# need help to identify crossover points and slopes (schematic inside)



## Veedo (Sep 29, 2009)

this is an alpine spx pro crossover. i cannot find much info about the details of this crossover, strange, because it seems quite popular. if anyone could tell me the crossover points/slopes for the tweet and woofer, that would be huge. thanks.


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## Veedo (Sep 29, 2009)

no takers huh? can anyone point me in a direction that would help me figure this sucker out? i cant be the only one that would like to know!


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## XtremeRevolution (Dec 3, 2010)

At minimum, people will need to know the impedance of the tweeter and driver. 

Posting this on techtalk.parts-express.com might get you more help. We design crossovers for home theater over there, so you'd get more help there.


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## Moon Track (Mar 10, 2011)

Crossover point is a quite relative term..
Low pass filter has 1st order, with all switches disabled it is tuned at 950Hz . 
With enabled J3 -1300Hz. 
J2 decreases quality of the filter (order). 
J1 is Zobel network , it decreases output from speaker at high frequencies starting from 4-5kHz .
Twitter network:
With shorten J4 the C3-L2 it is a second order for 3500Hz . Without J4 , third order and tuned a bit lower. Principally it is all. Resistors are for twitter attenuation.


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## Veedo (Sep 29, 2009)

hmm it wont let me edit my original post to put in the driver/tweeter info that i plan on trying with the crossover, so here they are. if anyone is interested in seeing the stock alpine speaker specs for which the crossover was designed for, they can be found in this pdf http://support.alpine-usa.com/products/documents/OM_SPX-17PRO.PDF here 

*Woofer*
Specifications 
Brand Peerless 
Model P830961 
Nominal Impedance(ohms) 4 
Power Handling RMS(Watts) 75 
Power handling Peak(Watts) 150 
Usable Frequency Range(Hz) 40-3000 
Magnet Weight(oz) 18 
Voice Coil Diameter 1.25 
Thiele & Small Parameters 
DC Resistance(Re) 3 
Mounting Information 
Overall Diameter 6.5 
Largest Diameter 7.125 
Bolt Circle Diameter 6.6875 
Baffle Hole Diameter 6 
Magnet Diameter 4 
Depth 3.375 
Mount Depth 3 

*Tweeter*
Brand Vifa 
Model 25CAR 
Nominal Impedance(ohms) 4 
Power Handling RMS(Watts) 75 
Power handling Peak(Watts) 150 
Usable Frequency Range(Hz) 1.8-23K 
Sensitivity(dB) 92 
Sheilded Magnet Yes 
Voice Coil Diameter 1 

thanks for the help moon! the woofer is passed at 1300hz? doesnt that seem a bit low? tweeter is around 3.5khz? is there a way to calculate the slopes too?


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## Moon Track (Mar 10, 2011)

It’s only 1st order (6db per octave). The order speaks about slope. The only difference is the type (Linkwitz ,Bessel,Butterworth ),it determines the shape of round part of the FR curve where the crossover point actually is.
There are more players than only filter and speaker resistance.
Speaker needs in less power to create the same level of acoustical pressure at higher frequencies, and these 1300 Hertz are pretty virtual. 
Those guys already played with this crossover. 
Google Tõlgi
Look at comment and graph with number three. It’s translation from Russian.
There is said that the LP settings do almost nothing for FR. Main changes are from HP settings.


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