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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Speaker Nominal Impedance or DC Resistance for Xover Calculation posted by diyxover on October 20, 2005 at 17:24:08:
Unless your woofer has very low inductance and a fortuitous response curve, it's a good idea to use a zobel to stabilize the impedance so that the crossover works as predicted. The inductive rise from the woofer's voice coil can largely negate the effect of a simple crossover.On a midrange driver if the inductance is low enough you can possibly use the published nominal impedance, but once again a zobel might not be a bad idea.
On a tweeter, as long as you're crossing over well above resonance, impedance compensation often isn't necessary. But in some cases you get a resonance between the crossover components and the driver that can negate the effectiveness of a simple crossover.
If you want a peek into some of the issues that can make simple "textbook" crossovers fail to perform as expected, take a look at the "PiSpeaker Crossover Document" accessible through the link below, authored by Wayne Parham of PiSpeakers.
Then there's the issue of what's happening phase-wise between the drivers. I've seen crossover component value changes move the response in the opposite direction from what you'd expect, due to the effect of shifting driver phase interactions. Getting a passive crossover "in the ballpark" isn't necessarily too difficult, but really getting it right is far from trivial. Having observed a professional designer at work on a crossover, I can tell you it's a far far cry from what I could ever accomplish with my copy of The Loudspeaker Design Cookbook, a radio shack SPL meter, and a pink noise disc. That being said, once the professional designer was done, several well-educated, experienced listeners commented that they could not hear the crossover even on such revealing program material as violin and cello bowing.
My years of amateur speaker building convinced me that when it comes to speakerbuilding, it's crossover design that separates the men from the boys.
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Follow Ups
- Re: Speaker Nominal Impedance or DC Resistance for Xover Calculation - Duke 18:22:35 10/24/05 (0)
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