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Old 25th September 2013, 09:10 PM   #1
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Default FAST Xover question...

Hello

I have a FAST setup with a set of FF85WK's...right now I am using a minidsp between my pre and amps set up for 250hz...but I was wondering if I could just use a simple cap setup on the Fostex's instead??

This would be used for when I go back to my integrated (preamp outputs but no main in's for the loop)...

I would want them cut off below 250hz like I have it now...thinking a 50-70uF cap should do the trick...yes no??

Thanks!!!
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Old 25th September 2013, 09:37 PM   #2
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sure a passive cap at speaker level could do the trick of HP well enough, but that's the last place I'd want to use any type of EL cap, and a decent film at these values could easily run $20-25 a piece
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Old 25th September 2013, 11:41 PM   #3
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What box is it in? There's a very good chance there's a large impedance peak around 100hz give or take. So, no, a single cap won't work. You'll want an LCR impedance flattening circuit or go second order.

If the impedance peak is very mild, you could possibly get away with it.

Oh and ya, the cost won't be cheap.
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Old 26th September 2013, 02:09 AM   #4
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Ouch!!

I built a uFonken for the 85's...and although I've run them free range and blended in the helper woofers with the mini...running both through the mini sounds way better!!

But then I can't use the one amp I like because there are no main in's...

Oh well...it was a thought

Thanks!!
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Old 26th September 2013, 02:41 AM   #5
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Just do it second order. What's the harm. I can give you some basic components.
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Old 26th September 2013, 10:25 AM   #6
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Nothing I guess LOL!! I was even thinking PLLXO but amps will change therefore the xover will as well...I want this to be somewhat stable??
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Old 26th September 2013, 10:47 AM   #7
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Don't forget to low-pass filter the woofer.

Can you stick with the mini DSP or make a dedicated active crossover? Otherwise it's a big step backwards really.
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Old 26th September 2013, 10:59 AM   #8
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I am doing that now but I would like to bring back in my Electrocompaniet amp...unfortunately it only has preamp outputs...

That and I was considering a tube build...a Get*Set*Go or a Budgie or something like...maybe with those I can do a preamp-out\main-in setup to be used with the minidsp...

Right now I brought out my little ASL EL84 pre along with my Virtue Audio tripath amp to run the 85's...I have a Parasound for the bottom end that does a good enough job...

All that gets to be too much cabling and gear...would like to simplify things a bit!!
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Old 26th September 2013, 03:44 PM   #9
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Passive is certainly simpler. But costly. What woofer are you using? I've done a few passive FASTs and they have all ended up in the same ball park of second order on both drivers with the polarity reversed. About 4mH and 50uF on the woofer and 30uF and 3mH on the full ranger. Or there abouts.
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Old 26th September 2013, 04:11 PM   #10
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If you go passive, consider a series XO.
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