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  • dkalsi
    replied
    Thanks Scott/Chris - I actually ended up checking with another forum member who had built the speakers and they also confirmed that the couldn’t not hear any port noise despite blasting the system at insane volumes. Sent from my iPhone using Tapatalk

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  • scottsehlin
    replied
    In practice, I have found the LithMTM to handle power quite well. One of the applications I use them for is larger outdoor gatherings. They aren't very sensitive, so I run them with a pro amp - but they can bring the party to the neighborhood without noticeably straining, which is impressive for their size. Chuffing hasn't been a problem with the PE 1.5" flared port. As Chris mentioned you can probably go with a 2" port to be safe, but the fit will be a little tight and I don't think you will need it.

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  • Chris Roemer
    replied
    If you're not comfortable w/1.5"d x 4", go w/2" x 8".
    (I used a 2-1/2"id port on my "ntns".)

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  • Chad2
    replied
    Awesome build!

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  • dkalsi
    replied
    I have parts on hand to build the Lithium MTMs - but wanted to know if anyone who has built the design experienced any port noise? Utilizing Mr. Bagby's Woofer Box and Circuit Designer spreadsheet, predicted port air velocity is 38m/s at 43hz with just 15watts of system power. At 35-watt system power, the woofers would be reaching their x-max, and at that point, predicted port velocity is 58m/s. Now I understand that the prediction is for a sine wave signal, and audibility will be much less with music - but still, 58m/s at 35 watts (or even 38m/s at 15 watts) seems awfully high.

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  • woodsart
    replied
    Re: LithMTM

    Originally posted by scottsehlin View Post
    There has been a request to show how I laid out the crossover. I used a separate woofer and tweeter board with the tweeter board mounted to the rear of the cabinet (on standoffs from a biwirable terminal cup) and the woofer board mounted to the bottom. Instead of opening them up to take a picture, I thought it would be easier to follow if I sketched out a quick diagram. Gray circles are mounting points.
    Thanks Scott, these crossover pics are fantastic and necessary for the "speaker builders" that have no Schematic knowledge!

    Thanks for taking the time,

    Robert

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  • scottsehlin
    replied
    Re: LithMTM

    There has been a request to show how I laid out the crossover. I used a separate woofer and tweeter board with the tweeter board mounted to the rear of the cabinet (on standoffs from a biwirable terminal cup) and the woofer board mounted to the bottom. Instead of opening them up to take a picture, I thought it would be easier to follow if I sketched out a quick diagram. Gray circles are soldering points.
    Attached Files
    Last edited by scottsehlin; 11-19-2014, 10:06 AM. Reason: typo

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  • joeybutts
    replied
    Re: LithMTM

    Thanks Scott!

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  • scottsehlin
    replied
    Re: LithMTM

    Confirmed: It is a 1" offset.

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  • joeybutts
    replied
    Re: LithMTM

    that's fine, my woofer holes are a bit wider than your drawings, just wanted a ball park. Feel free to double check for the sake of updating the schematic. I can't wait to get this thing going!

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  • scottsehlin
    replied
    Re: LithMTM

    I think it is 1" offset from the center line. I know that is very close, but will verify tonight.

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  • joeybutts
    replied
    Re: LithMTM

    Scott! One last question (I hope!). What is the offset of the tweeter? Thanks!

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  • scottsehlin
    replied
    Re: LithMTM

    For the woofer inductors, I used an 18 ga. steel laminate core as the preferred tradeoff between size, cost, and dcr. I had some 1.6's in my parts bin - I suspect they came from Madisound (but a long time ago). I wouldn't worry about using 1.5 mH - it's within tolerance.

    The resistors will have some impact and I just noticed that PE doesn't have those. I bought an assortment of resistors in that range as part of a larger order from Erse, so that is where mine came from. Meniscus is a good source, so don't hesitate to go with them. As previously mentioned, they will do custom inductor values as well.

    I will bring mine to Grinnell this year.

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  • joeybutts
    replied
    Re: LithMTM

    Meniscus also has the 13 ohm resistor. Double score!

    Thanks again guys! Another project to get done! :D Then on to one that has been on the backburner a LONG time.

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  • joeybutts
    replied
    Re: LithMTM

    Thanks fellas. I was hoping to keep all the parts at PE if I could..... But if I should get one from Meniscus I will bite the bullet.

    Thanks for the help gang!

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