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    Administrator Robh3606's Avatar
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    Passive Monitor Thread

    I started setting up to build a new system. I was lucky to be able to purchase a pair of 476Mg's and was gifted a pair of 2216Nd's by my friend 4313B. I am going to use my favorite waveguide PTH1010. It has certain advantages similar to the 2344 because it is very short and has a rapid flare compared to the other PT Waveguides and is 100x100 which works very well in my room. I started taking some preliminary measurements on a temporary baffle of the raw drivers on the PTH1010.


    It actually measures very well and has a distinct advantage over the 435Be in this application. It has a rising high frequency response which makes it much easier to set-up with systems using higher sensitivity woofers. With the 435Be on this waveguide you have to trade woofer sensitivity to get a usable last octave response. Attached are plots for the 476Be no network and 435Be with nework and raw.

    Rob
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    Administrator Robh3606's Avatar
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    After the raw measurements I looked for a suitable network and chose the 9900 which uses the 476Mg. I simplified the crossover from a Charge Coupled Network and put that into LEAP. Then I copied it and added switches so I could take out the 3 notch filters to see what each did. First is the Schematic then the network response with all the notches in place.

    Rob
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    Here is what the response changes are as you take out the notches one by one. The first is Notch 1, then Notch 2, then the Sereis Notch /HP The Blue curve shows the changes from the original circuit.

    Rob
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    The next 2 attachements show all the changes and the last is with notches 1 and 2 removed. This became the baseline for a modified crossover.

    Rob
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    Administrator Robh3606's Avatar
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    New schematic which shows the final network for now until I can take actual baffle measurements. As you can see from the previous post the response with both notches 1 and 2 removed was not bad. What I ended up doing was changing the values of the inductor and capacitor in the series HP filter and adding a low Q 1.5 notch filter centered at 1.6K. The notch took out the bump around 2 K and the changes in the HP smoothed out the response in the upper octaves.

    Attached are the results after the changes. So far they look good. I need to build up a network to see what the actual measurements look like.

    Rob
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    "I could be arguing in my spare time"

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