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How to? Determine overall wattage between multiple drivers & Crossover.

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  • How to? Determine overall wattage between multiple drivers & Crossover.

    I've been trying to figure this out for a 3 way system.

    The "easy answer," though I suppose has to be mathematically incorrect is that "you just have to use the wattage of the lowest powered driver."

    My best guess would be to meausure the total resistance on each channel, including crossover and driver (ignoring the variable impedance), and allocate percentage of overall power "refused" by the resistance of that channel. Then recording the wattage of that channel by the inverse of that percent.

    Is there something in VituixCAD I'm overlooking that gives me this information?

    Can anyone throw down some hints so I can start heading in the right direction?

    Thanks

  • #2
    Look at the woofer power handling. That will be the true determining factor as the woofer uses most of the input signal. But there is a catch. The thermal rating is nearly always higher than the mechanical handling. Meaning the driver will breach Xmax before the thermal rating of the coil. And power handling of a raw driver is always listed as the thermal.
    https://www.facebook.com/Mosaic-Audi...7373763888294/

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    • AllisterMcRae
      AllisterMcRae commented
      Editing a comment
      Ok. Got it. Niggly bits I'll have to put in a memorable note somewhere. Cheers

  • #3
    Originally posted by AllisterMcRae View Post
    The "easy answer," though I suppose has to be mathematically incorrect is that "you just have to use the wattage of the lowest powered driver."
    Easy, but incorrect. The midrange and tweeter don't receive as much power as the woofer. That's because the power density drops by 3dB with each octave increase in frequency. On average with 500Hz and 5kHz crossovers the woofer will see 75% of the total power, the midrange 20%, the tweeter 5%.
    In terms of how much power is safe use speaker modeling software to determine the power to the woofer at xmax. You can use more, for added amp headroom. You can use less, but at the risk of high THD if you play louder than the amp can cleanly deliver.


    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • AllisterMcRae
      AllisterMcRae commented
      Editing a comment
      Ok. Sounds like a rule of thumb along side the handy notes about power density. To your point on XMax, I think I'm going to have learn how to more effetively use vituixcad. At 1 Watt, its maxing out the Morel UW1258 with 4V at 1kHz. Thanks for the pointers.
      Last edited by AllisterMcRae; 01-13-2023, 07:58 PM.

    • billfitzmaurice
      billfitzmaurice commented
      Editing a comment
      It would take around 1kv to reach xmax at 1kHz. In the low frequencies 60-70v would be a reasonable figure.

  • #4
    Originally posted by isaeagle4031 View Post
    Look at the woofer power handling. That will be the true determining factor as the woofer uses most of the input signal. But there is a catch. The thermal rating is nearly always higher than the mechanical handling. Meaning the driver will breach Xmax before the thermal rating of the coil. And power handling of a raw driver is always listed as the thermal.
    ^This. You can model this in WinISD. I once put a 6.5” driver in a huge 1.4 cu ft box cuz it modeled well in to 30’s or some such. But it was pointed out to me that it could only handle something like 5 watts before reaching Xmax even though the thermal power handling was 30 or 50 watts.

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    • #5
      Originally posted by AllisterMcRae View Post
      Is there something in VituixCAD I'm overlooking that gives me this information?
      Enclosure tool will provide you with output limitation by driver excursion. Then view menu - > power dissipation for power consumption of each component. Default setting of PN > 2kHz is good place to start for part sizing.

      I'm not deaf, I'm just not listening!

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      • #6
        Originally posted by billfitzmaurice View Post
        Easy, but incorrect. The midrange and tweeter don't receive as much power as the woofer. That's because the power density drops by 3dB with each octave increase in frequency. On average with 500Hz and 5kHz crossovers the woofer will see 75% of the total power, the midrange 20%, the tweeter 5%.
        In terms of how much power is safe use speaker modeling software to determine the power to the woofer at xmax. You can use more, for added amp headroom. You can use less, but at the risk of high THD if you play louder than the amp can cleanly deliver.

        What do you think about an RS100p for a mid covering 400 to 4k in a high spl speaker? The specs say 30w rms. Might need two of them in a tmmw. Possible woofer is RS270p. Woofer power handling is 100w rms. Sub would be used below 60hz. The potential speaker owner wants about 110dB at the seats with metal music.

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        • billfitzmaurice
          billfitzmaurice commented
          Editing a comment
          Without even doing a simulation I can tell you it won't do that. With 87.5dB/w sensitivity it won't exceed 107.5dB at 1 meter with 100w Pe. I also question why you'd use a driver with 23Hz Fs if it's going to be used with a sub, and why you'd run a sub to only 60Hz.

      • #7
        My question was mostly hypothetical about the mid, not the woofer, and was inspired by your comment in post three.

        I thought a tmw 10" 3-way might have the needed output, but I did not do the math to see how much power would be needed to get there. I was assuming maybe 128w. Per your post, that would be about 96w to the woofer, and about 25w to the midrange. Whatever spl that works out to would be about all that could be expected from a tmw. I don't really think a single RS125p would be enough, so I was thinking maybe two would be better. So tmmw as an option, would have about 13w to each mid.

        You ask why use the RS270p. Well, I have one, and like it. The distortion measures pretty low. It works well sealed in a small box, and with a 60hz high-pass, I don't think excursion is an issue. It could be high-passed at 100hz, but I think subs sound better crossed lower. Just my opinion. I know there are exceptions. Crossing higher may be necessary for someone wanting to play this loud. The other reason for the driver choices involves sims. I could use the Dayton factory data very easily.

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