Help a new guy out with some weird 3 way passive x overs - diyAudio
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Old 28th March 2003, 07:00 AM   #1
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Default Help a new guy out with some weird 3 way passive x overs

ok sorry for a question prolly answered a bunch of times but it is very specific and i'm in need of help fast so i can try to impress the guy who own the local car audio shop so he will hire me.

system: jensen cd player, will not play cds
stock rear speakers
4 inch coaxial dash speakers, JVC 60 watt max
coming soon as in tuesday or so, pioneer w304c sub with profile ca400 amp which does 300x1

i know max power isn't very relevant but that is about all the info on those coaxials i have since they were given to me, other than they were 15 dollars for the pair.

i need help with making 3 way cross overs for the coaxials AND goldwood gw-206 midbasses i plan on ordering from parts express. i'm not a complete noob to audio, i know a little. anyway, i know that making 3 ways out of coaxials and a midbass never intended to go with the coaxials is weird. but at any rate.

plan: run sub to about 85hz, have the midbasses pick up from there to about 1000hz, have the woofer from the coaxial pick up from about 1000hz to about 3500-5000hz, and where ever the woofer form the coaxial stops have the tweeter pick up from there. i also plan on ditching the stock rear fill and using those channels to power the midbasses. i also plan on using foam baffles behind the midbasses with some polyfill to make about .3-.35cubes.

i need help picking the right parts to make the cross overs. i pretty much know where i want to cross everything and have modeled the midbasses in win isd along with my sub and don't want the midbasses lower than 85hz or they will go into overexcursion. at any rate, there is an inline cap on the tweeters and i'm assuming a 6db/oct slope.

so from looking at the cap and determining what it is rated at, how can i figure out what size caps and resistors i would need for a higher order cross over? like a 3rd or 4th.

oh and are even orders better or odd orders?

now my big problems are these, how do i make zobels or parallel or series notch filters to even out the impedance of the drivers at resonance and any other major peaks? also how well can i expect to even out the response of the drivers? since i know that cross overs have to be made with the impedance in mind and i was told that if the impedance changes the cross over will not act as wanted so i need to smooth them out to have as little deviations as possible.

the midbasses i have specs for, the tweeter i'm hoping i can already pick out the caps n such for higher order slopes with the help of you guys. and for finding out anything about the coaxial drivers it would have to be using a multimeter and other simple things. that and i need to know how to test the power coming out of the deck on each channel. i think zobels can be calculated using the impedance of the driver like if it is a 4 ohm speaker and using its resonant freq, but i'm not sure.

basically any help is appreciated and if i've confused anyone or everyone please ask me to clarify. thanks guys in advance.
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Old 28th March 2003, 10:33 PM   #2
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can someone please help me out?
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Old 29th March 2003, 02:17 AM   #3
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I am not sure I have understand everything because your message seems confuse. Anyway...I will try to help.

The best way to go (especially in car) is with active filtering. These days, almost all the decent car amplifier have an active crossover built-in. This is the only way to quickly achieve the best sound with minimal measurements and knowledge.

If you really want to go passive, you will have to measure the impedance of the drivers at the planned crossover point. This is essential to know that number. If you use the nominal impedance, you will have gap or peak in the frequency response. Let say you have your impedence curve (normally measured with speakerworkshop), you will be able to simulate your crossover and then determine the value of each components.

I suggest you to not go over a second order filter: stay simple if you don't have time. Zobel are essential and notch depends on the impendance curve.

I have never designed "audiophile" grade car sound system but I am sure there is a lot of factors to compensate due to the special environment of a car interior.
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Old 29th March 2003, 10:07 AM   #4
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speaker workshop is it free? is that a good program to use to incorperate cross overs with the selected speakers? if not what would be a good program where i can input driver parameters along with desired cross over types with their component values to get simulations? i only have win isd right now.

yes i know i need the impedance at the cross frequency.

will zobels completely flatten out the impedance except for the resonant impedance spike relative to the nominal impedance used to calculate the zoble? the plan so far is to use zobels on the woofers, midranges and tweeters, not the sub, the sub i will just end up using the 12db/oct active on the amp i got for it. but for the 3 ways i will be using zobels most likely along with 4th order LR i think unless i am told that is a bad idea.

and yes passives are my chice right now, i want to get them down decently before i start actives.

what about linkwitz transformers?? are they even for passives? if they are what exactly do they do and are they really usefull?
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