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  • Adding Sensitivity

    Quick simple question.
    If you wire two drivers in parallel how does this effect Sensitivity. Say your tiring to match woofers to mids and you wire two 8 ohm 90 db woofers in parallel. Do you get a Sensitivity of 90 at 4 ohms or will you get something a little higher like a 92 db at 4 ohms.

    Thanks for your help,
    Ed

  • #2
    Re: Adding Sensitivity

    96 db at 4-ohms at 1w/m

    Comment


    • #3
      Re: Adding Sensitivity

      If the 90-dB sensitivities of the 8-ohm woofers were measured with a 2.83-volt input, which happens to be a 1-watt input, wiring them in parallel will result in a sensitivity of 96 dB with a 2.83-volt input across their 4-ohm impedance, which is a 2-watt input.
      Paul

      Originally posted by stephed View Post
      Quick simple question.
      If you wire two drivers in parallel how does this effect Sensitivity. Say your tiring to match woofers to mids and you wire two 8 ohm 90 db woofers in parallel. Do you get a Sensitivity of 90 at 4 ohms or will you get something a little higher like a 92 db at 4 ohms.

      Thanks for your help,
      Ed

      Comment


      • #4
        Re: Adding Sensitivity

        If you double the cone area (i.e. wire two speakers), you get +3db.

        If you halve the impedance while the voltage stays the same, then suddenly 2.83v goes from 1 watt at 8 ohms to 2w. Since you doubled the amp power, you get +3db.

        +3db from doubling the cone area +3db from doubling the amp power = 96db
        DARPA Jr - 2015 InDIYana Winner - RS180-8 + RS100P-8 + ND25FA
        The Aria's - RS150-4 (or RS150-8) + XT25SC90
        The Mariposa's - TEBM65C20F-8 + ND16FA
        The Canzonetta's - RS100P-8 and ND16FA
        AudioSource AMP-100 Mods OR Pyle PAMP1000 Mods

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        • #5
          Re: Adding Sensitivity

          Thanks a lot that really helps.

          Thanks Again,
          Ed

          Comment


          • #6
            Re: Adding Sensitivity

            http://www.audioholics.com/loudspeak...-basics-page-2

            I found this closer to reality when I did measurements with several combinations. Although my results were higher. Depends on the amp too. Would rather use actual measurements than elementary school math.

            Comment


            • #7
              Re: Adding Sensitivity

              For the post graduate course on sensitivity gain or loss check out my white paper starting on page 17.

              NFLAWP.PDF


              Jim

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              • #8
                Re: Adding Sensitivity

                It's easy to figure for a stand mount speaker. The woofers on a floor standing speaker really need to be measured to see how much boundary reinforcement you are getting from the floor.
                http://jaysspeakerpage.weebly.com/

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                • #9
                  Re: Adding Sensitivity

                  Originally posted by ngjockey View Post
                  Would rather use actual measurements than elementary school math.
                  I didn't realize they were teaching logarithms in elementary school nowadays.

                  Comment


                  • #10
                    Re: Adding Sensitivity

                    Originally posted by 1100xxben View Post
                    I didn't realize they were teaching logarithms in elementary school nowadays.
                    LOL, here in New Mexico its not even part of 10'th or even 11'th grade math track. In fact it's a rare student who hasn't had calculus who I encounter that has even heard the term. Of course the problem extends to businessman and politicians as well who have no concept of how things grow (or decay).

                    Comment


                    • #11
                      Re: Adding Sensitivity

                      Originally posted by stephed View Post
                      Quick simple question.
                      If you wire two drivers in parallel how does this effect Sensitivity. Say your tiring to match woofers to mids and you wire two 8 ohm 90 db woofers in parallel. Do you get a Sensitivity of 90 at 4 ohms or will you get something a little higher like a 92 db at 4 ohms.
                      That depends on what you use for a signal level. If it's 1 watt you'll get 93dB. If it's 2.83v you'll get 96dB. It's usually best to use voltage sensitivity, not power sensitivity, when making calculations.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

                      Comment


                      • #12
                        Re: Adding Sensitivity

                        Originally posted by 1100xxben View Post
                        I didn't realize they were teaching logarithms in elementary school nowadays.
                        Presuming that was factious; unfortunately I have heard adults say that Algebra had NOT been a requirement for them - The concept of formula reduction was baffling; along with the relevance to the real world.
                        Last edited by Sydney; 12-23-2014, 11:24 AM. Reason: gr
                        "Not a Speaker Designer - Not even on the Internet"
                        “Pride is your greatest enemy, humility is your greatest friend.”
                        "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                        • #13
                          Re: Adding Sensitivity

                          There are many adults that can't do even simple math, like addition or subtraction, in their heads, for instance to "make change", much less multiplication or division or percentages. Helps explain why so many people can't budget and amass huge debts, like from credit cards.
                          Paul

                          Originally posted by Sydney View Post
                          Presuming that was factious; unfortunately I have heard adults say that Algebra was not been a requirement for them - The concept of formula reduction was baffling; along with the relevance to the real world.

                          Comment


                          • #14
                            Sad but true

                            There are many adults that can't do even simple math,
                            That reality is a serious issue - my opinion
                            "Not a Speaker Designer - Not even on the Internet"
                            “Pride is your greatest enemy, humility is your greatest friend.”
                            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                            Comment


                            • #15
                              Re: Adding Sensitivity

                              Originally posted by 1100xxben View Post
                              I didn't realize they were teaching logarithms in elementary school nowadays.
                              Interestingly, I was just reading where a young mathematician has recently solved an Erdos Conjecture on gaps between Prime Numbers. It involves the following equation:

                              There are enough Logs in there to build a fire. ;)
                              Last edited by Jeff B.; 12-23-2014, 07:42 PM.
                              Click here for Jeff Bagby's Loudspeaker Design Software

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