for. (music for small get-togethers, going out on the porch for a smoke etc)

    I'm just trying to consult those more knowledgeable than myself. If you concur that the linked board will work for my purposes, then i'll order the parts and work with you and others to figure how to wire up the circuit. I'm gonna want to throw an on/off switch in there too. But beyond that, that's just about it.
     
  10. Gryd3

    Gryd3

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    Jun 25, 2014
    This would work for you pretty well if you don't want to build from scratch ;)
    I'm sure that 20W will be more than enough for you ;) Of course as volume goes up, battery life goes down.
    How are you with audio equipment? That amp says it can drive 8 or 4 ohm loads.
    I am unsure what your speakers are, but remember that running them in parallel will usually reduce the overall load.. (ie, 2 8ohm speakers paired will be 4ohms. So you could do 2 speakers per channel)
     
  11. mikebrady

    mikebrady

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    Aug 17, 2014
    My bass amp is 8. Ohm and runs a 10 inch 35 watt speaker, i figure i'll be fine. I planned on running 2 per channel anyhow.
    I build pc's but as far as audio equipment and wiring and such, im pretty new.

    Okay, imma order the parts. Now the waiting game.
     
  12. BobK

    BobK

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    Jan 5, 2010
    Do be aware that the power you can get out of this depends on your battery voltage. Use 12V if you want to get anywhere near 20W. I calculate that the max you can get from 12V is 18W. At 6V this would go down to 4.5W. Both are into a 4 Ohm speaker. For 8 Ohm speakers reduce by a factor of 2.

    Bob
     
  13. Gryd3

    Gryd3

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    Jun 25, 2014
    Good catch BobK, I did not put in the effort to calculate how that would scale with a lower voltage. If a lower voltage were to be used, I figure a boost converter would be acceptable to compensate?

    "20W Stereo Output (4Ω, VDD = 12V, THD+N = 10%)"
     
  14. BobK

    BobK

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    Jan 5, 2010
    Much better to use the voltage of battery that you need. A boost converter would just waste power.

    I would use 8 D cells to run this. At 20W they should last about 6 Hours.

    Bob
     
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