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Dayton ND90-8, Aura NS3 notch filter help, please

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  • Dayton ND90-8, Aura NS3 notch filter help, please

    Hi Gentlemen,

    As I continue to tinker around with XSim trying to get a more intuitive feel for it, I have been trying to come up with a filter that will supress the 8db peak at 6.2K that these almost identical drivers show when I measure them in Chris R's Pico Neo single driver cabinets. Paul Carmody developed a filter for this driver as used in his Sprite design, but it did not actually flatten the peak, but rather rolls off the upper mids and boosts the bass. I'm not sure it is actually possible to significnatly reduce the peak which starts at 4.8K rises to +8db at 6.2K and is back to the 4.8K level at 7.4K. I'm guessing that what I'm looking for is a 2.6K wide 8db deep notch if such a critter exists and can be built with passive parts. If it can in fact be built, I would sure apprecite finding out what it would look like.

    Thanks!
    Jay

  • #2
    Try this (why I'm in italics is unknown at this time!),
    a small 0.05mH coil paralleled by about a 13uF (or 12uF) cap, inline w/the driver.
    In my sim, it chops the 8dB peak by about half w/out adversely affecting the rest of the region. (The best I could get w/a simple (2-3el) filter.)

    To move the "notch" up in freq., make either the coil or cap smaller (larger values push it lower).

    These values could change depending on whether you've got other passive parts in the driver's filter, OR (if you do) you might be able to add parts to THAT filter to get about the same results.

    This is basically an LCR filter w/the "R" being infinite (there is no R). If you use some lower values for R (like 20 ohms?) you lose the sharpness (narrowness) of the notch w/out any improvement.

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    • #3
      http://mh-audio.nl/Calculators/parallelnotchfilter.html

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      • #4
        You CAN use a generic notch filter program, but I used your observations along w/actual impedance data for the NS3/ND90-8.

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        • #5
          Thanks Guys! Very informative and helpful. I'll be putting the filter in one of my Neo Picos and comparing it to the other. I like the NPs a lot as they are, but since I can measure now I can't resist seeing how they sound without that big 8db peak. I will report back here in the next week or two.

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          • #6
            Originally posted by Drjay View Post
            Thanks Guys! Very informative and helpful. I'll be putting the filter in one of my Neo Picos and comparing it to the other. I like the NPs a lot as they are, but since I can measure now I can't resist seeing how they sound without that big 8db peak. I will report back here in the next week or two.
            Let me know how it goes! I may use in my Pasobaric 490 build.

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            • #7
              DrJ, if I remember right, which I might not, Mr. Carmody mentioned in his "Sprite" build, he was trying hard to keep his filter simple and cheap as possible, and still get decent sound quality. I thought he did a decent, if not "ideal" job. I'm morally certain, a more complex "notch filter" could work even "better", but at what cost?. You could make a fine two-way MT from the little Aura NS3 and one of the new Peerless tweeters, but it won't be dirt-cheap either. It should make a nearly ideal compact computer near-field relatively low-output (plenty for me!) monitor, pushed by no more than say a 35 WPC amp.
              Enjoy your experiment, and let us know how it works out.

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              • #8
                Hi Drjay. I attacked this issue completely differently. Instead of notch filters and such, I chose to just cross it over below the peak to a cheap tweeter, the ND16FA-6. I used LR4 acoustic slopes at 4.5 kHz. Of course this approach almost doubled the total driver/parts cost but I feel the end results were well worth it. The little ND90-8 does exactly what it's good at and the cheap tweeter sounds a ton better above 4.5 kHz than the woofer ever could. And now off-axis response is very good too!
                Craig

                I drive way too fast to worry about cholesterol.

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