crossover question(s)

[will33]

Little background.

Been using my SM400S to biamp an alpha6 with various woofers I have around here and been really liking it but...that amp, my only head that's "standalone biampable", has recently bit the dust so it's time for passive crossovers.

Keeping this relatively simple and affordable and as an added benefit, greenboy's done a lot of this work already. I can read impedance curves, punch values in a calculator, etc. I understand corner frequencies are going to move some when the coils heat up etc.

In this "cheap but good" 2nd order Linkwitz, http://greenboy.us/fEARful/crossovers.htm#CheapButGood the highpass section makes total sense to me as does the inductor on the lowpass but why is the lowpass shunt double or more the value the calculator calls for? Protection against short at higher power levels, some phase thing? I know it's there for good reason, read the write up on over-damping etc. but I don't get it.

FWIW, my woofers run in the neighborhood of 7ohms at a 700-800 corner frequency and not 10+ like the woofer in that example.

I guess the question is do I need a bigger shunt? Should I get one to be better or safer. Or doesn't it matter seeing as the biggest displacement limit on the bottom half of this thing maybe 200 watts.


Edit: FWIW it's worth, what I've got so far is 2nd order Linkwitz, high side 9.5ohms, low side 7ohms, cross frequency 730hz.

That gives me:
C1 - 11.48uf
L1 - 4.14mh

C2 - 15.58uf
L2 - 3.05mh

Like I said, C2 is confusing. Found this article http://sound.westhost.com/lr-passive.htm#s2.0 that has formula for figuring impedance rise as it relates to heat but still need to run the formula for my woofers. I don't have a lot of test equipment to measure all this stuff here so the more figuring beforehand the better, although there is a place in town here that can do these measurements for me if needed.

[greenboy]

Forget the calculators. Start working with driver data for specific drivers in specific enclosures. The calculators are a travesty for the infirm. See Passive Crossover Designer & other loudspeaker design software - widely referenced in knowledgeable circles to really open up your understanding - and frustration at not having your own measurement test suite;}

Linked here: http://greenboy.us/fEARful/#links

Great designer guys that have many thousands of bux in other tools use Jeff's software, and he has many decades of cred as a heavyweight in speaker design. Also read like crazy and use that google. Forget about slopes and third order this second order that and BW and LR because it's all just an approximation construct that fails to address the realities you will find.

[will33]

This one. http://audio.claub.net/software/jbabgy/PCD.html

Let me dive off into that for a while.

Playing one-way speakers sure sucks after you get used to the mid thing. Should've been doing this years ago, thanks.

[will33]

Main reason I say Linkwitz is the mids fs is plenty low enough for 2nd order and I absolutley do not want any bump at this crossover frequency, it's right in the nasal/honk area of the bass to my ear.

[greenboy]

I think Jeff still might look into various audio forums, but primarily around Parts Express forums did I see the most in-depth Jeff posts when I was grubbing.

[greenboy]

Hey Will,

I've often thought that you might be a guy who'd want to continue to dig in. If you just want to solve one particular problem well rather than shoddily, it can be frustrating to have to delve because there is much to learn just to do one crossover that hits the mark. Or misses, for that matter.

But if you want a little more to be fascinated by, that program in conjunction with another that can take Eminence-supplied driver datapoints for frd and zma and give you in-enclosure datapoints in sim ... going down this path can really give you some new answers as well as some new questions.

It had another effect on me however: I realized I couldn't stand the amount of time it took to cover all the bases for a series of designs, when with my own measurement equipment I could really zoom along during parts of the design process and not have to work from so many different angles to feel confident in the resulting designs.

If I were to design commerically, I'd need some LEAP or Smith & Larson stuff at the minimum (you can construct a test suite for less but it's deficient in some areas), which is cheap compared to years ago, and fun, but still requires some financial commitment. But in some of the enthusiast forums you can find many tens of people who have done just that for a HOBBY, and they are interesting people indeed.

[will33]

I do like to dig in. As far as time, I'll need this stuff in a month or 2. You guys are an incredible resource here and although I'm miles ahead of where I was as far as understanding how all this stuff works, it's the old "the more you learn, the more you realize how much you don't know" thing.

[greenboy]

It only gets worse, will33. You can get married to it ; }

And then, you still need to balance it with other creative endeavors and life demands. And mastery is tough for any of them, a lifelong pursuit really. But it seems like one side feeds the other. Some of it can be beneficial to actually making cool sounds and moods before you realize you need to go out and shovel the walk or get a jump start after the gig and do something about that faulty wiring harness ; }