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crossover component formulae

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odc04r View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2017 at 9:00am
Best way is to look them up in a reference design table as a modification to the standard formulae you mentioned in the first post.

If you want to know where they come from then draw out the transfer function of a series LC lowpass filter, you will get a result with a polynomial on the denominator. This structure is what all more complicated filters are broken down into, because it is the basic filter building block. Ok a 1st order is really the simplest, but with one pole only you can't manipulate it as much.

Once you have the polynomial (coefficient of the s^2 term should be one to be in standard form). The coefficient of the linear term can then give you the Q factor of the filter. So if you want a certain Q and Wo, you reverse engineer from this point to get your L and C. Or you can just look them up as you did!

More reading here, Matlab (or Scilab=free) is very handy for evaluating filter designs and generating nice visual plots. Python is probably quite good too, not used it myself for this purpose.

Edit - Forgot link

Edited by odc04r - 13 March 2017 at 10:32am
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LunchieTey View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LunchieTey Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2017 at 10:48am
Best way to design any crossover is build the box, install drivers and THEN measure with a calibrated mic.

Then SIMULATION of crossover designs using these curves will get you 95% there seeing as off axis plots are very important. A flat on axis response only can still sound like utter garbage that can't be eqd out.

This of course needs to be listened to as a flat curve may still have nasty sound thanks to drivers etc.

Using this method I turned basic plastic passive speakers into very high performance passive boxes that have no brand name etc and are very low key(and cheap by comparison)

Edited by LunchieTey - 26 March 2017 at 10:51am
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