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Adding speakers and predicting spl increase

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  • Adding speakers and predicting spl increase

    Hello guys, another easy question that I'm asking you to guide me through. In my journey towards audio bliss I've acquired some KRK S4V4's. Without out arguing about your opinion of this choice, just know that I am seeing the benefits of wide dispersal and midrange clarity of a 4inch driver. These speakers are impressive in how low they play as well but I am missing the spl I had with my previous set of speakers. Even though the spec is 1db less (110db vs111) than the previous speaker for max spl, the musical/rms spl is lacking, though not spec'd I can only assume its around 106-107db. I had to turn my subs down from a +6db gain to 0db gain and they match wonderfully with the 4" speakers. I would like to regain that 6db. My question is that if I were to add another set of the v4s4's how much db gain could I anticipate based off of the 110 peak spl spec?

  • #2
    Each doubling of driver count gets you 6dB additional maximum output. As for published maximum SPL specs, they tend to simply take the 1w sensitivity and add to that the additional you'd get from maximum power assuming that the increase is linear all the way. It isn't, being affected by a number of factors, including but not limited to excursion capacity and power compression, so they're not at all accurate. I can't recall ever seeing a maximum SPL chart that was measured.


    • #3
      Thanks for the response! As you know, the products surrounding professional studio monitoring, are clouded in mystery, surrounding the specs of the equipment, which allows for a lot of people be to be taken advantage of. They are starting to share less and less detailed info. They've already made it common practice to NOT share rms vs peak wattage specs, all impulse response and waterfall info is usually 3rd party and you'd be lucky to figure what ohm your drivers are. I have a measurement mic and room eq wizard so I am learning how to take my own measurements but how the hell am I gonna audition all the products for free? I digress.
      i am starting to believe that all the unspecified specs are worst case scenarios so all the watt specs are likely max/peak wattage. Just makes me more opt to start designing my own gear, cheaper and better, just less pretty.


      • #4
        You will be amazed at the extra output from multiple drivers. I am using 2 PC83-8 and 2 TC9FD18-08 wired series parallel for 8 ohm easy amp load and 120 watt power handling. I will add larger speakers to cover the bass but i almost do not need it. I can get concert level with no trouble and even good organ peddle tones.
        I was tired and got tired again so now I am Re tired.


        • #5
          Thats convincing since I am a cheap skate, but I've done good so far. I built my subs which normally cost $700 retail, with the help of this forum of course. I paid ~200 for the same krk amp and woofer plus wood material and my time so ~450 bucks for 2. I just sold my krkv8s2, I bought 7 years ago, at 400 used, for 340 even more used. I used that money to help pay for the krkv4s4 new. So for another 500 I could get another set and be good for a really long time. I'll one day build another complete system from scratch and see what thats like. Already started a thread for it. =D


          • #6
            Depends if you wire them in series or parallel.

            Series = 0dB increase (+3db for 2*SD but -3dB for impedance doubling and halving current draw). +6dB for parallel (+3dB for 2 * SD + 3dB for doubling current draw due to halving impedance).

            So.. why aren't all drivers parallel wired?
            1. Low Impedance can pose a problem in the midbass
            2. You still halve the excursion for the same given SPL for either (over a single driver). so 2 in series can meet linearity goals for a certain SPL.


            • #7
              Not mentioned yet but there is a downside to multiple drivers, the change from a point source to the constructive/destructive summation in arrays that share bandwidth.
              The physical space between sources if fixed and results in an reduction in the mutual coupling bandwidth.
              "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."


              • #8
                Originally posted by billfitzmaurice View Post
                Each doubling of driver count gets you 6dB additional maximum output.
                You are only explaining a portion of it. He is not summing just the little woofers, rather is summing loudspeakers including the output from the tweeters.

                At low frequencies where the driver diaphragms of interest are within 1/4 wavelength, they sum with correlated phase.
                For two sources that is 20*log(2) = +6.02 dB

                At high frequencies where the driver diaphragms of interest are _not_ within 1 full wavelength, the sum suffers combing and the nominal among that combing is a sum with uncorrelated phase.
                For two sources that is 10*log(2) = +3.01 dB

                At frequencies in between there is a transition.
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