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Reload Thread: 3 dB

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    khi's Avatar
    khi
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    3 dB

    whussup all?

    I was at futureshop today, and I was talkin to the Install Manager, oneof the only guys I've talked to at future shop that seems to know his stuff. We got talking into ported enclosures...and i said I was under the impression that porting a box, would give you approx. a 3 dB increase. What he told me was that a 3 db increase is almost doubling the loudness, from what it was sealed, such as that if you heard a car that was 150 dB, and then one at 153 dB the 153 would be twoce as loud as the 150

    is this true? Im very very curious to know.

    thanx

    p e a c e
    k h i







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    evo2k3's Avatar
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    yup....thats true.....the decibal scale is logrithmic, to find out how many times louder 1 spl is and another, you simply move the deimal 1 place to the left and use that number as the power of 10 your raising...for example 150 and 153.......(10^15.3 / 10^15.0) = 2 times as loud....make sence?



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    SoundsUnlimited's Avatar
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    Thats not a real good pay of showitng that..cause its not really TWICE as loud as it formally was! So you should go back and tell him he is full of ****!! Cause a 3 decible increase is very noticeable but 140 to 143 is not twice as loud! For an example your mirror may not vibrate and then with a 3 decibel increase it may start vibrating then!! Now when u start getting about 6 or more Decibles, now this is when it starts to get Twice as loud!! But I think his way of showing u that was just stupid!! I have been to shops before and they will tell u some off of the wall bull **** such as he did!

    Blake




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    Uhm, well.. Everything I've ever heard or read says that 3db is equal to a 2x increase in pressure. Since our perception of volume is based on the pressure exerted on our eardrums, a 2x increase in pressure would seem like a 2x increase in volume to us. However, I don't think that our ears are really properly tuned to correctly register it, because most music we listen to varies in volume throughout, and unless you just listen to sine waves all day, getting your ears to correctly determine db changes on a small scale is **** near impossible. (hope you all followed my rather long sentance)

    Just because it doesn't sound like it's 2x louder doesn't mean it's not.



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    i have always heard that it is twice as loud
    Last edited by 91lacdeville; 03-16-2003 at 04:33 PM.




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    Yea usuyally a 3db increase. You can also gain another 3db by damplifying your trunk. Now a 6db increase would be very noticable.



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    Originally posted by SoundsUnlimited
    Thats not a real good pay of showitng that..cause its not really TWICE as loud as it formally was! So you should go back and tell him he is full of ****!! Cause a 3 decible increase is very noticeable but 140 to 143 is not twice as loud! For an example your mirror may not vibrate and then with a 3 decibel increase it may start vibrating then!! Now when u start getting about 6 or more Decibles, now this is when it starts to get Twice as loud!! But I think his way of showing u that was just stupid!! I have been to shops before and they will tell u some off of the wall bull **** such as he did!

    Blake
    what the hell have you been smoking....i dont care about audiable difference, I just showed him how the scale works....the move of the decimal place changes decibals to Bals...that scale is still logrithmic....therefore base ten raised to the quanitiy of bals gives you output, to calculated how many times louder, its simply a ratio of the larger spl value over the lesser spl value.....no matter where you are on the scall 3db's IS ALWAYS twice as large. My god man, take a physics class. By the way what the hell is a Decible? it decibal.....in reference to the Bal scale. Your explaination is **** poor to say the least.



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    yeah the other day while i was testin my system, i had a 3 db differnce... i could tell it was louder, but not by a whole lot.. normally i was hitiin around 149 150, testin it out was at 152 153, . i dont know if it double the power, but all i did to get to their was turn my bass up fro the Hu to 0 rather than -3..



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    CarAudioAddict's Avatar
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    To get a 3dB increase in volume you have to DOUBLE the power of your system.

    If you are hitting 150 dB with 2000watts, then to hit 153 dB you need 4000watts.

    Now this doesn't always apply either. If you buy subs that have more excursion but the same rating, the dB level will increase slightly (not 3dB but it will increase)

    As for it being 2X as loud, thats wrong. While there is a very noticable differencein volume, it is not twice as loud (maybe close though)



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    if you really want to measure "SPL" get a barrometer. the difference between 150 and 153 is double, thats the way decibals work, its not volume though so stop saying loud, its rapid changes in air pressure which the ears interpret as sound. so actually, the air pressure is twice as great with every three decibal increase, you can hear the difference. but it wont be like if you turn the volume up halfway.




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    evo2k3's Avatar
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    Originally posted by Grand AMature
    if you really want to measure "SPL" get a barrometer. the difference between 150 and 153 is double, thats the way decibals work, its not volume though so stop saying loud, its rapid changes in air pressure which the ears interpret as sound. so actually, the air pressure is twice as great with every three decibal increase, you can hear the difference. but it wont be like if you turn the volume up halfway.
    thats a good point....we should be saying there is twice the pressure....the rest is still correct......so unless SoundsUnlimited wants to show his face on this thread again, i think we can rest assure that 3db's is 2x the pressure.



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    correct me if im wrong, 2 subs sealed = 1 sub ported, assuming there are the same sub. This doesnt sound right to me



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    Originally posted by actlsub
    correct me if im wrong, 2 subs sealed = 1 sub ported, assuming there are the same sub. This doesnt sound right to me
    nope




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    Originally posted by SoundsUnlimited
    Thats not a real good pay of showitng that..cause its not really TWICE as loud as it formally was! So you should go back and tell him he is full of ****!! Cause a 3 decible increase is very noticeable but 140 to 143 is not twice as loud! Blake
    Uh, yes it is. Every 3 db is twice as loud as interpreted by the human ear.



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    well ive tried to stay out of this one.....but it appears that people are not giving correct info......the fact of the matter is that every time u increase by 3db's the human ear interprates it as 2x as loud.....im w/ mylar and everyone that has said this......peace




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