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Old 3rd February 2002, 03:54 AM   #1
Bose(o) is offline Bose(o)  Canada
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Default Crossover design

Finished the speaker design choices, now it's off to the hard part for me....I'm foreign to crossovers. I got some calculations on a Third Order two system...
C1=386.1mf
C2=1158.3mf
L1=27.1mh
L2=55.6mh
L3=18.5mh
C3=772.2mf

Here is the site http://www.globalnode.com/users/stevenr/spkrs/
let me know if you need more info, drivers, etc.

Couldn't I go with a more simpler xover??? How do I decide on the order things???
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Old 3rd February 2002, 08:59 AM   #2
griff is offline griff  Australia
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hey bose, im as new as u in X/o's and would like to know what the speaker drivers, cabinet etc that u are building.

thanks
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Old 3rd February 2002, 05:19 PM   #3
CHRIS8 is offline CHRIS8  United States
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Please remember that those are the formula, that while accurate...must be used considering for the acoustic response of the driver and it's frequency dependant resitance (impedance). In reality, those equations are only the electrical crossover frequencies. They could only be used in real life if you had a nearly resistive drivers with flat frequency responses extending 2 octave or more past the intended cross point. While such drivers do exist, you would have to search for them and then pay an arm and a leg to actually aquire them.

You will need to plot impedance, measure freqency response, sensetivity of the drivers on a test baffle(the same size as the intended finished design) and then design the initial crossover design with that data. This is not pratical to do manually today. Use computer program such as Speaker Workshop to speed up the processes. http://www.audua.com. There are of course others, but this one is free.

After you have reasonably accurate data and have a design to start from, then order your parts.

Another option is to make active crossovers, and provide a dedicated amplified channel to each driver. You may find some pro gear xovers useful, as many have infinite variable xover frequencies and digital delay to account for time/phase alignment..this would definately make things almost too easy.

Also, don't forget to account for baffle step when designing the crossover, or correct it at line level(much better IMO).j

All of the information that you need to make your own active crossovers as well as baffle step compenstion can be found at: http://sound.westhost.com

Of course, there are many other issues but it is not practical to even mention a small fraction of them. You really should do more research before building a design from scratch as to minmize your costs and trouble. You can find some good links from the main 'Speakers' link on the home page of diyaudio.com to get you started.

Why don't you build a predesigned DIY speaker first, then you can have a reference point and play with the crossover values in it, change the box tuning, etc. in order to get your feet wet.

Build something cheaps first, like the Dayton projects at: www.speakerbuilder.net

Have fun.

-Chris
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Old 4th February 2002, 08:53 AM   #4
navin is offline navin  India
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the values look awful big. just recheck your data.
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Old 4th February 2002, 10:15 AM   #5
griff is offline griff  Australia
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does the X/O seem reasonable??

bass cutoff = 45
tweeter cutoff = 2910

L1 = 40.014 mH
C1 = 625.22 uF
L2 = .309 mH
C2 = 4.83 uF

its a 2nd order 2 way filter using seas h624 and audax tw025a16
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Old 4th February 2002, 12:10 PM   #6
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The value for bass looks a 32 Hz filter Butterworth (Q = 0.707),
on the nominal 5.7 Ohm DC res. of the Seas, have not the Audax data but the values you provide looks like a Butterworth around 4200Hz

Just one curiosity: what is the practical use of such a x-over?

sandro
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Old 4th February 2002, 08:34 PM   #7
griff is offline griff  Australia
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it was the values winISD gave me
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Old 5th February 2002, 05:50 AM   #8
navin is offline navin  India
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cutting off bass below 50Hz is rather difficult to do using passive crossovers. trust me I tried. why do you want to limit bass to 45Hz?

I tried to limit bass (using a 1st order passive) to aa 6" woofer (ScanSpeak) and found that it was not required the XO offered little protection.

If you are building a 3 way or your midbass is very limited in the bass then you can move the XO point upwards (80-100Hz would be better).

If you want to limit bass to the entire system use a bass blocker cap/network available readymade with RCA plug attached at www.crutchfield.com.

Hope this helps.
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Old 5th February 2002, 07:54 AM   #9
griff is offline griff  Australia
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Default HELP ME!!!!!

hmmmm, please help me, ive got no idea

can u plz recommend me a Xover, im really stuck, im an extreme beginner, this is my first project, as i said above, i am using the Audax TW025A16 tweeter specs and the Seas CC17RCY H624 specs

thanks in advance for your much needed help, it will be a 13.5l box, studio moniter styles, any help would be much appreciated, values and design etc.
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Old 5th February 2002, 10:59 AM   #10
navin is offline navin  India
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rules of thumb.

XO should be aprox 2 times resonance freq. of tweeter.

as a start stick to 2nd order corssovers. they offer enough protection and are not too complex.

The way I see it the woofer you arre using would prefer to be crossoed over at about 3k and 110hz. The 100hz is because the Sd (area) and Xmax (mm) are very small.

You will need a 8 or 10" woofer to fill out the bottom unless you want a system that is extremly limited in SPL.

You may try starting with a low Q (Linkwitz Riley 2nd order) with these drivers at 3000Hz. See if you like that and then work from there.

hope this helps.

Regards
Navin
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