Crossovers

In simple terms, first order is the simplest and things become more complex as you the order number increases.

You can say roughly that the order number relates to the number of major components in line (series) with each driver. A first order has one part in line with each driver - a cap with the tweeter, and an inductor with the woofer.

Not to get too technical, but a second order crossover adds an inductor in parallel to the tweeter, and a cap in parallel to the woofer. Third order adds another cap in series with the tweeter, and inductor in series with the woofer. Fourth order does the same thing the second order did to the first order on a third order network.

Despite most trying to make this stuff rocket science, it's nowhere near as complicated as we are led to believe. But, watch how many disagree with me here in this thread...

It's not quite as complex as the first post states.

Let's say you have a two way system and you want the crossover point to be 1000 Hz. The crossover separates the frequencies so each driver gets the appropriate ones, below 1000 to the woofer, above 1000 to the tweeter. However, there is no such thing as a perfect crossover so it can't just stop at 1000, (termed a brick wall filter) which in the case of the woofer would be 999 getting through at full strength, but 1001 being completely blocked.

The order tells you how fast the response drops off beyond the cutoff frequency like loontoon says and this is determined by the complexity of the crossover as Trejla points out. The higher the order the faster the signal drops off beyond the cutoff frequency, i.e. the more it acts like a perfect brick wall type filter. So it seems that higher order would be better, but all filters introduce phases shifts, and the higher the order the more complex these phase shifts become, and depending on the design it can also start to have amplitude peaks and dips in it's response that extend into the frequency range it is designed to pass.

The fourth order Linkwitz-Riley that you asked about is a design that some feel has a roll off rate and phase response that is the best compromise between a higher rolloff and flatter phase response. Others feel that anything beyond a simple first order filter introduces too much phase shift to be acceptable.

A full understanding does require a lot of study and a lot of math but the basics are just that, pretty basic.

Okay, well that was all pretty helpful. In any case, it helped answer my underlying question. It seems that many people feel that lower order xovers are the "purest" method, in that due to their simplicity, they "color" the sound the least. Less components = more direct reproduction. I've seen it argued that higher order xovers can introduce more problems than they solve. So, my underlying question was, are higher order/more complicated xovers "bad"? It appears that the answer, like most things audio is, "it depends."

If I've misinterpreted anything here, please let me know. Also, is it logical to assume that as you add more drivers, the crossover necessarily becomes more complicated? (I.e., a 4-way system is going to be more complicated than a two-way)

-Chris

Indeed, it depends...on LOTS of things. BUT...I believe you should not obsess about crossover networks or even make the simplicity/complexity of the crossover a 2nd or 3rd priority. LISTEN to them and go for the best-sounding speaker system you can afford.

You certainly have some overall considerations. Perhaps you're like my friend, a 'worn-out diddeebopper', who values grace under (high sound) pressure above all. He simply walks away from systems, no matter HOW else they sound, if they don't sound at ease while driven VERY LOUDLY*. Or perhaps you value razor-sharp imaging? Or perhaps you value overall soundstaging...ie the mimicking of the concert hall...above all else.

AFTER you buy a speaker, live with it for a while. If you still love it after 6 months or a year, consider improving the crossover components. But first, fall in love with a speaker.

* When he was evaluating speakers this summer, I couldn't be in the same room!
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Actually, I would have no intentions of altering a speaker's crossover, or even basing speaker choice on the crossover type. Ultimately, I'm asking more out of general curiosity, given that there's so many different setups out there.

In the end, I'm going to buy whatever sounds the best to me. But, I like to have SOME understanding of how things work.