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In Reply to: RE: Going active on Tympani 1Ds posted by ghost4man on January 16, 2017 at 15:49:49
Nice job with the frames!
Yes, I'd use Magnepan's crossove points as a starting point. That would be 1100 Hz single pole for the woofer/midrange crossoer. The ribbon in my IVa's is crossed over at about 3 kHz with a higher-order XO. I wouldn't cross over lower than what Magnepan recommends to avoid excursions that could shorten the life of the ribbon, *however* if you are using a higher order crossoevr than Magnepan's you can likely lower it a bit.
The Neo-8's are high quality push-pull quasi-ribbon drivers and in a line can be crossed over lower than the 1-D tweeter. I'm not sure how much of a difference it would make in the setup since the 1-D tweeter was also push pull but wire, and you've redone your woofers with foil. So just an idea. If you're getting great imaging, then it sounds like you don't have a problem (I used to have 1-D's and had the same imaging problem Roger has).
Finally, Satie has pushed up the ribbon crosssover frequency on his Tympani IV/Neo-8 combination and crossed them over at 6 dB/octave or IIRC without a low pass on the midrange. But what works for him might not work for you since you're using a different tweeter. It might be worth an experment, though.
Follow Ups:
Hi mate,
Yes very nice job indeed. Obviously resolves the issue of distance between the midrange and ribbon doesnt it.
Okay did an historical search and found the following:
For 20.7s -
Low-pass (bass): 18dB Butterworth @108Hz
High-pass (midrange/tweeter): 6dB @330Hz
Crossover between midrange and tweeter is
approximately 3000Hz and is non-defeatable.
For 3.6 -
Crossover between bass and midrange is 200Hz
Crossover between midrange and tweeter is 1700Hz
Tympani IVA
Crossover between midrange and tweeter is 3000Hz
Maggie IIIAs
Crossover between midrange and tweeter is 3000Hz
It seems that XO to ribbon at 3000Hz is a fair number to work with.
What do you think based on this history. Highly suggestive that it is.
I'm not sure f the figure for the 3.6 is correct, given the fact that it's so much lower than the other specs. Did you get it off the historical table on this sie? that has some errors in it.
I do remember reading Jim Winey saying years ago that they'd tried running the ribbon at lower frequencies and had settled on the crossover they currently used for reasons of reliability. So I agree that 3000 Hz is a good starting point.
BTW, I've thought of doing what you did with the mid and tweeter in my IVa's. The closer the better an in my house they don't need the wider separation that Magnepan puts in their commercial models to maintain structural strength. But where would I ever find the time! Another project for the future (sigh).
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