Crossovers

If you pay me, I'll put it into laymans terms. $200/hr.

Should take 10-12 hours, to get you the basics so you can build on that foundation.

What you're asking is so broad and vast that quite literally I have offerred you a bargain.

Crossovers are about division thus math is necessary to explain what is happening with any kind of precision.

So what I recommend as "cliff notes" to get you started is get a DIY book like the Loudspeaker Cookbook by vance Dickason or I think martin Collums book touches on the subject too. The fact is very few speakers have text book crossovers in them despite what they claim since most drivers do not not exhibit text book responses and with phenomena like the baffle step etc. this will alter a crossover from stock too.

I'm afraid it takes some time and initiative to get to where even "layman's explanation" can be understood otherwise you will be in a world of mostly false generalizations...worse off than you are now.

Thus I look to your own vision statement and say you will need some DIY experience and some math. Without understanding the basic elements you will be lost on the concepts. You have to meet it atleast half way, learn the math and the relevent vocabulary and the concepts will make more sense. Otherwise you'll just be kidding yourself.

The orders are the degree of turn over at the knee, the point where the cross over rolls your drivers off. The 1st order is 6db/octave, and the 2nd is 12, and 3rd is 18, and 4th order is 24db/octave. The higher the order the sharper the cut-off. The type of filter, Bessel, LinkR, Butterworth, etc describe the circuit apporach to the design. All are quite similiar and different type have different plus and minus's to them. The LinkwitzR, type is often used in D'Appolitto type designs for it's advantage if phase projection.

So without getting into math, that's about as clean as I can tell it.

loon

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