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determining passive crossover for bullet tweeters

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lycantheleopard View Drop Down
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    Posted: 17 April 2012 at 2:01am
so, i have an idea for a horn/multi tweeter set up in one cabinet.  how would one go about picking the right parts to spec a highpass xover at around 9 khz?  any tutorials?
 
this will go above a 2 inch driver that likes a big eq shelf above ten khz so i'd love to try this idea.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2012 at 6:05pm
  The way my top boxes are configured is the 2" is connected directly to the speakon, the amp powering them is then crossed over at 1.5khz on the LMS, the 1" is then connected through a 6khz pass filter and then the speakon so the 2" receives 1.5khz and up but the 1" only receives 6khz and up. If you only need a simple high pass filter then off the shelf units are pretty cheap but if you to build something custom type 'crossover calculator' into google and have a look what you find. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lycantheleopard Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2012 at 8:23pm
yeah, all i need is a highpass, probably could get away with an off the shelf unit but most i've seen dont really go as high as i want, will do some looking around again today, its been awhile since i checked out the offerings available.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2012 at 10:14pm
Determine the final impedance of the bullet array.. typically 4 or 8ohms depending upon how may are series/parellel connected, and then build a textbook 1st or 2nd order crossover for it.. which will be just a capacitor or an inductor/capacitor pair. http://www.the12volt.com/caraudio/crosscalc.asp#cc

Edited by Conanski - 17 April 2012 at 10:15pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 1:38am
So you want a passive crossover from 2" to 1" at 9k after the LMS?
 
If you have a 2" DC coupled, then add a 1" via a passive xover you will have a phase error of 90 degrees per capacitor in crossover average, depending on crossover state (etc) above 9K.
 
If you had a passive on the 2" and 1", then time aligned via the LMS the pahse shift would be =. For the HF.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lycantheleopard Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 1:58am
this is true, but how audible would that shift be up so high?  there is nothing stopping me from using a crossover from the 2 comp driver to the tweeters, just figured i wouldnt really have to as i'd be managing its frequencies etc outside the box.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 2:18am
Well, Mike from San Jose, I could argue all day with such parameters.
 
However at 9k and at your altitude (343M/s)  you would have a full phase shift every 38mm( Frequency dependant). Thats 1.5" to you, so negligable. I personally would treat each HF devices  as = though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lycantheleopard Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 9:12am
if your taking my honest slightly newbish questian as an argument then you've got much bigger fish to fry.  read carefully before assuming things good sir.
 
using a passive highpasscrossover on the 2 inch comp driver in conjunction with whatever the lms might do would also create phaze error, which the lms could correct for, but what if i'm going all analog? what then should i do
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 9:59am
Thats easy Mike. Just use 2 passive, like mentioned previous 1st or 2nd order.
 
If so this simple online calculator will be accurate enough;
 
 
You will just need the HF portion, x 2
 
If you wish to roll off the 2" you will need the HF and Mid section  ( band pass) of a 3 way
 
 
Personally I would use LR 2nd order 12dB/oct. Simple and effective.
 
Thats without getting technical and calculating using octaves etc. However as with anything else in sound it is subjective and personal. As long as you like it, then it is good. Smile
 
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 2:40pm
I would reccomend anyone who's getting into building passive crossovers to use LIMP (Loudspeaker Impedance Measurement Progaramme) and an "ARTA Box" which together will generate a very accurate graph of impedance vs frequency for any system and  thus allow you to properly design filter networks based on real impedances rather than nominal ones. The box also allows the electrical phase and frequency response of the completed filter to be measured using ARTA. http://www.artalabs.hr/
In this case the difference between nominal and real impedance is likely to be small, but if you were arraying up several bullets the errors could add up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lycantheleopard Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 7:59pm
thanks all for the help.  i was trying to go for the "dont put anything between your power and your driver if you dont have to" approach but i think i will give this a try.  i actually already have the 800 hz crossovers for the 2 driver, just need to wire up a cap or two across the pair of bullets going above it.  that calculator should do me nicely.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Muckerbarnes1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2012 at 9:43pm
The caps to the bullets will go in series. Caps alone will be 6dB roll off at best. This is one place where an inductor makes a difference. Either way, its all fun.
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