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  • ND90-8 BSC filter

    I want to build a boom box similar to the Sprite by Paul C. However I want to make the baffle 9" instead of the 6" his design calls for. The volume will be kept the same. I still want to have the flatter response of using the BSC filter, but I know it needs to be different due to the wider baffle. I don't know exactly how to calculate for the filter myself. I messed around with some online calculators and maybe got close, but I may be way off too? I don't have any modeling software either...

  • #2
    Using Tolvan's "Edge", it looks like widening the baffle will only alter BSC SPL by about 1dB.
    I'd try it as-is.

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    • #3
      I would build it as is also. Room placement will likely impact BSC more than the increase in baffle.

      Additionally, you may want to look at the ND91-8, a newer version of the ND90. It models well in a much smaller enclosure. I built a soundbar with each driver in a 160 sq. inch ported enclosure (6" Long x 1" ID port) and it sounds great. Instead of passive BSC, I used the EQ settings of the amplifier to boost the bottom end.

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      • #4
        Thanks for the info guys! I'll give the original filter a go and see how it sounds.

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        • #5
          Hi... I have posted this in another thread too.

          I am planning a Sprite build with a bit of a twist. I had done a Sprite build last year using the filter. It sounded big. The only issue was that I was not satisfied with the top end response. So, now I'm planning the Sprite build as separates, each ND90-8 in a separate box 1/2" stock with outer dimensions of 8H x 5W x 11D, with the same filter and am adding an 89db 8 ohm AMT tweeter with a 9db L-Pad. The crossover will be 1st order at 9000Hz.:

          1. Should the low pass filter (1st order 0.15mH coil) be placed in series AFTER or BEFORE the BSC (0.9mH coil and 20 ohm resistor in parallel)?

          2. Should I just avoid the low pass filter and run the ND90-8 full range as they anyways start dropping around 9000Hz-10000Hz.

          3. Is 9db attenuation on the tweeter good enough or there would be a need to increase the L-Pad to compensate for the loss of sensitivity on the ND90-8 due to BSC.

          Please note that I already have the 0.9mH Inductor and 20 ohm Resistor.

          ​Thanks in advance.

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          • #6
            Originally posted by Chenevert View Post
            I would build it as is also. Room placement will likely impact BSC more than the increase in baffle.

            Additionally, you may want to look at the ND91-8, a newer version of the ND90. It models well in a much smaller enclosure. I built a soundbar with each driver in a 160 sq. inch ported enclosure (6" Long x 1" ID port) and it sounds great. Instead of passive BSC, I used the EQ settings of the amplifier to boost the bottom end.

            Did you have issues of port noise with a 1" port? Also, does the ND91-8 have similar low end compared to the ND90-8? Did you use any High Pass filter on the ND91's to avoid them bottoming out?

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            • #7
              bsl100 -- I did something similar

              see here
              http://techtalk.parts-express.com/fo...pepper-boombox

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              • #8
                Originally posted by ceiol View Post
                bsl100 -- I did something similar

                see here
                http://techtalk.parts-express.com/fo...pepper-boombox

                Hi ceiol.... Thanks for the link. How is the load on the amp. It must be seeing a load lower than the rated minimum 4 ohm.

                Now, if I wanted to use the same filter as the Sprite for the ND90-8 (I already have the coils and resistors), and cross over to the AMT-8 tweeter at 9000Hz with a 1st order crossover, how / where would I add the 0.15mH coil on the ND90-8 with respect to the BSC filter.

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