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      12-31-2011, 07:00 PM   #120
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Drives: '08 335i
Join Date: Jul 2008
Location: JAX

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Originally Posted by cdgatti View Post
Kai , can we use this modelling to predict what the best crossover points would be for the various woofers?
I'm not sure I'm qualified to answer that question.

What I usually go by, and what has worked best for me in the past, is to go by ear. I would shut off the subwoofer and keep lowering the x-over until I either hear distortion and/or a sharp drop-off near the cut-off point. Then I would raise the dial up a notch or two. Once I have found that point, I leave it there for a few days and listen to all sorts of music, at various volume levels, and make sure I'm happy with it. Then, and only then, I bring back the sub. Generally speaking, the x-over point should be above the driver's Fs (resonance frequency) but some drivers may actually work slighty below it. Keep in mind, the Fs is where the driver will want to play with beaucoup distortion! (the enclosure can sometimes help the driver play below the Fs, and keep distortion in check)

On the other end, the cutoff frequency is actually determined by the door midrange's ability to play as low as possible. So you do the same thing, this time only play the doors and shut off the woofers and sub. This time though, because it is a free-air installation, you want to stay comfortably above the midrange driver's Fs.

In my case the Morel woofers have an Fs of 38Hz and I am crossing them over at 55Hz with a 12dB/oct slope. The Legatia midranges have an Fs of 113Hz and I have them high-passed at 150Hz with a 24dB/oct slope.
Mobridge DA2 > JBL MS-8 > ARC XDi 600/4 > JBL Gti 408 Mids & Vifa OT19 Tweeters; PG Ti2 1600.5 > Morel HCW-10 & IDMax 15