Connecting ideal speakers to PAM8403

Discussion in 'The Projects Forum' started by Shang Lin Chua, Nov 8, 2015.

  1. Shang Lin Chua

    Thread Starter New Member

    Nov 8, 2015
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    Hi guys, i'm trying to make portable speakers utilising the PAM8403 chip.
    i've been reading up on the internet that you want your amplifiers wattage to be more than the speakers, but in all cases in youtube, i've seen people connecting 15W speakers to the PAM8403. why is this the case?
    i've bought these speakers http://au.element14.com/pro-signal/abs-224-rc/speaker-20x40mm-4ohm-2w-paper/dp/1761631 , as well as the 8ohm abs-116-rc version and find they work much better (Less clipping) when 5v/1A is connected to them.

    Looking at the datasheet output power at 5v for 4 ohm gives 2.5-3.2W, which is greater than my 2W 4ohm nominal speakers. you can definitely hear more clipping than the 2W 8 ohm speaker (datasheet gives 1.4 -1.8W)

    can anyone explain where i am wrong? and why my attempt to drive the speakers is bad? or what can i do better with these speakers?
     
  2. #12

    Expert

    Nov 30, 2010
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    Because not everything you read on the internet is true. Even if it is true, it's not true for everybody, all the time.

    This specification seems wrong. Five volts into a 4 ohm speaker will allow 1.25 amps. Audio chips do not deliver amps to speakers, they deliver volts, and the speaker allows amps to flow. When the chip can't handle any more amps, the sound clips. When you turn the volume up higher than the voltage supply can deliver volts, the sound clips.

    You can definitely hear more clipping when the amplitude is turned up too far. First guess is: Turn the volume down. If you want a different answer, you need to give more information. Are you listening to music? Are you talking about clipping when the sound is lower than the other speaker? Did you know that the efficiency of the speaker is very important in determining how much loudness you get per watt? Did you know these speakers don't even have an efficiency rating? Did you know this chip can only throw 56% as much power into the 8 ohm speaker?
     
  3. Shang Lin Chua

    Thread Starter New Member

    Nov 8, 2015
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    0
    Thank you for your quick response, its given me a lot to think about! i was thinking of making a tiny portable speaker which can play music pretty loud. and yes it is for playing music! i was talking about the clipping when both the speakers are at full volume. i personally found there to be a difference when i get voltage from the computer's usb port than the voltage from my 5v/1A adapter.

    so you reckon my speakers are just bad? i didnt even know there was such thing as an efficiency rating... never seen it on any spec at all.
    looking at another speaker, http://au.rs-online.com/web/p/speaker-drivers/4318658/
    no efficiency rating at all! so should i stick to lower wattage speakers?

    please share your knowledge mighty one :D, i'm still new to electronics
     
  4. #12

    Expert

    Nov 30, 2010
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    The wattage of the speaker has nothing to do with efficiency.
    Now I see where you got the 5 volt, 1 amp idea.

    Here is an idea of the range of efficiency. The worst speaker I ever saw was rated at 78 db/watt at 1 meter of distance. The best I know of are my Cerwin Vega H-15 speakers at 103 db for the first watt. That means you would have to apply 316 watts to the cheap speaker for it to produce the sound the good speaker makes with 1 watt. See where I'm going here? The speaker makes more difference than the amplifier.

    I haven't done this for a very long time. I don't know how many speakers are sold with no attempt to tell you their quality. Personally, I wouldn't buy a speaker with quality so low that it isn't worth advertising. So, go forth and shop for speakers. I have a 5 watt guitar amplifier that can irritate the neighbors, but that might be about how badly I play the guitar. I don't expect you to put a $65 speaker that is 10 inches in diameter on a 3 watt amplifier chip, but you can surely beat those $8 speakers and stay in a reasonable price range..
     
    Sinus23 and Shang Lin Chua like this.
  5. Shang Lin Chua

    Thread Starter New Member

    Nov 8, 2015
    3
    0
    Thank you!!! i decided to give these a shot -
    http://www.taydaelectronics.com/mylar-speaker-8-ohm-1w.html
    and the results are more apparent - i'm experimenting on the TDA2822 chip as well. no clipping either. i can increase the volume but to a certain extent the music/vocals/everything starts to get fuzzy. i'm guessing that it isnt because of the noise, its because i'm pushing the speakers limits. how did you get the value of 316watts from?

    In summary: choose the right speaker for the job. the 2W as mentioned above was probably for buzzers or something.
     
  6. #12

    Expert

    Nov 30, 2010
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    db = 10 log (p2/p1)
     
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